Toceranib was the most widely studied agent, appearing in 41 publications, whereas clinical evidence for several other inhibitors consisted of only a few studies or remained largely preclinical. The researchers searched PubMed on 3 July 2025 for English-language studies published from 1986 through that date, using a strategy adapted from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Eligible studies evaluated tyrosine kinase expression in neoplastic processes and the use of inhibitors in canine in vitro or in vivo settings.

The researchers excluded non-original reports, work without clear ethical approval, studies involving other species, articles not available in open access, publications in languages other than English, and single case reports. Across the 200 eligible publications, the largest clinical dataset contained 1,139 inhibitor-treated cases. Mast cell tumours accounted for 481 cases, carcinomas for 428 and sarcomas for 135.

Smaller groups included 30 insulinomas, 27 chemodectomas, 26 lymphomas, 23 melanomas, five pheochromocytomas and three gastrointestinal stromal tumours. Toceranib appeared in 41 of the 200 publications, followed by masitinib in five, imatinib in four and sorafenib in three. Trametinib appeared in two publications, while vemurafenib, lapatinib and dasatinib appeared in one each.

Sunitinib was included in the broader review because of indirect translational and toxicity evidence, but the search identified no study directly investigating it as treatment for a canine tumour. Toceranib had the broadest clinical record. It inhibits c-KIT, vascular endothelial growth factor receptors and platelet-derived growth factor receptors, allowing it to affect tumour cells as well as vascular and stromal components of solid cancers.

The review reported objective response rates of up to 75% in mast cell tumours, compared with generally lower or more variable rates of 20–45% for carcinomas and sarcomas. Partial responses were also reported with toceranib monotherapy in dogs with apocrine gland anal sac adenocarcinoma. Across the literature, combination regimens generally produced higher partial- and complete-response rates than monotherapy, particularly for toceranib, although the comparison was descriptive rather than the result of uniformly randomised trials.

Masitinib targets c-KIT and platelet-derived growth factor receptors and has been studied mainly in mast cell tumours carrying activating c-KIT mutations. One analysis in the review reported an objective response rate of 70%, comparable to findings for toceranib. Evidence for masitinib in other tumour types was limited to isolated reports in melanoma, lymphoma and selected sarcomas and carcinomas.

Imatinib, which inhibits c-KIT, BCR-ABL and platelet-derived growth factor receptors, has also been evaluated in mast cell tumours and gastrointestinal stromal tumours. Response rates of 60% and 75%, respectively, were reported in the review’s corresponding groupings. Imatinib has additionally been studied in dogs intolerant of or resistant to toceranib or masitinib, often alongside chemotherapy or corticosteroids.

Several less extensively studied inhibitors showed activity in molecularly defined settings. Sorafenib inhibits VEGFR, PDGFR, RAF and KIT; in a first-line study of 13 dogs with hepatocellular carcinoma, it produced a 56% objective response rate. Vemurafenib inhibits BRAF and was evaluated in 24 dogs with BRAF-mutated invasive urothelial carcinoma, of whom 38% achieved a partial response.

Lapatinib, which targets EGFR1 and HER-2, produced a 27.3% objective response rate in one invasive urothelial carcinoma study; higher HER-2 immunohistochemical scores were associated with stronger responses in that analysis. Evidence for trametinib, dasatinib and sunitinib remains preliminary. Trametinib acts on ERK, AKT and mitogen-activated protein kinase pathways and has been investigated in melanoma, carcinoma and sarcoma models.

A canine histiocytic sarcoma study reported a 49.9% response and a progression-free survival of 78 days. Dasatinib showed mild-to-moderate activity in sarcomas and has been explored as a possible option after resistance to other inhibitors. Sunitinib has been examined mainly in experimental studies and off-label cases involving vascular tumours and sarcomas.

The review found that it was generally well tolerated and produced fewer cardiovascular effects than imatinib, but it found insufficient direct clinical evidence and no established dose-escalation schedule for canine solid tumours. Safety findings varied by drug and regimen, although gastrointestinal toxicity was the most frequently reported adverse effect across the class. Toceranib was also associated with proteinuria, thyroid dysfunction and acquired tumour resistance.

Imatinib produced diastolic dysfunction and ventricular early-repolarisation changes in experimental dogs, while masitinib was associated with vomiting, diarrhoea, reduced appetite, lethargy and mild neutropenia. Grade 3 toxicities including hypertension, proteinuria, elevated alkaline phosphatase and lethargy were described with trametinib, vemurafenib and dasatinib. Lapatinib was generally well tolerated, although diarrhoea, rash, fatigue, nausea and vomiting occurred, and vemurafenib produced dermatological lesions in some dogs.

The apparent benefits of combination therapy require caution. Higher response and disease-stability rates, together with longer progression-free survival, were commonly reported when tyrosine kinase inhibitors were combined with chemotherapy, radiotherapy or other treatments. These observations came from studies with different tumour types, disease stages, doses, follow-up periods and response definitions, and the review did not pool them into comparative effect estimates.

Some included studies also lacked overall- or progression-free-survival data. The English-language and open-access eligibility requirements may have excluded unpublished findings or negative reports, further limiting the evidence base. As a result, the review does not establish that combination therapy is superior in every canine solid-tumour setting or support a definitive ranking of most inhibitors.

The authors identified molecular selection as a central unresolved issue. Canine use of tyrosine kinase inhibitors is not generally guided by a validated predictive-marker panel, unlike biomarker-directed treatment in human oncology. Candidate indicators discussed in the literature include KIT mutations, phosphorylated KIT, VEGFR-2, HER-2, HER-2V659E mutations and components of the MAPK pathway.

A proposed receptor panel covering KIT, VEGFR-2, PDGFR-beta, EGFR-1, ERK1/ERK2 and HER-2 requires further validation before it can guide routine drug selection. Prospective controlled trials using standardised veterinary response criteria, serial molecular profiling and clearer toxicity reporting are needed to define which dogs are most likely to benefit from each inhibitor and which combinations offer meaningful clinical advantage. Overall, the review portrays tyrosine kinase inhibitors as an increasingly important but still incompletely validated part of canine oncology.

Toceranib remains the most extensively studied agent, particularly for mast cell tumours, and masitinib has comparable results in that tumour group. Imatinib has a clear role in some KIT-mutated tumours and haematopoietic malignancies. Sorafenib, vemurafenib and trametinib show promise in selected BRAF- or MAPK-associated contexts but require further clinical validation, while lapatinib and dasatinib remain largely experimental.

Sunitinib has potential in vascular or treatment-resistant sarcomas but remains underexplored. The present synthesis supports targeted treatment as an active area of veterinary cancer research, but its descriptive findings cannot yet define uniform efficacy, optimal sequencing or comparative safety across the wider group of canine solid tumours.

Subject of Research: Systematic review of tyrosine kinase inhibitor indications, responses and safety in canine solid tumours

Article Title: Tyrosine kinase inhibitors in canine solid tumours: a systematic review of indications, response and safety

Article References: de Moura, F. B. C., Amorim, R. L., & Fonseca-Alves, C. E. (2025). Tyrosine kinase inhibitors in canine solid tumours: a systematic review of indications, response and safety. Veterinary Oncology, 2(1), Article 21. https://doi.org/10.1186/s44356-025-00036-1

Image Credits: AI Generated

DOI: 10.1186/s44356-025-00036-1

Keywords: canine cancer, tyrosine kinase inhibitors, veterinary oncology, systematic review, mast cell tumours, toceranib, masitinib, targeted therapy, drug safety, canine solid tumours, Tyrosine, kinase

The dog arrived at the veterinary teaching hospital with a hemorrhagic, ulcerative lesion on the back of its right elbow that the owner had first noticed three weeks earlier. Initial cytological examinations, including an impression smear and fine needle aspiration, revealed bacterial infection and atypical cells with concerning features such as marked variation in cell and nuclear size, but no definitive mesenchymal tumor cells could be identified. The atypical epithelioid-appearing cells were interpreted as likely reactive changes associated with the ulcerated wound rather than the underlying malignancy. Empirical antimicrobial and antifungal treatment was started, but the lesion failed to respond and instead rapidly enlarged into a distinct mass.

A biopsy was then performed, and histopathological examination revealed spindle-shaped cells with pleomorphic nuclei within the subcutaneous tissue, consistent with a soft tissue sarcoma. Using the standard three-tiered grading system for canine soft tissue sarcomas, which combines differentiation, mitotic activity, and necrosis into a summed score, the tumor was assigned a grade 2. In general terms, grade 2 soft tissue sarcomas carry a median survival of one to two years and a metastasis rate of up to twenty percent, so the clinical team expected a moderately aggressive but manageable disease. Yet the lesion was progressing faster than such a grade would typically suggest, prompting the clinicians to look deeper.

That deeper look came in the form of 18F-FDG PET/CT, a hybrid imaging modality that merges the anatomical detail of computed tomography with the functional insight of positron emission tomography. The technique relies on a radiolabeled glucose analog that accumulates in tissues with high metabolic activity, a hallmark of many malignant tumors. The dog received an intravenous injection of 239.02 megabecquerels of the tracer, equivalent to 6.29 megabecquerels per kilogram of body weight, followed by a sixty-minute uptake period before scanning. The resulting images showed intense tracer accumulation within the elbow mass, yielding a maximum standardized uptake value of 10.1 and a mean standardized uptake value of 4.6. Critically, no abnormal tracer-avid lesions were detected elsewhere in the body, including the regional lymph nodes, ruling out distant metastasis and confirming the elbow mass as the primary tumor.

Surgical resection was performed approximately two weeks after the PET/CT scan, and the excised tissue underwent definitive histopathological analysis. The results were sobering: the tumor was a poorly differentiated mesenchymal neoplasm with a mitotic count exceeding forty figures per ten high-power fields, producing a summed grade of 3, the most aggressive category. Moreover, the excision was incomplete, with neoplastic cells extending to the deep surgical margin. The preoperative biopsy had therefore underestimated the final tumor grade, while the high fluorodeoxyglucose avidity observed on PET/CT aligned far more closely with the tumor’s true biological behavior. Immunohistochemical staining for desmin and alpha smooth muscle actin, both markers of smooth muscle differentiation, confirmed the diagnosis of subcutaneous leiomyosarcoma, a rare malignancy arising from smooth muscle cells.

Leiomyosarcoma in dogs most commonly originates in visceral organs such as the gastrointestinal tract, liver, or uterus, where it carries a poor prognosis with a reported median survival of roughly ten months. Non-visceral forms, including cutaneous and subcutaneous variants, are far less common and remain poorly characterized. Some researchers argue that subcutaneous leiomyosarcoma should be classified independently from conventional soft tissue sarcomas because of its distinct biological behavior and anatomical location. In human medicine, subcutaneous leiomyosarcoma is considered more aggressive than its purely cutaneous counterpart, with higher local recurrence rates and a worse clinical course, though whether the same distinction holds in dogs remains uncertain due to the scarcity of published cases.

The PET/CT findings in this case are notable when compared against benchmarks from human oncology. In human soft tissue sarcomas, maximum standardized uptake values have been reported at averages of 1.3, 2.7, and 4.5 for grades 1, 2, and 3 respectively, with thresholds of 3.9 for the maximum value and 2.5 for the mean proposed to separate grade 2 and 3 tumors from grade 1. The dog’s maximum value of 10.1 exceeded even the reported human range for grade 3 tumors. The only prior veterinary PET/CT study of canine soft tissue sarcomas documented maximum values between 2.0 and 10.6, but tumor grades were not recorded, limiting direct comparison. A single earlier report of canine leiomyosarcoma, a grade 1 gastric tumor, recorded a maximum value of 6.234, substantially lower than the 10.1 observed in this grade 3 subcutaneous case, suggesting a possible relationship between tracer uptake and histologic grade in this tumor type as well.

The clinical outcome underscored the accuracy of the metabolic signal. Although limb amputation and adjuvant chemotherapy were recommended following the grade 3 diagnosis with incomplete margins, the owner declined both options and opted for palliative care with prednisolone and analgesics. One month after surgery, thoracic radiographs showed no metastatic lesions. But three months postoperatively, the dog developed a cough, and imaging revealed a pulmonary nodule alongside local tumor recurrence at the surgical site. Follow-up imaging three weeks later showed both the size and number of lung nodules increasing. The dog expired six months after surgery, a course consistent with the poor prognosis associated with high-grade tumors and incomplete resection, and one that vindicates the early warning provided by the PET/CT scan.

The case carries important implications for veterinary oncology practice. Because soft tissue sarcomas are biologically heterogeneous, preoperative biopsies can misgrade tumors, with studies showing that pretreatment biopsy does not always reflect the true grade due to intratumoral heterogeneity. Such underestimation can lead to suboptimal surgical planning, inadequate margins, and missed opportunities for aggressive intervention. In this case, the markedly elevated fluorodeoxyglucose uptake served as a functional red flag that the tumor was more dangerous than its biopsy grade implied, supporting the argument for more proactive management such as amputation, adjuvant chemotherapy, and intensified postoperative surveillance when PET/CT reveals high metabolic activity.

The researchers acknowledge limitations inherent to a single case report. Fluorodeoxyglucose is not tumor-specific, and the active purulent inflammation within the ulcerated lesion may have contributed to the elevated uptake, although the authors argue that inflammation alone is unlikely to explain the magnitude of the signal. Additional immunohistochemical markers for smooth muscle differentiation, such as h-caldesmon and calponin, were not evaluated, and Ki-67 proliferative staining was not performed. The suspected pulmonary metastases were never histologically confirmed, though their progressive growth on serial radiographs was highly suggestive. Even so, as the first documented application of 18F-FDG PET/CT to canine subcutaneous leiomyosarcoma, the report opens a window onto a diagnostic approach long established in human sarcoma care and now demonstrating its value in veterinary medicine, where metabolic imaging may soon complement the scalpel and the microscope in deciding how hard to fight a tumor that biopsy alone cannot fully characterize.

Subject of Research: Use of 18F-FDG PET/CT imaging to assess tumor aggressiveness in canine subcutaneous leiomyosarcoma

Article Title: Case Report: 18F-FDG PET/CT for precision assessment of tumor aggressiveness in canine subcutaneous leiomyosarcoma

Article References: Chae, Y., Lee, D., Koo, Y., Yun, T., Kim, H., & Kang, B.-T. (2026). Case Report: 18F-FDG PET/CT for precision assessment of tumor aggressiveness in canine subcutaneous leiomyosarcoma. Frontiers in Veterinary Science, 13, Article 1948200. https://doi.org/10.3389/fvets.2026.1948200

Image Credits: AI Generated

DOI: 10.3389/fvets.2026.1948200

Keywords: 18F-FDG PET/CT, leiomyosarcoma, soft tissue sarcoma, veterinary oncology, tumor grading, diagnostic imaging, canine cancer, standardized uptake value, immunohistochemistry, case report, metabolic imaging, surgical margins

Apocrine gland anal sac adenocarcinoma, abbreviated AGASACA, is a malignant epithelial tumor arising from the anal sacs, the small scent glands tucked on either side of a dog’s anus. It is not common, accounting for roughly 2 percent of all skin tumors and about 17 percent of perianal malignancies in dogs, but it is notorious for two reasons. First, it frequently spreads to regional lymph nodes, sometimes even when the primary tumor is small. Second, it often triggers a paraneoplastic syndrome in which the tumor produces hormone-like signals that drive blood calcium to dangerously high levels, causing increased thirst, weakness, and strain on the kidneys. Dogs typically arrive at the clinic with constipation or straining to defecate, caused by the primary mass or by enlarged metastatic lymph nodes pressing on the rectum.

The patient in this report was a 10-year-old castrated male Maltese weighing just 3.88 kilograms, referred for evaluation of a right anal sac mass and enlarged intra-abdominal lymph nodes. Fine-needle aspiration performed at the referring clinic had already revealed cells with cytological features of malignancy, but a definitive diagnosis would have to wait for histopathology after surgery. The clinical picture was telling: the dog had mild leukocytosis, an elevated ionized calcium concentration of 1.66 mmol/L against a reference interval of 1.16 to 1.40 mmol/L, and metabolic acidosis marked by a raised anion gap, low bicarbonate, and negative base excess. Chest radiographs showed no evidence of pulmonary metastasis, but the abdominal picture remained uncertain.

That uncertainty is exactly where 18F-fluorodeoxyglucose positron emission tomography combined with computed tomography, or 18F-FDG PET/CT, enters the story. The technique exploits a fundamental quirk of cancer biology: malignant cells burn glucose at an accelerated rate. The radiopharmaceutical 18F-FDG is a glucose analog tagged with a positron-emitting isotope of fluorine. Once injected, it is taken up by metabolically hungry tissues, where it becomes trapped after phosphorylation, allowing the PET scanner to map glucose consumption across the entire body. Fused with the anatomical detail of CT, the result is an image that shows not just where structures are, but which of them are biologically active. Uptake is quantified with the standardized uptake value, calculated by dividing the tissue concentration of FDG in megabecquerels per milliliter by the injected activity per gram of body weight. The maximum value within a region of interest, SUVmax, serves as a compact summary of a lesion’s metabolic intensity.

In human oncology, FDG PET/CT is an established staging workhorse, outperforming CT alone for assessing disease extent across many tumor types. In veterinary medicine it has been explored in canine lymphoma, osteosarcoma, mammary carcinoma, cutaneous squamous cell carcinoma, and granulosa cell tumors, but its role in specific tumor entities remains poorly defined. For AGASACA, PET/CT had been mentioned as a staging option, yet no detailed imaging findings or SUV measurements had ever been published. The Korean team set out to fill that gap with a rigorously documented single case.

The imaging protocol was meticulous. The dog was fasted for at least 12 hours, anesthetized with medetomidine and propofol, intubated, and maintained on isoflurane in 100 percent oxygen with mechanical ventilation and intravenous fluids at twice the maintenance rate to support blood pressure. After anesthetic induction, 0.187 mCi/kg of 18F-FDG was injected intravenously. Whole-body CT was acquired on a multidetector scanner at 100 mAs and 120 kVp with 1.25 mm slice thickness, before and after contrast enhancement with iohexol. PET followed on the same scanner after a 60-minute uptake period, with the entire imaging session lasting about two hours. Regions of interest were manually delineated on the fused images, and SUVmax was measured for each suspicious lesion.

The results were striking. CT identified a mass measuring 3.8 by 2.6 by 3.8 centimeters within the right anal sac, an internal iliac lymph node of 3.5 by 2.2 by 1.6 centimeters, and a lumbar aortic lymph node of 1.3 by 1.0 by 1.3 centimeters. PET revealed focally intense FDG uptake in all three: SUVmax 7.3 in the primary tumor, 6.35 in the internal iliac node, and 4.3 in the lumbar aortic node. Crucially, no distant metastatic uptake appeared in the lungs, liver, spleen, or other visceral organs. The dog was classified as Stage IIIa, defined as locoregional nodal metastasis with a maximum metastatic node smaller than 4.5 centimeters and no distant spread. The nodal SUVmax values clearly exceeded the general threshold range of 2.5 to 3.5 used to flag metabolically active lymph nodes as suspicious for metastasis.

Guided by the metabolic map, the surgeons performed an intra-abdominal lymphadenectomy before the right anal sacculectomy, sequencing the procedure to minimize contamination of the abdominal field. The enlarged lumbar aortic node, found adjacent to the aorta at the level of the caudal pole of the right kidney, consisted of two distinct segments that were harvested separately. The enlarged internal iliac node was then excised. During removal of the anal sac, gross invasion of part of the rectal wall was discovered, and the involved portion was resected along with the primary mass. Histopathology confirmed AGASACA in the primary tumor, showing tubular to acinar differentiation, moderate anisocytosis and anisokaryosis, necrosis, and desmoplasia, with a mitotic count of 30 per 2.37 square millimeters and no vascular invasion. The resected lymph nodes contained morphologically similar metastatic adenocarcinoma, with mitotic counts of 35 and 30 in the two lumbar aortic segments and 16 in the internal iliac node, confirming the preoperative Stage IIIa classification.

The postoperative course offered both encouragement and a sobering lesson. The day after surgery, ionized calcium fell to 1.35 mmol/L, back within the reference interval, demonstrating that the paraneoplastic hypercalcemia resolved with removal of the tumor burden. A surgical site dehiscence required a secondary repair, and the dog was discharged 12 days after the initial operation, initially doing well with a good appetite and no fecal incontinence. But at approximately three months, thoracic radiography and abdominal ultrasonography revealed enlargement of multiple intra-abdominal lymph nodes, the rectum was displaced ventrally by a nodal mass, and hypercalcemia recurred at 2.31 mmol/L, signaling progressive nodal metastasis. The owner declined further tumor-directed treatment, and the dog was euthanized on postoperative day 104.

The discussion surrounding the case highlights why the findings matter. Conventional staging for AGASACA relies on abdominal ultrasonography and CT, which judge lymph nodes by size and morphology and say nothing about metabolic activity. Fine-needle aspiration can confirm cytology but is invasive and technically difficult for deep nodes. Lymphatic drainage in AGASACA is also unpredictable: in a prospective pilot study of eight dogs with unilateral tumors, preoperative and intraoperative sentinel lymph node mapping disagreed in four dogs, and contralateral sentinel nodes were identified in four of eight cases. Lumbar aortic involvement, seen here, is less commonly reported than disease in the iliosacral lymphocenter. The primary tumor’s SUVmax of 7.3 sits within the range reported for other canine carcinomas, including adenocarcinomas at 7.6 to 27.0 and malignant mammary carcinomas at 2.97 to 10.01, though cross-study comparisons remain hazardous because scanner hardware and reconstruction algorithms vary. Intriguingly, the internal iliac node showed higher uptake despite a lower mitotic count than the lumbar aortic node, a reminder that FDG uptake reflects cellular composition and glucose metabolism, not proliferation alone. As a single case, the values cannot be generalized, and no disease-specific reference range yet exists for canine AGASACA. But the authors argue the case demonstrates that PET/CT can complement morphology-based imaging by exposing metabolically active nodes at both typical and atypical sites, potentially sharpening preoperative staging and surgical planning. For a cancer that so often hides its true spread until the abdomen is open, that metabolic window may prove to be a genuinely valuable addition to the veterinary oncologist’s toolkit.

Subject of Research: First reported 18F-FDG PET/CT imaging findings and SUVmax values in a dog with apocrine gland anal sac adenocarcinoma and confirmed lymph node metastases

Article Title: Case Report: 18F-FDG PET/CT findings and SUVmax characterization in a dog with apocrine gland anal sac adenocarcinoma

Article References: Shim, B., Kim, Y., & Lee, S. (2026). Case Report: 18F-FDG PET/CT findings and SUVmax characterization in a dog with apocrine gland anal sac adenocarcinoma. Frontiers in Veterinary Science, 13, Article 1977879. https://doi.org/10.3389/fvets.2026.1977879

Image Credits: AI Generated

DOI: 10.3389/fvets.2026.1977879

Keywords: 18F-FDG PET/CT, apocrine gland anal sac adenocarcinoma, SUVmax, veterinary oncology, canine cancer, lymph node metastasis, staging, paraneoplastic hypercalcemia, nuclear medicine, case report, comparative oncology, anal sacculectomy

The Golden Retriever Lifetime Study, launched in 2012 by the Morris Animal Foundation, was designed to untangle the dietary, genetic, and environmental risk factors behind four major canine cancers: lymphoma, hemangiosarcoma, high-grade mast cell tumors, and osteosarcoma. Golden Retrievers were chosen deliberately. Roughly half of all deaths in the breed are attributed to cancer, according to data from the Veterinary Medical Database, and the breed shows a markedly elevated incidence of hemangiosarcoma and lymphoma. Because privately owned dogs were enrolled young, between six months and two years of age, and followed with annual questionnaires, veterinary examinations, and biological sampling, the study captures lifestyle exposures years before any diagnosis is made.

In the new analysis, Dennis Ronzani of Ross University School of Veterinary Medicine and Sarah E. Hooper of Arkansas State University examined the activity and lifestyle questionnaire responses of 3,044 purebred Golden Retrievers across the first seven years of the study. During that window, 277 dogs were diagnosed with cancer, with a median age at diagnosis of 6.1 years. The researchers asked a deceptively simple question: could the exercise habits reported by owners, on their own, distinguish dogs that would develop cancer from those that would not?

Answering that question required overcoming a statistical obstacle that has long discouraged researchers from mining longitudinal cohort data. Standard machine learning algorithms assume that every data point is independently sampled, an assumption shattered by repeated annual measurements of the same dog. Classical models, meanwhile, struggle when the number of observations is smaller than the number of predictors. The team turned to a hybrid method called the BiMM forest, developed by Speiser and colleagues, which combines a generalized linear mixed model with a random forest algorithm. This architecture is specifically built to handle clustered, high-dimensional data with nonlinear relationships and interactions between predictors, making it well suited to serial owner reports spanning multiple years.

The researchers built two models. The first used only questions asked consistently from year zero through year seven; the second incorporated additional questions about the pace and duration of exercise that the Morris Animal Foundation added to the questionnaire starting in year three. The difference in performance was dramatic. The years zero through seven model achieved an overall accuracy of just 68.2 percent, while the years three through seven model reached 80.7 percent accuracy, an F1 score of 74.9 percent, and a fair area under the receiver operating characteristic curve of 0.763. The lesson was clear: knowing how briskly and how long a dog exercises carries far more predictive signal than knowing only which activities it performs.

Ranking the predictors by their mean decrease in Gini importance, the team found that the top variables were year in study, exercise frequency, exercise pace, exercise duration, and the frequency of swimming in both warm and cold weather, followed by the owner-reported overall activity level. Four of the ten most important predictors related directly to the frequency and duration of aerobic activity. Perhaps most surprising, the specific type of exercise and the surface on which it took place ranked low in importance. It was the rhythm and intensity of movement, not the movement itself, that carried the strongest association with cancer status.

The data also revealed a poignant behavioral shift after diagnosis. Owners of dogs diagnosed with cancer reported an 8 to 10 percent increase in exercise frequency in the years following the diagnosis, and a 15.6 to 68.88 percent increase in cold weather swimming, while warm weather swimming declined by 2.0 to 13.9 percent. At the same time, exercise pace and duration fell, with dogs diagnosed in year four showing a 7.8 percent reduction in duration and overall activity levels declining by as much as 15.5 percent. The authors suggest this pattern may reflect veterinary recommendations or owner research into the benefits of exercise for canine cancer patients, mirroring the well-documented phenomenon in which roughly three out of four human cancer survivors meet physical activity guidelines after diagnosis.

The findings resonate strongly with human oncology research. Moderate-to-vigorous physical activity is firmly associated with reduced risk of colon, kidney, liver, and mammary cancers in people, and has been shown to delay cancer onset even in women genetically predisposed to breast cancer. Laboratory studies add mechanistic weight: moderate-intensity exercise inhibits cancer cell proliferation and induces apoptosis in animal models, whereas strenuous activity can, in some contexts, promote tumor growth. Notably, most Golden Retrievers in the study exercised at a brisk walking pace for 10 to 60 minutes per session, which qualifies as moderate intensity under the Physical Activity Guidelines for Americans, yet the total weekly volume often fell short of the 150 to 300 minutes recommended for humans, echoing the finding that three quarters of the US population also fails to meet those guidelines.

The swimming data carry their own intriguing, and cautionary, dimension. Dogs diagnosed with cancer swam slightly more often in cold weather before diagnosis, and cold weather swimming rose sharply afterward, possibly reflecting the growing popularity of aquatic therapy and underwater treadmills for canine rehabilitation. But water quality introduces a potential confound. The US Environmental Protection Agency reports that more than 13 million acres of lakes and ponds are impaired by pollution, and epidemiological studies in humans have linked disinfection by-products such as trihalomethanes in chlorinated pools to increased cancer risk. One prior study even found that dogs with urothelial cell carcinoma were more likely to have swum in pools than cancer-free dogs, a connection the authors say warrants closer investigation.

The study has limitations that its authors acknowledge candidly. Because a data embargo restricted the analysis to the first seven years, many dogs had not yet reached the typical age of cancer diagnosis, and fewer than 10 percent of the cohort had a neoplastic diagnosis, too few to build models for individual cancer types. All cancers were therefore grouped together, and missing body condition score data, available for only some dogs and years, prevented the team from accounting for obesity, itself a known risk factor for certain canine cancers. Still, the authors argue that the results point toward a future in which veterinarians can offer evidence-based exercise guidance for dogs, focused on frequency, duration, and pace rather than activity type, and in which cumulative lifestyle exposures, shaped by owner behavior and environment, take their rightful place in canine cancer risk assessment. As more years of Golden Retriever Lifetime Study data become available, the same machine learning approach may reveal whether these patterns hold for specific tumors, and whether adjusting a dog’s exercise routine could genuinely shift its cancer risk.

Subject of Research: Physical activity patterns as predictors of cancer development in Golden Retrievers

Article Title: Physical activity predictors of cancer in Golden Retrievers: it's about frequency and intensity, not type

Article References: Ronzani, D., & Hooper, S. E. (2025). Physical activity predictors of cancer in Golden Retrievers: it's about frequency and intensity, not type. Veterinary Oncology, 2(1), Article 11. https://doi.org/10.1186/s44356-025-00024-5

Image Credits: AI Generated

DOI: 10.1186/s44356-025-00024-5

Keywords: Golden Retriever, canine cancer, machine learning, physical activity, Golden Retriever Lifetime Study, veterinary oncology, BiMM forest, exercise frequency, exercise intensity, swimming, cancer risk factors, longitudinal study

A research team led by Floryne O. Buishand, Phoebe Y. K. Chan, Dong Xia and Lucy J. Davison at the Royal Veterinary College turned to single-cell RNA sequencing, a technique that reads the gene expression of individual cells rather than averaging signals across a bulk tumour sample. This matters because tumours are not uniform populations; they contain rare subpopulations that may underlie treatment resistance or drive metastasis. Bulk RNA sequencing of canine insulinomas had previously shown that early-stage primary tumours resemble normal pancreas, while late-stage tumours resemble metastatic lymph nodes, but such bulk approaches cannot resolve the internal diversity of a tumour. By profiling cells one by one, the team could detect distinct clusters within each sample and identify marker genes that would be diluted into invisibility in a bulk measurement.

The researchers applied this technology to four insulinoma cell lines spanning three species: canINS, a canine line established from a spontaneously occurring insulinoma; CM, a human insulinoma line; INS-1, a rat line derived from a radiation-induced tumour; and MIN6, a murine line from a transgenic mouse expressing the large T antigen under the rat insulin promoter. Each line carries its own history and its own limitations. CM has large chromosomal rearrangements involving the insulin gene that abolished insulin secretion from early passages. MIN6 and INS-1 both secrete insulin, but their artificial genetic backgrounds do not resemble spontaneous insulinoma. Canine insulinoma, sharing clinical and molecular features with the human malignant disease, has been proposed as a translational model, and earlier work showed that Notch pathway inhibition could target chemoresistant cancer stem cells in both canINS and CM cells.

Between 5,427 and 9,423 cells were analysed per cell line, with a median of 3,606 to 5,964 genes detected per cell and 43,042 to 68,959 mean reads per cell. Computational clustering in R and Seurat revealed five or six distinct cell clusters in each line. All four lines expressed neuroendocrine markers, including ENO2, MAP2 and NCAM1, confirming their neuroendocrine identity, but a striking split emerged in their differentiation status. INS-1 and MIN6 expressed the full panel of islet hormones and mature beta-cell markers tested, including insulin genes Ins1 and Ins2, glucagon, Mafa and Pdx1. In contrast, canINS and CM expressed only ACVR1C, and in the case of CM also MAFA, among the mature beta-cell markers, and neither expressed insulin. Instead, canINS and CM expressed genes normally activated during pancreatic development or in early endocrine progenitors, such as GATA4 and ISL1, which were the only lineage-specific pancreatic progenitor markers detected in canINS.

This differentiation landscape has direct practical value. Dedifferentiation of pancreatic beta cells in adherent monolayer culture, with loss of insulin-secretory capacity, is one of the main obstacles to building representative preclinical insulinoma models. Notably, canINS cells have previously regained insulin expression and secretion when grown in non-adherent conditions, suggesting that their epigenetic memory remains intact and that the absence of insulin expression in monolayer culture does not disqualify a cell line as an insulinoma model. The study’s single-cell maps now allow researchers to make informed choices: INS-1 and MIN6 for questions requiring mature, insulin-producing beta-cell features, and canINS and CM, with their spontaneous-tumour origins, for studies closer to the clinical disease.

The team also examined epithelial-mesenchymal status, a critical axis in cancer metastasis. When cultured in monolayers, pancreatic beta cells undergo epithelial-mesenchymal transition, becoming highly proliferative cells that can re-differentiate into insulin producers. All four lines expressed the epithelial or ductal markers ANXA4, CDH1 and SLC4A4, but vimentin, a mesenchymal marker, was detected in all lines except MIN6 and was significantly higher in canINS and CM than in INS-1. This means canINS and CM contain substantial populations of hybrid epithelial/mesenchymal cells, a state previously observed in prostate, lung and colorectal cancer lines. Hybrid E/M cells are thought to migrate collectively as clusters of circulating tumour cells, enhancing metastatic potential compared with individually migrating cells, making canINS and CM the preferred models for studying how insulinoma cells acquire metastatic behaviour.

Perhaps the most tantalising discovery came from the cross-species comparison. Because single-cell analysis exposes genes robustly expressed in subpopulations that bulk methods would miss, the researchers catalogued the top ten marker genes for each of the 23 clusters identified across the four lines. Nineteen of these clusters were characterised by genes consistently expressed across all cell lines. Filtering for unique cluster markers with plausible cancer-related functions that were conserved across species and expressed in all four lines yielded eight candidate genes: DEPTOR, BICC1, GHR, CCNB2, CENPA, LMO4, VANGL1 and L1CAM. Several of these have documented pro-tumour roles in other cancers. BICC1 drives pancreatic cancer stemness and chemoresistance, L1CAM promotes perineural invasion in pancreatic cancer, CENPA has been implicated in chromosomal instability of pancreatic neuroendocrine tumours, and LMO4 is overexpressed in late-stage pancreatic cancer.

Among these candidates, the growth hormone receptor gene GHR stands out for its translational potential. GHR expression has previously been demonstrated by immunohistochemistry in canine primary insulinomas and their metastases, and growth hormone and insulin-like growth factor 1 expression were increased in metastases compared with primary tumours. This has led to the hypothesis that targeting the GH/IGF-1 axis might inhibit insulinoma proliferation and prevent micrometastatic outgrowth after surgery. Pegvisomant, currently the only clinically available GHR antagonist, is FDA approved for acromegaly, and promising preclinical results have been obtained with pegvisomant and a variant called compound G against pancreatic cancer xenografts, particularly in combination with gemcitabine. Because GHR emerged as a cross-species conserved cluster marker in all four insulinoma lines, the study provides a direct rationale for testing GHR inhibition in these models.

The second major achievement of the study addresses a logistical bottleneck that has long hampered single-cell research on rare tumours. Ideally, fresh patient samples are dissociated into single-cell suspensions immediately upon retrieval to prevent ischaemia-related gene expression changes and RNA degradation, then loaded onto droplet-based platforms within minutes. For rare diseases, where samples arrive sporadically and often far from sequencing facilities, this workflow is difficult to sustain. Cryopreservation offers an obvious solution, but only if freezing does not distort the transcriptomic picture. To test this, the team froze canINS and CM cells in 90 percent fetal calf serum with 10 percent dimethyl sulfoxide, stored them at minus 80 degrees Celsius for four weeks, thawed them, and sequenced them alongside fresh counterparts.

The verdict was emphatically reassuring. Cryopreserved samples yielded five canINS clusters and seven CM clusters, and most clusters matched their fresh counterparts closely, sharing five to nine of the top ten marker genes. Merged datasets showed near-equal distribution of fresh and frozen cells across all clusters, and expression of neuroendocrine, epithelial-mesenchymal, islet hormone and progenitor markers was fully maintained. Differential expression analysis identified 1,395 genes changed in cryopreserved canINS, but only six exceeded a log2 fold change of one, with BTF3, MEI4, NUPR1, FOS and SLC25A6 upregulated; in CM, 1,484 genes were differentially expressed and 29 exceeded the threshold, with TNFRSF12A, CKS1B and PTTG1 upregulated. Only FOS upregulation had previously been linked to DMSO cryopreservation in other cell types. These modest perturbations, the authors note, will need consideration but do not compromise data quality. The message for the field is twofold: insulinoma researchers now have a validated, species-spanning toolkit of cell lines matched to specific experimental questions, and banks of cryopreserved patient samples can finally enter single-cell studies without sacrificing fidelity, reducing assay-based variability and opening the door to larger, multi-centre studies of one of veterinary and human medicine’s most stubborn tumours.

Subject of Research: Single-cell transcriptomic analysis of fresh and cryopreserved multispecies insulinoma cell lines

Article Title: Single-cell transcriptome conservation in a multispecies comparative analysis of fresh and cryopreserved insulinoma cell lines

Article References: Buishand, F. O., Chan, P. Y. K., Xia, D., & Davison, L. J. (2025). Single-cell transcriptome conservation in a multispecies comparative analysis of fresh and cryopreserved insulinoma cell lines. Veterinary Oncology, 2(1), Article 14. https://doi.org/10.1186/s44356-025-00025-4

Image Credits: AI Generated

DOI: 10.1186/s44356-025-00025-4

Keywords: insulinoma, single-cell RNA sequencing, cryopreservation, canine cancer, pancreatic neuroendocrine tumour, beta cells, transcriptomics, comparative oncology, GHR, oncogenes, cell lines, veterinary oncology

The stakes are high because AGASACA behaves in a paradoxical way. Although the primary tumor at the anal sac can be small at diagnosis, metastatic lymph nodes in the sublumbar region can grow large enough to partially obstruct the rectum, creating life-threatening consequences from disease that started in a gland the size of a pea. The disease also tends to progress relatively slowly compared with many other malignancies, which means that long-term locoregional control, rather than a rapid strike against distant spread, is the single most important goal for a successful outcome. Late in the disease course, metastases can also appear in distant organs such as the lungs, but it is the pelvic battlefield where most treatment decisions are won or lost.

Surgery has long been considered the first line of defense. Yet the review makes clear that the surgical landscape is more complicated than many clients realize. Local recurrence of the primary tumor after resection has been reported in anywhere from 4 to 44 percent of cases, with a median time to recurrence ranging from 140 to 374 days. When surgeons attempt to remove metastatic iliosacral lymph nodes, recurrence within the lymphocentrum has been documented in between roughly 12 and 59 percent of cases, sometimes within just six months of the operation. Perioperative complications occur in 12 to 39 percent of patients, and the most feared complication, hemorrhage during lymph node extirpation, affects up to 18 percent of dogs, with mortality reaching 2.2 percent. Critically, the risk of complications climbs sharply when lymph nodes exceed 4.5 centimeters in size, a threshold that should prompt especially careful conversations between veterinarians and owners.

Patterns of treatment failure tell a coherent story across studies. In one investigation of 34 dogs with early-stage disease treated with surgery alone, 21 percent developed local recurrence of the primary tumor at a median of 354 days, and 26 percent developed locoregional metastases at a median of 589 days. A larger study of 161 dogs stratified patients by surgical margins, using the familiar R0, R1, and R2 classification system, and found that only the presence of lymphovascular invasion and an R1 resection, in which tumor cells extend to the cut edge of the specimen, were statistically associated with recurrence. In dogs with massive primary tumors greater than 5 centimeters, none of the stage 2 patients developed lymph node metastasis, while more than half of those presenting with stage 3 disease progressed further. The unifying message is that disease stage at initial treatment mediates the risk of relapse, which implies that adjuvant therapies should be deployed on a risk-based basis rather than universally.

This is where radiation therapy enters the picture, and where the review offers its most nuanced analysis. Conventionally fractionated definitive radiotherapy, or CFDRT, aims to deliver the highest possible dose to residual tumor cells while respecting the tolerance of surrounding normal tissues, typically in 16 to 20 fractions of 2.5 to 3 Gy for total doses of 48 to 50 Gy. The problem is that its clinical role in microscopic AGASACA after surgery remains poorly defined. In a study of 113 variably treated dogs, adjuvant radiation did not produce a significant improvement in survival time, though the small number of irradiated patients and the slow natural history of the tumor may have masked a real effect. Meanwhile, dogs undergoing CFDRT develop moderate to severe acute side effects in organs at risk including the rectum, colon, urinary bladder, skin, and spinal cord, with recovery from acute toxicity taking 23 to 36 days after onset. The therapeutic index, the ratio of benefit to harm, may simply not be favorable enough for this approach in every patient.

The most striking finding in the review concerns hypofractionated radiotherapy for advanced disease. In a study comparing hypofractionated radiation against surgical extirpation of iliosacral lymph nodes in dogs with stage 3b AGASACA, radiation produced significantly longer outcomes: a median progression-free interval of 347 days versus 159 days for surgery, and a median survival time of 447 days versus 182 days. The authors offer a compelling technical explanation rooted in the geometry of radiation planning. When radiation oncologists contour a CT scan, they delineate all visible gross disease as the gross tumor volume, then add margins for subclinical microscopic extension to create the clinical target volume, and finally add further margin for setup uncertainty to create the planning target volume. This means radiation can treat the entire iliosacral lymphocentrum, including microscopic disease threading through the lymphatic network, in a way that no surgeon’s hands can match. Surgery removes individual enlarged nodes; radiation can sterilize the whole nodal basin.

Even the terminology of palliative care may need revision for this disease. Protocols delivering 20 Gy in five daily 4 Gy fractions, often labeled palliative because of their low total dose, have produced median progression-free survival of 289 to 347 days and median survival times of 329 to 447 days in AGASACA patients. For comparison, across a broad range of other tumor types treated with the same 4 Gy by 5 protocol, median progression-free survival was only 4.4 months. AGASACA appears roughly twice as responsive as expected, suggesting the tumor may harbor a low alpha-beta ratio, the radiobiological parameter that determines sensitivity to large fraction sizes, consistent with its slowly proliferating nature. The authors argue that defining treatment intent purely by fraction size and number may be inappropriate when a so-called palliative regimen delivers a year of disease control with mostly mild, grade 1 to 2 gastrointestinal side effects.

Not every advanced technique earns endorsement. Stereotactic body radiotherapy, which delivers ablative doses of 6 to 10 Gy per fraction over 3 to 5 fractions, showed promising survival numbers in small studies, with one report of a 991-day median survival in five dogs. But the largest SBRT study to date, involving 25 dogs treated for metastatic sublumbar lymph nodes, revealed a sobering safety signal: 48 percent of dogs developed late-onset changes in gait and hind limb lameness, including ataxia, paraparesis, weakness, and pain. The authors recommend reserving SBRT for macroscopic disease rather than microscopic tumor beds, and focusing treatment on the nodal region while addressing the primary site surgically. Chemoradiotherapy fares even worse in the evidence hierarchy. The largest dataset, 15 dogs treated with concurrent mitoxantrone, produced a 93 percent rate of severe moist desquamation and a 53 percent rate of clinically relevant late effects, including two dogs euthanized for chronic colorectal toxicity. The review concludes there is insufficient evidence to recommend routine chemoradiotherapy in this disease.

One further clinical pearl concerns hypercalcemia of malignancy, a paraneoplastic syndrome affecting 27 to 34 percent of AGASACA patients that can become an emergency when total calcium exceeds 16 mg/dL. Hypofractionated radiation resolved hypercalcemia in about 31 percent of cases alone, rising to 77 percent when combined with steroids or bisphosphonates, offering a non-surgical route to controlling this dangerous metabolic derangement. Looking forward, the authors call for prospective trials comparing fractionation schemes, systematic imaging-based assessment of response rates, and rigorous studies of patterns of failure. Modern technology, including intensity-modulated radiation therapy and cone beam CT image guidance, should theoretically reduce both acute and late toxicities compared with the older two-dimensional planning used in much of the published literature, though no study has yet confirmed this. For now, the review’s practical bottom line is clear: surgery remains the cornerstone for the primary tumor, radiation deserves serious consideration, and may even be preferred, for advanced nodal disease, and the humble five-fraction protocol may deserve a better name than palliative.

Subject of Research: The role of radiotherapy in treating canine apocrine gland anal sac adenocarcinoma

Article Title: Role of radiotherapy in canine apocrine gland anal sac adenocarcinoma: a review

Article References: Murakami, K., & Rancilio, N. (2025). Role of radiotherapy in canine apocrine gland anal sac adenocarcinoma: a review. Veterinary Oncology, 2(1), Article 12. https://doi.org/10.1186/s44356-025-00028-1

Image Credits: AI Generated

DOI: 10.1186/s44356-025-00028-1

Keywords: canine cancer, AGASACA, radiotherapy, veterinary oncology, hypofractionated radiation, SBRT, iliosacral lymph nodes, hypercalcemia, chemoradiotherapy, surgical oncology, dogs, radiation side effects

Soft tissue sarcomas are malignant, locally invasive tumors arising from mesenchymal cells, and they are among the most common cancers in dogs. Sarcomas account for roughly 10 to 15 percent of malignant tumors in dogs, and about 80 percent of those are soft tissue sarcomas rather than bone tumors. The primary treatment is surgical removal, and the success of local control hinges on whether histological assessment of the margins confirms complete excision. Positive margins leave cancerous cells behind, increasing the risk of local recurrence and the morbidity that comes with it. The stakes are therefore high for getting margin information quickly, ideally while the patient is still on the table.

Optical coherence tomography, or OCT, is the imaging technology at the heart of this effort. It uses near-infrared light to generate real-time, high-resolution images of tissue microstructure, in much the same way ultrasound uses sound waves but with micrometer-scale resolution. Traditional spectral-domain OCT builds images from the intensity of reflected light, revealing depth-resolved structural detail. The technology has been tested for margin assessment in human breast cancer, where it achieved sensitivities of 92 to 100 percent for detecting positive margins, and human clinical trials are underway. The Ohio State team, led by Yuanlong Wang, Laura E. Selmic, and Ping Zhang, has now extended this approach to companion animals with an important upgrade: polarization sensitivity.

Polarization-sensitive OCT, or PS-OCT, is a set of hardware and software extensions that track the polarization state of the light reflected from tissue. This adds contrast mechanisms that ordinary OCT cannot provide. The key property is birefringence, an optical signature that arises from the arrangement of subcellular collagen within tissue and reflects how organized that tissue is. When tissue is damaged, degenerated, or necrotic, its structure breaks down and its birefringence drops. Cancerous tissue, with its disrupted architecture, therefore looks measurably different from healthy fat or muscle under polarization contrast. In prior studies of human breast tissue, PS-OCT demonstrated both qualitative and quantitative differences between cancerous and normal tissue. The system used in the study, a Thorlabs Telesto PS-OCT with a 1300 nanometer central wavelength, 3.5 millimeter imaging depth, and 5.5 micrometer axial resolution in air, synchronously captures traditional OCT images and three polarization metrics: retardation, optic axis, and degree of polarization uniformity, known as DOPU.

The physics behind these metrics is elegant. Two cameras record the reflected light as complex numbers, from which total intensity is computed pixel-wise for the standard OCT image. Retardation measures the difference in optical path experienced by two orthogonal linearly polarized states, calculated as an angle that reflects the ratio of irradiances in each polarization channel. The optic axis describes the orientation of the tissue’s birefringent axis within the plane transverse to the beam, derived from the Stokes parameters that fully characterize the polarization of light. DOPU quantifies the uniformity of polarization within a pixel neighborhood, ranging from 0 to 1, and serves as a regularized measure of how orderly the tissue’s polarization response is. Together with the intensity image, these four channels provide a far richer description of tissue than intensity alone, and the study set out to prove that a neural network could exploit that richness.

The researchers enrolled 48 canine soft tissue sarcoma specimens under an Institutional Animal Care and Use Committee approved protocol, ultimately analyzing 40 after excluding eight tumors that turned out not to be sarcomas. Board-certified veterinary surgeons excised the tumors with margins chosen purely on clinical grounds, and each specimen was wrapped in saline-soaked gauze to prevent drying before imaging. The team scanned the entire surgical margin in B-mode, continuously sweeping the tissue, and captured paired OCT and PS-OCT frames. An expert reviewed image quality, and a pathologist’s evaluation of corresponding histopathology sections provided the gold standard tissue labels. From 140 image pairs, the team cropped 1,553 patches using a sliding window with a 50-pixel stride, resizing each to 224 by 224 pixels to fit the ResNet50 backbone, a convolutional neural network architecture widely used in medical imaging.

The heart of the technical contribution lies in how the four image channels are combined. The team tested two fusion strategies. Early fusion simply concatenates all four images along the channel dimension and feeds them into a single ResNet50 backbone. Joint fusion instead runs four separate backbones, one per metric, and merges their learned feature vectors through a learnable weighted sum before a linear classifier makes the final cancer-versus-normal call. The joint fusion model won decisively, though at the cost of four times the parameters, longer training, and greater vulnerability to overfitting, a trade-off the authors describe explicitly between performance and computational complexity. Training used a 70-15-15 split of train, validation, and test data, with dogs kept whole within a single split to prevent patient overlap, five-fold cross-validation for hyperparameter tuning, random horizontal flips for augmentation, and early stopping against the validation set. Performance was assessed with AUROC, area under the precision-recall curve, F1 score, precision, recall, and accuracy, with uncertainty estimated by bootstrapping the test set 1,000 times.

The results were unambiguous. Both fusion strategies substantially outperformed a baseline model trained solely on traditional OCT images, which the authors attribute to the complementary polarization information. Adding PS-OCT metrics improved AUROC by up to 0.15 for cancerous image classification, and the more polarization metrics included, the greater the gain. The final joint fusion model reached 0.989 AUROC and 91 percent accuracy in detecting positive margins. Notably, the OCT-only baseline achieved the highest recall but at a punishing cost to precision, illustrating why intensity alone is insufficient for reliable intraoperative decisions. Ablation experiments with partial inputs, pairing OCT with just one PS-OCT metric at a time, confirmed that each polarization channel contributes, and that the full multimodal model is the strongest performer on the threshold-agnostic metrics that best reflect underlying discriminative power.

Perhaps the most clinically compelling feature is the diagnostic curve. Rather than simply reporting whether an image contains cancer, the model slides a fine window with a 5-pixel stride across the original image, computes the cancer probability for each patch, and aggregates overlapping predictions into a one-dimensional curve showing the probability of cancer at every horizontal position. In case studies, the curve stayed flat for pure cancerous and pure normal images, and for a mixed image containing tumor in roughly one third of the frame, it rose sharply over the cancerous region and tapered gradually across the margin into fat. This effectively performs a one-dimensional segmentation of the tumor, giving surgeons a map of where cancerous tissue lies rather than a bare yes-or-no verdict, and the window size and aggregation method remain adjustable to clinical preference.

The authors are candid about limitations. The training set is relatively small, and convolutional networks depend heavily on the comprehensiveness of their data, so broader validation is needed before generalizability can be trusted. Raw OCT images carry optical artifacts, motion blur, and noise whose effects on the model remain unquantified, and the fusion strategies explored were deliberately simple, leaving higher-order interactions between polarization metrics unexploited. The model is also far from clinical deployment; explainability, integration into surgical workflows, and careful validation of its effect on surgical outcomes all remain ahead. Still, the trajectory is clear. By teaching a neural network to read the polarization fingerprints that cancer leaves in collagen, this work moves real-time, AI-assisted margin assessment from a promising concept toward a practical tool, one that could spare dogs a second surgery and, if the companion-animal findings translate, may one day help human surgeons answer that oldest of operating room questions with far greater confidence.

Subject of Research: Deep learning-based intraoperative surgical margin assessment for canine soft tissue sarcoma using polarization-sensitive optical coherence tomography

Article Title: Deep learning-assisted surgical margin assessment for canine soft tissue sarcoma based on polarization-sensitive optical coherence tomography

Article References: Wang, Y., Selmic, L. E., & Zhang, P. (2025). Deep learning-assisted surgical margin assessment for canine soft tissue sarcoma based on polarization-sensitive optical coherence tomography. Veterinary Oncology, 2(1), Article 17. https://doi.org/10.1186/s44356-025-00032-5

Image Credits: AI Generated

DOI: 10.1186/s44356-025-00032-5

Keywords: deep learning, polarization-sensitive OCT, optical coherence tomography, soft tissue sarcoma, surgical margins, veterinary oncology, canine cancer, convolutional neural networks, birefringence, cancer imaging, intraoperative diagnosis, ResNet50

The scale of the problem is considerable. Canine oral tumors account for up to 12 percent of all cancers seen in dogs, with melanoma, squamous cell carcinoma, acanthomatous ameloblastoma, and fibrosarcoma representing the most common diagnoses of the oral cavity and pharynx. When these tumors are caught early, wide surgical excision remains the most effective local treatment. But many oral cancers are diagnosed at a locally advanced stage, when complete surgical resection is no longer possible. Radiation and chemotherapy become the fallback options, and while radiation can produce high response rates in tumors such as oral melanoma and squamous cell carcinoma, one-year survival rates for some of the most common oral cancers fall below 50 percent. Novel adjuvant therapies are urgently needed to make those responses last.

The drug at the heart of the study, CB101, is a proprietary hydrogel-based injectable formulation of resiquimod, a molecule known as a toll-like receptor 7/8 agonist. Toll-like receptors sit on the surface or within certain immune cells and act as sentinels for danger signals. In humans, TLR8 is uniquely expressed on myeloid dendritic cells, monocytes, and natural killer cells, making it an attractive lever for pulling the immune system into a fight against cancer. Activating these receptors may disrupt the immunosuppressive microenvironment that tumors build around themselves. Resiquimod itself has never been approved by the FDA, but topical formulations have been tested in human clinical trials for skin diseases and as a vaccine adjuvant, generating an extensive body of toxicology and pharmacology data supporting its safety profile.

The rationale for pairing this immune agonist with radiation rests on a phenomenon called immunogenic cell death. High-dose radiation, such as the 8 Gy per fraction used in some hypofractionated protocols, can kill tumor cells in a way that makes them more visible to the immune system, releasing tumor antigens that dendritic cells can engulf and cross-present to CD8-positive cytotoxic T lymphocytes. Research suggests that doses around 8 Gy per fraction are particularly well suited to synergizing with immunotherapeutics. In principle, this cascade can generate an adaptive, tumor-specific immune response capable of affecting not just the irradiated tumor but also distant, non-irradiated lesions, the so-called abscopal effect. Preliminary mouse data showed that the combination of radiation and CB101 improved local tumor control compared with either treatment alone and elicited such abscopal responses. Injecting the drug directly into the tumor is designed to limit systemic exposure and minimize off-target immune side effects.

Three dogs with histologically confirmed head and neck cancers were prospectively enrolled in the pilot study. Each animal received a baseline CT scan for radiation planning, followed by palliative radiation therapy delivered as four weekly 8 Gy fractions over weeks one through four. CB101 was administered intratumorally at a fixed dose of 10 micrograms in 500 to 1,000 microliters of volume at one-week intervals during weeks two through five, with the first dose given immediately before the second radiation fraction. Treatment planning relied on CT-based software, and dogs were anesthetized and immobilized in vacuum cushions with bite blocks to ensure reproducible setup. A follow-up CT scan at week 12 assessed tumor response, and serial thoracic radiographs at week 24 monitored for distant metastasis. All owners provided informed consent under institutional animal care protocols.

Feasibility proved to be the study’s clearest success. Little to no difficulty occurred during the intratumoral injections, and leakage of the formulation was negligible. Tumors arising from or containing bone were more challenging to infuse; one dog with mandibular fibrosarcoma required both intratumoral and peritumoral administration because of the density of the tumor and its proximity to the normal mandible. Injections were generally performed under general anesthesia for patient comfort, and no pain was noted after the procedure. The volume of each injection was chosen based on the expected ability of the hydrogel to diffuse into the tumor and surrounding tissue, guided by physical examination, CT evidence of bone infiltration, and three-dimensional tumor measurements.

Safety outcomes were equally encouraging. Toxicity was graded using the Veterinary Cooperative Oncology Group criteria and a veterinary radiation morbidity scoring scheme. Only one adverse event was attributable to CB101 itself: a case of grade 1, mild pain during a fourth injection performed under light sedation rather than general anesthesia. Every other adverse event documented was an expected side effect of palliative radiation, and no dog experienced toxicity higher than grade II. One dog developed grade I skin and mucosal toxicity along with grade II ocular toxicity requiring eye drops and antibiotics, an outcome anticipated from the radiation dose distribution, which included a large portion of the left eye. Another dog experienced no toxicity at all.

Tumor responses varied, as expected in such a small and histologically diverse cohort. The dog with oronasal squamous cell carcinoma showed a partial response at week 12 but developed distant progressive disease, first in lymph nodes and then in the lungs, between weeks 12 and 24, and was euthanized 198 days after enrollment. The dog with oral melanoma experienced local progression at week 12 and pulmonary metastasis by week 24, surviving 254 days. The dog with oral fibrosarcoma had stable disease at the week 12 scan, with eventual progression outside the radiation field at week 26 and a survival time of 371 days. All three dogs were free of distant metastases when treatment began.

Intriguingly, serum cytokine analysis revealed negligible changes in the immune signaling molecules the team measured, including TNF-alpha, IL-6, IL-15, interferon-alpha, IL-1 beta, and IL-12p40. The researchers suspect the sampling schedule missed any transient cytokine peaks, which could be expected within hours to three days after dosing rather than a full week later. The absence of clinical signs of cytokine release suggests the weekly 10 microgram dose was well tolerated but may have fallen below a therapeutic threshold. The starting dose was chosen conservatively because a human trial using 12.5 micrograms intralesionally had reportedly triggered cytokine storm and hypotension in some patients. Other veterinary researchers have used far higher resiquimod doses, with a University of Kansas group treating dogs with cutaneous mast cell tumors using doses ranging from 0.07 to 1.36 milligrams and observing one complete response and three partial responses among six dogs.

The Penn team acknowledges several confounders, including the use of NSAIDs in two of the three dogs, which could have either blunted the innate immune response or improved outcomes through COX-2 inhibition, and antimicrobial treatment in one dog, which in human melanoma patients has been associated with worse survival on immunotherapy. Future studies, the authors say, should standardize these medications, sample blood at multiple early time points after injection, and consider analyzing tumor tissue to capture local immune effects within the microenvironment. A dose escalation study appears warranted, and the researchers envision eventually combining TLR agonists with checkpoint inhibitors, an approach that could shift immunologically cold tumors toward hot ones. As academic and industry groups work toward commercializing canine checkpoint inhibitors, this modest pilot study in three dogs may mark the first step of a translational path that runs from the veterinary clinic to human oncology and back again.

Subject of Research: Combining intratumoral resiquimod immunotherapy with hypofractionated radiation therapy in canine head and neck cancer

Article Title: Preliminary evaluation of the safety and feasibility of toll-like receptor ligand CB101 combined with hypofractionated radiation therapy in canine head and neck cancer: a pilot study

Article References: Ghanian, A., DiBona, J., Duda, L., Xu, X., Lukens, J. N., Pearce, T., Ehrhardt, M., Rook, A., Durham, A., Maity, A., & Flesner, B. (2025). Preliminary evaluation of the safety and feasibility of toll-like receptor ligand CB101 combined with hypofractionated radiation therapy in canine head and neck cancer: a pilot study. Veterinary Oncology, 2(1), Article 18. https://doi.org/10.1186/s44356-025-00031-6

Image Credits: AI Generated

DOI: 10.1186/s44356-025-00031-6

Keywords: canine cancer, head and neck cancer, radiation therapy, resiquimod, CB101, toll-like receptors, immunotherapy, intratumoral injection, veterinary oncology, dendritic cells, abscopal effect, pilot study

The research team, led by Luke Borst of Antech Diagnostics and collaborators at Mars Petcare Science and Diagnostics, WALTHAM Petcare Science Institute, and Mars digital technology groups, developed and validated a deep learning system called OncoPetNet. The system is an ensemble of three fully convolutional neural networks built on encoder-decoder architectures with skip connections, a design descended from the U-Net family of image segmentation models. Rather than detecting mitotic figures directly as objects, the model frames the problem as segmentation: it predicts a pixel mask marking candidate dividing cells, and deterministic post-processing steps then convert those masks into coordinates. The encoders draw on EfficientNet-b5, EfficientNet-b3, and SE-ResNext backbones pre-trained on ImageNet, allowing the network to leverage general visual features learned from millions of natural images before fine-tuning on tumor histology.

Deploying such a model in a high-volume diagnostic laboratory required more than a clever network. The team built a production pipeline that runs asynchronously on every whole slide image uploaded to the lab. Each slide first passes through a biopsy slide classifier that decides whether mitotic counting is even appropriate. A non-model tissue detection algorithm then maps the foreground tissue and generates coordinates for the mitotic figure detector, which analyzes overlapping tiles across the entire tumor area. Morphological filters sharpen the predicted masks before a k-d tree based algorithm searches all possible placements of a 2.37 square millimeter square and selects the one containing the most mitotic figures. The final output, delivered to pathologists as annotations on the digital slide, includes both the region of interest and circles around each candidate mitosis.

Validation rested on two ground truth datasets. The first comprised 72 soft tissue sarcomas from the lab’s routine caseload, each confirmed by three pathologists, with consensus expert opinion establishing which AI-flagged candidates were true mitoses. On this dataset, OncoPetNet achieved an F1 score of 0.86, with recall, or sensitivity, reaching 0.97. The second benchmark was the MIDOG++ dataset, a publicly available multi-domain collection built specifically to test how well mitosis-detection models generalize across scanners, stains, laboratories, and tumor types. On 100 canine soft tissue sarcoma images from that set, the model scored an F1 of 0.70, with precision of 0.81 but recall dropping to 0.62. The authors attribute the difference partly to domain shift, since their model was trained on their own scanners and staining protocols, and partly to the low mitotic density of many MIDOG++ images, where a single missed mitosis can crater the score.

With the model validated, the team ran two evaluation studies. The first mimicked routine diagnostics: a single pathologist graded all 72 tumors three ways, manually, with AI assistance, and using AI alone. The results were striking. The AI-only condition averaged 19.9 mitotic figures per case, the AI-assisted condition 14, and the manual condition just 6.26. In other words, AI assistance allowed the pathologist to find about 2.24 times as many mitoses as unaided observation. The pathologist’s role shifted from exhaustive searching to verification: rejecting false positives, which the model produced more often than false negatives, and adding back any true mitoses the network missed. Human oversight measurably moderated the AI’s counts, which is precisely the behavior a safety-conscious deployment would want.

Those increased counts rippled through the grading scheme. Mitotic counts are binned into an ordinal MC score from 1 to 3, which is then summed with scores for tumor necrosis and degree of differentiation to produce the final grade. In the first study, AI-assisted scores migrated upward by one level in 29 percent of cases and by two levels in 6 percent compared with manual counts. Tumor grades followed: 18 percent of tumors moved from grade 1 to grade 2, and 7 percent from grade 2 to grade 3. No tumor migrated two full grades, and no tumor moved downward. The second study, in which nine pathologists organized into three cohorts each reviewed 24 cases both manually and with AI assistance, replicated these findings almost exactly. Across 216 paired observations, AI assistance produced an average of 11.6 mitoses versus 5.31 manually, again a roughly 2.2-fold increase, with grade migration of 15.7 percent from grade 1 to 2 and 5.6 percent from grade 2 to 3.

Efficiency gains were equally consistent. Manual counts took an average of 62.8 seconds per case, while AI-assisted counts took 33.7 seconds, nearly a 1.86-fold reduction. In a busy diagnostic laboratory processing thousands of submissions, halving the time spent on one of the most tedious steps in tumor grading represents a substantial operational improvement. Just as importantly, the AI’s pre-screening of every slide and field relieves pathologists of the cognitive burden of an unhurried, exhaustive search, a practice the authors note is technically required for accuracy but impractical under real-world workloads.

The most consequential findings concern agreement between pathologists. Using intraclass correlation coefficients, the team compared how consistently the nine pathologists rated the same tumors under manual versus AI-assisted conditions. For raw mitotic counts, AI assistance significantly improved agreement in two of the three pathologist trios and overall, lifting the overall coefficient from 0.94 to 0.98. Agreement on MC scores also improved significantly overall. Agreement on which slide to select, measured with Fleiss’ Kappa, rose in all three groups and reached statistical significance in two, reflecting the fact that AI effectively removes the guesswork about where to count. Agreement on final tumor grade showed a consistent upward trend, including a substantial jump in one group from 0.48 to 0.72, but these gains did not reach statistical significance. The authors attribute this dilution to the two remaining subjective parameters, percent necrosis and degree of differentiation, which AI does not yet assess and which continue to drive inter-pathologist variability.

The study’s authors are careful about what these results do and do not prove. The clinical significance of the higher, more sensitive counts remains unexplored: it is possible that current MC score thresholds, calibrated on imperfect manual counts, should be adjusted upward now that detection is better, or that AI-assisted grades will ultimately predict biological behavior more accurately. Testing that will require studies correlating AI-assisted grades with patient outcomes, ideally including clinical follow-up and necropsy data. Extending the approach to quantify necrosis and differentiation objectively would complete the standardization picture. There are also inherent limits to ground truth itself, since even expert consensus on what constitutes a mitotic figure carries some subjectivity, and immunohistochemical markers like phosphorylated histone H3 introduce their own interpretive complications.

What the study does establish is a working template for human-AI collaboration in diagnostic pathology. The machine does what machines do best, exhaustively scanning every slide and field without fatigue, while the human does what humans do best, exercising judgment to reject imposters such as apoptotic bodies, pyknotic nuclei, and inflammatory cells that mimic mitoses. The result is a count that is more sensitive, faster, and more reproducible than either party achieves alone. For veterinary oncology, where soft tissue sarcomas are among the most common canine tumors and grading decisions directly guide surgery and follow-up, that combination could mark the beginning of a genuine standardization of tumor grading, one algorithm-assisted count at a time.

Subject of Research: AI-assisted mitotic counting for standardizing histologic grading of canine soft tissue sarcomas

Article Title: Artificial intelligence-assisted mitotic counts improve efficiency, accuracy, and inter-pathologist agreement: a method toward canine soft tissue sarcoma grade standardization

Article References: Borst, L., Bacmeister, C., Yau, W., Aceino, A., Ranck, R., Labelle, P., Ehrensing, G., Oliveira, F., Myers, C., Willcox, J. L., Ellerby, Z., Haydock, R., Taylor, K., Parkinson, M., Fitzke, M., & Gerdin, J. (2025). Artificial intelligence-assisted mitotic counts improve efficiency, accuracy, and inter-pathologist agreement: a method toward canine soft tissue sarcoma grade standardization. Veterinary Oncology, 2(1), Article 19. https://doi.org/10.1186/s44356-025-00034-3

Image Credits: AI Generated

DOI: 10.1186/s44356-025-00034-3

Keywords: artificial intelligence, deep learning, veterinary oncology, soft tissue sarcoma, mitotic count, tumor grading, digital pathology, inter-observer agreement, canine cancer, convolutional neural networks, histopathology, MIDOG++

Doxorubicin is an anthracycline antitumor antibiotic and one of the most widely used injectable chemotherapeutics in veterinary medicine. It acts on cancer cells through a battery of mechanisms, including DNA intercalation, inhibition of DNA and RNA polymerases, inhibition of topoisomerase II, DNA alkylation, and the generation of reactive oxygen species. That versatility makes it a staple against many canine malignancies, both as a single agent and within multi-drug protocols. But its toxicity profile is equally well known. Gastrointestinal adverse events and myelosuppression, the suppression of bone marrow activity, are the dose-limiting toxicities, and dogs receiving doxorubicin as a single agent experience gastrointestinal side effects more frequently than with most other intravenous chemotherapeutics.

The problem with the current standard lies in its assumptions. Doses of doxorubicin, like many chemotherapies, are calculated using body surface area, a practice originally adopted to normalize doses across species on the grounds that surface area better reflects basal metabolic rate than body weight alone. Yet body surface area cannot account for the factors that actually determine how much drug circulates in a patient: distribution, metabolism, and excretion. The evidence that something is amiss has been accumulating for years. Smaller dogs suffer more severe adverse events when dosed by body surface area, which is why dogs under 15 kilograms are typically treated with a weight-based dose of 1 milligram per kilogram instead. The formula, in short, is imperfect.

Pharmacokinetics offers a way out. Rather than asking how much drug was administered, pharmacokinetic-guided dosing asks how much drug the patient actually absorbed and retained over time, quantified as the area under the drug concentration-time curve, or AUC. Previous work in canine patients demonstrated that predicted doxorubicin AUC correlates with neutropenia, the dangerous drop in neutrophils that marks bone marrow suppression, as well as with total white blood cell counts and the surviving fraction of neutrophils at the nadir, the lowest point of the count. Human medicine has already capitalized on this logic. Pharmacokinetic-guided dosing of docetaxel reduced variability in bone marrow suppression by up to 50 percent, and individualized fluorouracil dosing in metastatic colorectal cancer significantly improved objective response rates compared with conventional dosing.

The Davis team, led by Sridhar Madan Veluvolu together with Robert B. Rebhun, Jaeyoung Kim, and Luke Anthony Wittenburg, built on a tool developed earlier in their laboratory: a limited sampling model that predicts total doxorubicin exposure from just three blood samples. Under the protocol, dogs received a standard 30 milligrams per square meter dose by 20-minute intravenous infusion, and blood was drawn at five, 45, and 60 minutes after the infusion ended. Serum doxorubicin concentrations were measured with a validated liquid chromatography tandem-mass spectrometry assay, linear from 10 to 750 nanograms per milliliter, and plugged into a weighted equation that estimates the AUC over the first six hours. The elegance of the approach is its practicality: three time points instead of an exhaustive sampling series makes prospective clinical use feasible.

The prospective study ran from June 2021 to August 2022 at the UC Davis Veterinary Medical Teaching Hospital, enrolling tumor-bearing dogs at least 15 kilograms in weight with favorable performance scores and no cardiac dysfunction or multidrug-resistance gene mutations. Ten dogs met the criteria, but three were withdrawn after a single dose because of owner-perceived adverse events, leaving seven patients who completed three full cycles of doxorubicin with complete blood counts at baseline and at the seven-day nadir after each dose. Owners filled out standardized questionnaires about gastrointestinal signs after every treatment and were asked to keep their pets on a consistent diet to make those observations as comparable as possible.

The headline result is stark. Measured and dose-normalized doxorubicin concentrations varied nearly tenfold between patients at the sampled time points, and there was no significant correlation between the total milligram dose a dog received and its predicted AUC. When the coefficient of variation was calculated after normalizing for dose, the average within-patient variability across three cycles was just 4.7 percent, while the average between-patient variability was 25.4 percent, a difference that was highly statistically significant. Before dose normalization the within-patient figure was 10.7 percent against 22.5 percent between patients. Notably, the within-patient variability observed in these dogs, ranging from 2.8 to 9 percent, is lower than the 6 to 59 percent reported in humans, while the between-patient variability in dogs was tighter than the 37 to 93 percent seen in human studies.

The model also proved its worth as a predictive instrument. Although no significant relationship emerged between predicted AUC and absolute neutrophil counts across all data points, the picture sharpened when the analysis focused on dogs whose seven-day neutrophil counts were genuinely lower than baseline, suggesting the true nadir had been captured. For those patients, higher exposure correlated significantly with a lower surviving fraction of neutrophils. The limited sampling model, using baseline neutrophil count and predicted AUC together, successfully predicted the absolute nadir neutrophil count with a mean prediction error of just 3.3 percent. Three neutropenic events were captured during the study, two of which occurred at the highest predicted exposures, and one patient who received a 25 percent dose reduction after severe neutropenia subsequently showed a 25 to 32 percent drop in exposure, an encouraging hint that the model tracks dose changes faithfully.

The gastrointestinal findings add a patient-centered dimension. Using owner-reported scores, the researchers found that higher predicted AUC correlated significantly with decreased appetite and increased nausea, though not with vomiting or diarrhea, and no significant relationship emerged for composite gastrointestinal scores. The authors caution that owner scoring of subjective signs carries inherent bias, but the correlations suggest that the patients with the highest drug exposure are also the ones feeling the worst, a pattern that personalized dosing could potentially flatten. The study had clear limitations, including its small size of seven completers, strict eligibility criteria that may not represent the broader population of treated dogs, and unexplored genetic factors, since doxorubicin disposition involves influx and efflux transporters and metabolizing enzymes whose variants in dogs remain poorly characterized.

What comes next is the crucial question of targets. The researchers emphasize that no one yet knows what AUC a dog should hit to maximize tumor response while minimizing toxicity, and that target may differ from patient to patient. In human docetaxel therapy, AUC-guided dose adjustment dramatically increased the proportion of patients within the therapeutic window and improved disease control rates. Neutropenia itself may serve as a double-edged biomarker, since in canine lymphoma it has been associated with longer remission and survival times, hinting that the right amount of bone marrow suppression may signal effective dosing. For now, the Davis team’s message is simple and provocative: the same dose produces wildly different exposures in different dogs, but each dog is remarkably consistent with itself. That consistency is precisely what makes individualized dosing achievable, and the first treatment cycle may be all the information a clinician needs to get there.

Subject of Research: Pharmacokinetic variability of doxorubicin exposure in dogs with cancer using a limited sampling model

Article Title: Comparison of interpatient and intrapatient variability in doxorubicin exposure using a validated limited sampling model in dogs with cancer

Article References: Veluvolu, S. M., Rebhun, R. B., Kim, J., & Wittenburg, L. A. (2025). Comparison of interpatient and intrapatient variability in doxorubicin exposure using a validated limited sampling model in dogs with cancer. Veterinary Oncology, 2(1), Article 24. https://doi.org/10.1186/s44356-025-00038-z

Image Credits: AI Generated

DOI: 10.1186/s44356-025-00038-z

Keywords: doxorubicin, veterinary oncology, pharmacokinetics, limited sampling model, chemotherapy dosing, body surface area, neutropenia, AUC, dogs, adverse events, personalized medicine, canine cancer