When clinicians performed a transurethral resection of the bladder lesion, histopathological examination showed an infiltrative high-grade carcinoma arranged in irregular nests and cords within desmoplastic stroma. Immunohistochemistry told a decisive story: the tumor cells expressed CK20, GATA3, and p63, partially expressed CK7 and Uroplakin III, and were negative for PSA and NKX3.1. That combination is the classic immunophenotype of urothelial carcinoma, the malignancy that arises from the transitional epithelium of the urinary tract. GATA3 is a highly sensitive marker of urothelial differentiation in high-grade tumors, while NKX3.1 is considered a sensitive and specific marker of prostatic origin. The tumor was not a prostate cancer at all. It was bladder cancer that had crossed the bladder neck and invaded the prostate, and the normal PSA level had provided no protection against the misdiagnosis that nearly followed.

Two weeks after admission, the patient underwent radical cystectomy, ileal conduit urinary diversion, and pelvic lymph-node dissection. The postoperative pathology revealed a tumor measuring approximately 4.5 by 4.0 by 1.0 centimeters that had invaded the full thickness of the bladder wall and extended directly into the prostatic stroma and capsule. Fourteen pelvic lymph nodes were negative for carcinoma, but the distal prostatic urethral margin was positive, and the tumor showed both lymphovascular invasion and perineural invasion. The pathological stage was assigned as pT4aN0M0, a designation that reflects the direct, contiguous extension of the bladder primary into the prostatic parenchyma. In the AJCC TNM staging system, prostatic stromal invasion by bladder urothelial carcinoma is classified as pT4a disease, and it is regarded as an important pathological feature of aggressive tumor biology.

PD-L1 immunohistochemistry performed on the primary lesion showed a tumor proportion score below 1 percent and an immune-cell score below 1 percent, indicating low expression. HER2 was negative. Because no neoadjuvant systemic therapy had been given and the final pathology showed pT4a disease with a positive margin, a multidisciplinary discussion concluded that adjuvant systemic therapy was indicated. Current guideline-based options support adjuvant cisplatin-based combination chemotherapy for patients with pT3/4 and/or pN+ disease when no neoadjuvant systemic therapy has been administered, while adjuvant nivolumab is a recommended alternative for high-risk muscle-invasive urothelial carcinoma when cisplatin-based chemotherapy is not feasible or is declined. The planned regimen was gemcitabine at 1,000 milligrams per square meter on days 1 and 8 plus cisplatin at 70 milligrams per square meter on day 1, repeated every 21 days for up to four cycles.

What actually happened next exposes a gap between what oncology guidelines recommend and what patients can tolerate. The patient received only approximately one week of platinum-based chemotherapy plus immunotherapy before treatment was discontinued after renewed shared decision-making, driven by poor tolerance and substantial financial burden. The authors of the case report acknowledge that the inability to deliver complete perioperative or adjuvant systemic therapy is a major limitation of the case and an important context for interpreting what followed. Approximately three months after radical cystectomy, the patient developed low back pain and was evaluated in the oncology department.

Whole-body bone scintigraphy and SPECT/CT fusion imaging demonstrated multiple osteolytic bone metastases involving the L2 and L4 vertebrae and their posterior elements, the bilateral iliac bones, the left acetabular rim, and the right inferior pubic ramus. The distribution is striking: despite negative pelvic lymph nodes at the time of surgery, the cancer had already seeded the axial and pelvic skeleton within a quarter of a year. The authors suggest that occult micrometastases not detectable on routine preoperative imaging may already have been present at the time of cystectomy, and that lymphovascular invasion, perineural invasion, and a positive prostatic urethral margin together indicated highly aggressive tumor biology that routine staging had underestimated.

Soon after the diagnosis of bone metastases, the patient received denosumab at 120 milligrams by subcutaneous injection every 4 weeks to reduce the risk of skeletal-related events, combined with intensity-modulated radiotherapy to the vertebral metastatic lesions at a prescribed dose of 30 Gy in 10 fractions. The choice of denosumab is supported by a phase III randomized controlled trial showing that it was non-inferior to zoledronic acid in delaying skeletal-related events in patients with bone metastases from advanced solid tumors, with a lower incidence of renal toxicity. However, in patients with symptomatic bone metastases, antiresorptive therapy alone is often insufficient to control local pain and maintain skeletal stability, and palliative radiotherapy is usually required as part of comprehensive treatment, consistent with ASTRO evidence-based guidance indicating that palliative radiation can effectively relieve pain associated with bone metastases and help achieve local lesion control.

The deeper lesson of this case lies in the diagnostic pitfall that nearly derailed the workup. Bladder urothelial carcinoma involving the prostate can spread through three major pathways: prostatic urethral mucosal involvement, prostatic ductal involvement, and direct stromal invasion. Among these patterns, stromal invasion represents the most clinically significant form because it reflects tumor infiltration into the prostatic parenchyma and is associated with advanced pathological stage and poorer oncological outcomes. Retrospective analyses of patients with bladder cancer and prostatic involvement have shown that prostatic stromal invasion is closely associated with decreased cancer-specific and overall survival and represents an independent adverse prognostic indicator. Compared with mucosal or ductal involvement alone, prostatic stromal invasion is associated with a higher risk of local recurrence and distant metastasis, and the depth of prostatic involvement independently predicts poor overall survival. Prognosis is determined primarily by the presence of stromal invasion rather than by whether prostatic involvement is contiguous or non-contiguous.

Previous studies have shown that PSA is often normal or only mildly elevated when bladder-derived urothelial carcinoma involves the prostate, which means a normal serum PSA level cannot be used to exclude urothelial carcinoma involving the prostate. Secondary prostatic involvement by bladder urothelial carcinoma has been reported in approximately 12 to 40 percent of radical cystectomy specimens, while primary prostatic urothelial carcinoma is rare, accounting for only 1 to 4 percent of prostate malignancies. Because some high-grade prostatic adenocarcinomas may exhibit solid, nested, or pseudopapillary growth patterns that closely mimic urothelial carcinoma morphologically, particularly in tumors involving the bladder neck or prostatic urethra, careful correlation with immunohistochemical findings is required to establish the correct tumor origin. A single immunomarker is insufficient for reliably distinguishing between these two tumor types, and the combined use of urothelial markers such as GATA3, p63, and Uroplakin III alongside prostatic markers such as PSA and NKX3.1 provides higher diagnostic accuracy than any single marker alone.

From a molecular perspective, urothelial carcinoma is characterized by a highly heterogeneous genomic landscape involving alterations in pathways related to chromatin remodeling, DNA damage repair, cell-cycle regulation, and receptor tyrosine kinase signaling. Comprehensive genomic analyses have demonstrated that muscle-invasive bladder cancer frequently harbors alterations in TP53, RB1, ERCC2, FGFR3, PIK3CA, and ARID1A, which contribute to genomic instability, tumor progression, and biological heterogeneity. Recent molecular classification studies have divided muscle-invasive bladder cancer into distinct subtypes, including basal/squamous and luminal categories, which demonstrate different biological characteristics and prognostic implications. Although comprehensive genomic sequencing was not performed in this patient, the rapid postoperative metastatic progression and extensive pathological risk factors may indicate underlying molecular abnormalities associated with aggressive tumor behavior, and future genomic profiling may help clarify the mechanisms responsible for prostatic stromal invasion and early distant dissemination in this rare subgroup.

For patients with a normal serum PSA level but a mass at the bladder neck or prostatic region, clinicians should remain alert to the possibility of prostatic involvement by bladder-derived urothelial carcinoma, and a routine immunohistochemical panel including GATA3, CK7, CK20, p63, Uroplakin III, PSA, and NKX3.1 should be used early for differential diagnosis. Prostatic stromal invasion combined with lymphovascular invasion, perineural invasion, and a positive surgical margin may indicate highly aggressive disease and an increased risk of early distant metastasis, requiring more active postoperative risk assessment, systemic treatment decision-making, and close follow-up. When perioperative or adjuvant systemic therapy cannot be administered or completed, any deviation from the recommended treatment plan should be thoroughly documented, discussed with the patient, and taken into consideration when interpreting early recurrence. In this case, the early bone metastases are best interpreted as a consequence of both aggressive pathological risk factors and the incomplete delivery of systemic therapy, rather than as a novel diagnostic entity. The patient is currently continuing treatment and follow-up.

Subject of Research: Case report of bladder urothelial carcinoma with prostatic stromal invasion and early postoperative bone metastases

Article Title: Urothelial carcinoma of the bladder with prostatic stromal invasion and early postoperative bone metastases: a case report

Article References: Wang, C., Wang, M., & He, Y. (2026). Urothelial carcinoma of the bladder with prostatic stromal invasion and early postoperative bone metastases: a case report. Frontiers in Urology, 6, Article 1910163. https://doi.org/10.3389/fruro.2026.1910163

Image Credits: AI Generated

DOI: 10.3389/fruro.2026.1910163

Keywords: urothelial carcinoma, prostatic stromal invasion, bone metastases, immunohistochemistry, PSA, radical cystectomy, denosumab, case report, Urothelial, carcinoma, bladder, prostatic

The research, led by Azin Mirzajavadkhan, Christian Chum Him Lai, Margarete K. Akens, Cari M. Whyne, and Chenxi Qian at the University of Toronto and Sunnybrook Research Institute, focused on mixed femoral metastases, a model of the osteolytic and osteoblastic lesions that complicate advanced prostate, breast, and lung cancers. Mixed lesions are particularly treacherous because they combine bone destruction and bone formation within the same anatomical site, producing tissue whose mechanical quality varies dramatically over distances of less than a millimeter. Standard analytical tools, such as bulk Raman spectroscopy or micro-computed tomography, average over those gradients or measure structure without chemistry, leaving the local composition of tumor-adjacent and tumor-distant bone largely unexplored.

Stimulated Raman scattering offers a way around that limitation. Unlike spontaneous Raman spectroscopy, which collects weak inelastic scattering from a laser spot and can require long acquisition times, stimulated Raman scattering uses two synchronized lasers to excite molecular vibrations directly, amplifying the signal by many orders of magnitude. The result is rapid, label-free imaging of specific chemical bonds: amide I and amide III vibrations report on the protein matrix of bone, proline signals trace collagen deposition, phenylalanine marks aromatic amino acid content, and phosphate bands quantify the mineral phase. Because the technique requires no stains, dyes, or decalcification, the same tissue can be interrogated in a near-native state.

To test the approach, the team induced mixed metastases in five- to six-week-old athymic male rats by intracardiac injection of ACE-1 canine prostate cancer cells, a well-characterized preclinical model of osteoblastic-dominant mixed lesions. Twenty-one days after inoculation, the researchers harvested both femora. Sagittal sections of the right femora were processed for histological analysis and stimulated Raman imaging of the organic phase, while undecalcified sections preserved the mineral phase for separate assessment. Regions of interest were then selected within newly formed osteoblastic bone, within bone distant from the tumor, and in distinct samples containing only healthy bone, allowing direct comparison of chemistry across the metastatic landscape.

The measurements revealed a striking biochemical signature in the osteoblastic regions. Compared with healthy bone, the newly formed tumor-associated tissue showed increased signal intensity for amide I, amide III, and proline, indicating enhanced collagen deposition, alongside reduced phosphate and phenylalanine signals, reflecting diminished mineral content and altered protein composition. In practical terms, the tumor-driven bone formation produced a matrix that was collagen-rich but under-mineralized, a combination known to compromise stiffness and fracture resistance. Because mineral-to-matrix ratio is one of the strongest Raman predictors of bone mechanical quality, the finding suggests that even bone that appears to be growing in response to cancer may be structurally inferior to healthy tissue.

Perhaps the more provocative result came from the bone far from the tumor. In regions with no direct tumor involvement, the researchers measured elevated proline and reduced phenylalanine signal intensity, a pattern consistent with systemic perturbation of collagen composition. This supports the study’s central hypothesis: that interactions between tumor and bone influence bone quality beyond the areas of direct tumor involvement. If cancer cells can reprogram the chemistry of bone they have not yet colonized, the implications for fracture risk assessment are significant, because current clinical imaging evaluates lesion geometry rather than the biochemical integrity of the surrounding skeleton.

The findings build on a growing body of Raman-based bone research. Earlier work by several of the same investigators showed that osteolytic and mixed metastases modulate collagen and mineral parameters in rat vertebral bone, and independent studies in mouse models of prostate and breast cancer metastasis demonstrated that tumors alter bone mineral and matrix composition independently of effects on bone architecture. What the new study adds is spatially resolved, quantitative chemical mapping of the organic and mineral phases in mixed femoral lesions, achieved non-destructively and without the exogenous labels that can perturb tissue chemistry.

The technical achievement rests on the maturity of stimulated Raman scattering microscopy itself, which has matured rapidly over the past decade as a biological imaging platform. Recent applications include hyperspectral imaging of microcalcifications in fresh breast biopsies and high-content stimulated Raman histology of human breast cancer, where the technique distinguishes tumor from stroma without section staining. Applying the method to bone required careful handling of the mineral phase, since undecalcified sections preserve hydroxyapatite but are harder to prepare, and the organic phase signals must be disentangled from the strong phosphate background. The Toronto team’s dual-section strategy, using decalcified sections for organic phase imaging and undecalcified sections for mineral assessment, provided a practical route to characterizing both components of the bone matrix.

For clinicians, the study points toward a future where bone quality in metastatic disease could be assessed chemically rather than merely structurally. Skeletal metastases are a leading cause of morbidity in advanced cancer, producing pain, fracture, and spinal cord compression, and treatment decisions, from bisphosphonates to stereotactic body radiation therapy to surgical stabilization, depend on judgments about how much load the compromised bone can bear. A label-free imaging modality that quantifies collagen deposition, mineral content, and protein composition at the microscopic level could eventually inform those decisions, identifying regions of bone that look intact on a CT scan but are biochemically weakened, or vice versa.

The authors caution that the work is preclinical, conducted in a rat model with approval from the institutional animal care committee at University Health Network in Toronto, and that translation to human diagnostics will require further validation. Data supporting the findings are stored at Sunnybrook Research Institute and may be available from the corresponding author under reasonable request. Still, the study establishes stimulated Raman scattering microscopy as a non-destructive tool for detecting spatially resolved biochemical alterations in metastatic bone, and it demonstrates that the chemical footprint of cancer extends beyond the visible margins of the tumor. As the technique matures, the patchwork of metastatic bone, long invisible to conventional imaging, may finally come into focus.

Subject of Research: Stimulated Raman scattering spectromicroscopy reveals biochemical heterogeneity of bone quality in mixed femoral metastases.

Article Title: Bone Quality Heterogeneity in Mixed Femoral Metastases Revealed by Stimulated Raman Scattering Spectromicroscopy

Article References: Mirzajavadkhan, A., Lai, C. C. H., Akens, M. K., Whyne, C. M., & Qian, C. (2026). Bone Quality Heterogeneity in Mixed Femoral Metastases Revealed by Stimulated Raman Scattering Spectromicroscopy. Annals of Biomedical Engineering. https://doi.org/10.1007/s10439-026-04433-x

Image Credits: AI Generated

DOI: 10.1007/s10439-026-04433-x

Keywords: bone metastases, stimulated Raman scattering, bone quality, osteoblastic lesions, collagen, bone mineralization, femur, prostate cancer, Raman spectroscopy, cancer biology, biomedical imaging, Bone

The review, conducted by Jovana Zivanovic of the University Clinical Centre of Serbia and Jules Zhang-Yin of Clinique Sud Luxembourg in Belgium, systematically searched the PubMed database for human studies published between January 2015 and March 2025 that applied quantitative or semi-quantitative analysis to bone SPECT/CT. Following PRISMA 2020 screening principles, the authors identified 150 records, whittled them down through title, abstract, and full-text assessment, and arrived at thirteen primary studies that formed the evidence base for a qualitative synthesis. Reviews, guidelines, and case reports were excluded from the core analysis but used for narrative context. The result is one of the most structured assessments to date of where quantitative bone SPECT/CT stands clinically and where it still falls short.

The technical foundation of the approach is straightforward in principle but demanding in practice. Quantification in SPECT/CT requires converting the counts detected by the gamma camera into absolute activity concentrations within tissue, a process that depends on a complete chain of corrections and calibrations. CT-based attenuation correction compensates for photons lost as they pass through the body, scatter correction removes contamination from deflected photons, and resolution recovery models partially undo the blurring introduced by the collimator. Cross-calibration between the dose calibrator and the camera, typically performed with phantoms, is essential, and recovery coefficients must be characterized for lesions of different sizes because partial-volume effects cause systematic underestimation in small lesions. Once these steps are in place, SUVmax, SUVmean, and SUVpeak can be calculated in a manner analogous to PET/CT, with SUVmax offering sensitivity to focal uptake at the cost of noise vulnerability, SUVmean providing stability but depending heavily on segmentation, and SUVpeak offering a compromise that may prove useful for multicentre follow-up studies.

The most mature clinical application lies in oncology, particularly in distinguishing malignant bone metastases from benign lesions. In one of the included studies, Du and colleagues found that malignant lesions showed significantly higher SUVmax than benign lesions and normal vertebrae, and that an SUVmax threshold of 18.07 identified malignancy with a reported prospective sensitivity of 82.35 percent, specificity of 93.75 percent, and accuracy of 89.80 percent. A separate study in lung adenocarcinoma by Lin and colleagues reported that a cutoff of 11.10 distinguished benign from malignant lesions with 87.70 percent sensitivity and 80.71 percent specificity, while a lower cutoff of 8.135 helped separate CT-negative metastases from normal vertebrae. Notably, the same study found that osteoblastic and mixed lesions had significantly greater SUVmax than osteolytic or CT-negative lesions, underscoring that lesion phenotype itself shapes the numbers.

Yet the review is emphatic that these thresholds cannot be treated as universal constants. Reported SUV cutoffs are influenced by tumour type, uptake time, acquisition and reconstruction parameters, calibration procedures, segmentation methodology, and recovery-coefficient handling, meaning that a value derived on one scanner with one protocol may be meaningless on another. The authors stress that quantitative SPECT/CT should currently be regarded as an adjunct to CT morphology, clinical information, and longitudinal imaging rather than a stand-alone diagnostic test. This caution is reinforced by the risk-of-bias appraisal performed for each of the thirteen studies, which found most to be of moderate quality, with several rated moderate to high risk in domains relating to confounding and external validation, reflecting the predominance of retrospective, single-centre designs with small and heterogeneous cohorts.

Beyond lesion characterization, quantitative bone SPECT/CT shows promise in tracking treatment response over time. Beck and colleagues demonstrated that longitudinal quantitative analysis of bone metabolism achieved almost perfect interobserver agreement, whereas visual analysis produced lower agreement, suggesting that numbers are more reproducible than eyeballs. Gherghe and colleagues showed that quantitative metrics could identify response patterns in metastatic breast cancer that were not always concordant with qualitative interpretation. Volumetric measures such as total lesion activity and skeletal tumour burden, analogous to metabolic tumour volume in FDG PET/CT, may provide global markers of disease extent, and one study by Dittmann and colleagues found that quantitative skeletal tumour burden and uptake parameters measured before radium-223 therapy were associated with patient outcomes, hinting at a prognostic role in bone-targeted radionuclide treatment.

The review also catalogues emerging applications in benign skeletal disease that are less widely appreciated. In mandibular condylar hyperplasia, a developmental deformity causing facial asymmetry, bone SPECT can detect whether the condyle is still actively growing by measuring uptake differences between the two sides, with a difference of roughly 10 percent or more on the affected side taken as evidence of active disease. In fibrous dysplasia, a rare disorder in which normal bone is replaced by immature fibro-osseous tissue, one study of 21 patients found that 18 showed moderate to high MDP metabolism, and a separate approach combining planar skeletal burden scores with lesion SUV values produced disease-corrected metrics that correlated with biological bone turnover markers. Quantitative SPECT/CT has also been applied to vertebral compression fractures, where Wang and colleagues identified an SUVmax cutoff of 9.925 for distinguishing fresh from old fractures, though a previous study reported a higher cutoff of 18.5, illustrating the transferability problem in miniature.

Normal reference values and patient-specific normalization represent another frontier. A study of 221 patients established baseline SUVmax values for normal cervical, thoracic, and lumbar vertebrae and found that males had significantly higher values than females across all three regions. Damian and colleagues investigated whether body weight, age, and CT-derived bone density could improve SUV normalization and found that standard body-weight SUV may overestimate uptake in heavier patients, while age and bone density significantly influenced vertebral uptake. Because many proposed thresholds for metastasis, fracture activity, or degenerative disease rest on SUVmax, wide interpatient variation in background bone uptake could render a single universal cutoff misleading, and future models may need to incorporate lean body mass, bone mineral density, renal function, hydration status, and tracer clearance.

On the hardware front, the review highlights the arrival of ring-configured cadmium-zinc-telluride, or CZT, detector systems that depart radically from the conventional rotating dual-head Anger camera. By arranging multiple stationary or semi-stationary detector modules in a 360-degree configuration around the patient, these systems capture a far greater proportion of emitted photons simultaneously, boosting sensitivity and count statistics. The gains translate into shorter acquisition times, lower administered activities, improved image quality, and better energy resolution that enhances scatter correction. An EANM position paper has argued that full-ring CZT bone imaging may fundamentally change the workflow of bone scintigraphy by making routine tomographic imaging feasible and reducing dependence on planar whole-body acquisitions. Dynamic SPECT acquisitions may even become possible, opening the door to kinetic modelling of tracer uptake rather than static snapshots.

Looking forward, the review identifies artificial intelligence, radiomics, and theranostics as research opportunities rather than established clinical applications. Radiomics could extract features beyond SUVmax and SUVmean to support automated lesion detection and response prediction, while deep-learning-enhanced reconstruction has already demonstrated the ability to maintain quantitative performance in ultra-fast acquisitions, potentially dissolving the traditional trade-off between scan time and image noise. In theranostics, quantitative SPECT/CT could support patient-specific dosimetry and treatment planning with widely available technetium-labelled tracers, though the authors caution that diphosphonate uptake reflects osteoblastic reaction and bone turnover rather than viable tumour burden alone. The overarching message is one of tempered optimism: quantitative bone SPECT/CT is technically feasible, increasingly reproducible, and clinically promising, but prospective multicentre studies with harmonized protocols, standardized calibration, and patient-relevant endpoints are needed before numbers can reliably replace the trained eye.

Subject of Research: Quantitative bone SPECT/CT imaging using standardized uptake values for skeletal disease assessment

Article Title: Quantification in bone SPECT/CT

Article References: Zivanovic, J., & Zhang-Yin, J. (2026). Quantification in bone SPECT/CT. Frontiers in Nuclear Medicine, 6, Article 1941906. https://doi.org/10.3389/fnume.2026.1941906

Image Credits: AI Generated

DOI: 10.3389/fnume.2026.1941906

Keywords: bone SPECT/CT, standardized uptake value, bone metastases, SUV quantification, CZT detectors, nuclear medicine, bone scintigraphy, vertebral compression fracture, fibrous dysplasia, radiomics, theranostics, SPECT reconstruction

The research, led by Tatsuki Ikeda of the Department of Pharmacy at Iwate Medical University Hospital and published in Supportive Care in Cancer, tackles a question that has lingered in oncology for years. Bone-modifying agents, which include bisphosphonates such as zoledronic acid and the RANKL inhibitor denosumab, are well established at reducing skeletal complications in patients whose solid tumors have seeded the skeleton. Randomized trials have repeatedly shown that these drugs delay first skeletal events compared with placebo. What has remained stubbornly unclear, however, is when therapy should begin after the diagnosis of bone metastasis itself, and whether the timing of that first dose changes the downstream risk.

Guidelines from major bodies such as the American Society of Clinical Oncology and the European Society for Medical Oncology recommend bone-modifying agents for patients with bone metastases from solid tumors, but they offer limited specificity about the ideal moment to start. In everyday clinical practice, initiation is shaped by a tangle of competing priorities: staging workups, dental clearance to reduce the risk of osteonecrosis of the jaw, chemotherapy planning, and the simple reality that some patients deteriorate quickly from their systemic disease. The result is wide variation in how quickly patients reach their first infusion or injection, and little evidence to say whether that variation matters.

To answer the question rigorously, the Iwate team turned to a single-institution cohort of patients with solid tumors who received bone-modifying agent therapy for bone metastasis between 2010 and 2024. The central methodological challenge in any study of treatment timing is a statistical trap known as immortal time bias. If researchers simply compare patients who started treatment early with those who started late, counting follow-up time from the diagnosis of bone metastasis, the early starters are guaranteed a period of survival before their treatment begins, because a patient cannot receive a drug before they are alive and under care. That guaranteed event-free window artificially favors the early-treatment group and can manufacture an apparent benefit out of nothing.

The investigators neutralized this bias with a landmark analysis, a technique that fixes a common reference point in time and compares only patients who are still alive, under follow-up, and free of skeletal events at that point. They chose a landmark of six months after the bone metastasis diagnosis. Patients who had already begun bone-modifying agent therapy by the landmark were classified as the Early group, while those who had not yet started were assigned to the Delayed group. Everyone included in the comparison had, by construction, survived at least six months without a skeletal event, ensuring that the groups started on equal statistical footing.

Equal footing, however, requires more than a shared starting line. Patients who begin bone-targeted therapy quickly may differ systematically from those who wait, in tumor type, disease burden, performance status, or the aggressiveness of their cancer. To address this, the researchers performed one-to-one propensity score matching, a method that estimates each patient’s probability of belonging to the early-initiation group based on their baseline characteristics and then pairs similar patients across the two groups. After matching, 134 patients were included in each arm, producing balanced cohorts in which the primary difference was the timing of therapy.

The results were striking. During follow-up after the six-month landmark, skeletal-related events occurred in 86 patients across the matched cohorts. When the researchers modeled the time from the landmark to the first skeletal event, the Delayed group showed a substantially higher hazard: the hazard ratio was 1.82, with a 95 percent confidence interval of 1.16 to 2.84 and a P value below 0.01. In practical terms, patients whose bone-modifying agent therapy had not started by six months after diagnosis faced roughly an 80 percent higher rate of subsequent skeletal complications than their matched counterparts who had already begun treatment, despite being comparable at baseline.

The finding aligns with a growing body of work on the biology of metastatic bone disease. Tumor cells in the skeleton disrupt the normal coupling between bone-resorbing osteoclasts and bone-forming osteoblasts, tipping the balance toward destruction. Bone-modifying agents suppress osteoclast activity, and the earlier that suppression begins, the less time the tumor has to erode cortical bone and compromise the structural integrity of the vertebrae and long bones. Once a vertebral body has collapsed or a fracture has occurred, the damage is largely irreversible, and the clinical focus shifts from prevention to palliation. A therapy that arrives after the skeleton has already failed cannot undo that failure, which may partly explain why delay in this analysis translated into higher event rates even among patients who were event-free at the landmark.

The study’s authors, who also include Satoru Nihei, Kazuki Saito, Junya Sato of Shonan University of Medical Sciences, and senior author Kenzo Kudo, are careful about the limits of the design. As a retrospective, single-institution analysis, the work cannot prove causation in the way a randomized trial would. Unmeasured confounding remains possible: clinicians may have delayed therapy in patients they judged too fragile, too close to death from systemic progression, or already harboring subclinical skeletal damage that later declared itself as an event. The propensity score matching balanced the characteristics that were recorded, but it cannot balance what was never written down. The authors also note that the requirement for patients to remain under follow-up and event-free at six months means the analysis speaks specifically to the subset of patients who live long enough for the timing question to matter, a clinically meaningful group but not the entire metastatic population.

Even with those caveats, the message for clinical practice is difficult to ignore. Prolonged delay in initiating bone-modifying agents after a diagnosis of bone metastasis appears to be associated with a higher subsequent risk of skeletal-related events, and the effect size is large enough to be clinically relevant, not merely statistically detectable. The findings add weight to the argument that once bone metastasis is confirmed, clinicians should move promptly toward initiating bone protection, coordinating the necessary dental evaluation and treatment planning so that protective therapy is not pushed further down the calendar. For patients living with metastatic breast, prostate, or lung cancer, where skeletal involvement is common and often prolonged, the difference between starting bone-targeted therapy within months and waiting half a year or more may shape whether they spend that time walking, or recovering from a fracture. The study does not settle the question of the perfect starting moment, but it draws a clear line: the longer the wait, the greater the risk, and the skeleton keeps score.

Subject of Research: The effect of timing of bone-modifying agent initiation on skeletal-related event risk in patients with bone metastases from solid tumors

Article Title: Timing of bone-modifying agent initiation and skeletal-related event risk in patients with bone metastases from solid tumors: a retrospective landmark and propensity score–matched analysis

Article References: Ikeda, T., Nihei, S., Saito, K., Sato, J., & Kudo, K. (2026). Timing of bone-modifying agent initiation and skeletal-related event risk in patients with bone metastases from solid tumors: a retrospective landmark and propensity score–matched analysis. Supportive Care in Cancer, 34(10), Article 925. https://doi.org/10.1007/s00520-026-11136-5

Image Credits: AI Generated

DOI: 10.1007/s00520-026-11136-5

Keywords: bone metastases, bone-modifying agents, skeletal-related events, bisphosphonates, denosumab, landmark analysis, propensity score matching, immortal time bias, supportive care in cancer, oncology, zoledronic acid, fracture risk

The drugs at the center of the findings, known as antiresorptives, are a cornerstone of modern treatment for bone metastases. Breast cancer that has spread to the skeleton disrupts the normal balance of bone remodeling, tipping it toward excessive breakdown by cells called osteoclasts. This process causes pain, fractures, spinal cord compression and dangerously high calcium levels. Antiresorptive drugs work by suppressing osteoclast activity. Bisphosphonates, such as zoledronic acid, bind to bone mineral and poison the resorption machinery of osteoclasts, while denosumab, a monoclonal antibody, blocks RANKL, the signaling molecule that osteoclasts need to form, function and survive. By dampening bone turnover, these agents reduce skeletal complications and improve quality of life for patients with metastatic disease.

Yet the same mechanism that protects the skeleton carries a paradoxical risk in the jaw. Osteonecrosis of the jaw associated with these medications, abbreviated MRONJ, typically appears as exposed bone in the mouth that fails to heal for more than eight weeks, in patients with no history of radiation therapy to the head or neck. The jawbone is subject to constant mechanical stress from chewing and is frequently challenged by dental infections and procedures. When bone remodeling is profoundly suppressed, the normal repair of tiny injuries in the jaw may be impaired, and dead bone can persist as an open, infection-prone wound. The condition can cause pain, swelling, loose teeth and recurrent infections, and it is notoriously difficult to treat once established.

The Oulu research team designed their study as a retrospective nationwide registry analysis, combining data from the Finnish Institute for Health and Welfare and the Social Insurance Institution of Finland. This approach gave them access to a complete, population-based dataset rather than the selected patient groups seen at single hospitals. The cohort consisted of 652 breast cancer patients with bone metastases who received antiresorptive treatment between 2013 and 2015, and the researchers followed the patients until the end of 2020. That multi-year window matters, because osteonecrosis of the jaw can develop slowly over an extended period, and studies with shorter observation times may substantially underestimate how often it occurs.

The headline figures, 12.6 percent for denosumab alone and 15.3 percent for patients who switched from bisphosphonates to denosumab, are notably higher than many earlier estimates, which often ranged from a few percent in pooled analyses. The Finnish team attributes part of this difference to their long follow-up and their ability to capture diagnoses across the entire national healthcare system. Because the dataset covered all of Finland, the researchers could assess the incidence of the condition and the factors associated with it specifically among Finnish patients with breast cancer that had spread to the bones, something that had never been done before in the country.

Beyond the overall incidence, the study uncovered a telling pattern in the dental records. Dental procedures related to oral infections were associated with the development of osteonecrosis of the jaw. Tooth extraction and root canal treatment, in particular, were linked to a higher risk of the condition. Tooth extraction has long been recognized in the international literature as the most common triggering event for MRONJ, because it creates an open wound in bone whose healing capacity has been chemically dampened. The association with root canal treatment is more novel, but the researchers urge caution in interpreting it: the number of patients in the cohort who underwent root canal treatment was small, and the finding does not establish that the procedure itself causes osteonecrosis of the jaw. It may instead serve as a marker of underlying oral infection or inflammation.

Miika Kujanpää, a doctoral researcher at the University of Oulu, emphasized that the results should not alarm patients into abandoning their cancer treatment. The findings alone do not warrant changing or discontinuing antiresorptive therapy, he noted, and the benefits and potential risks must be assessed on an individual basis. Nor, he stressed, should necessary dental treatment be withheld because of the associations observed. What the results do highlight, according to Kujanpää, is the importance of identifying and adequately treating potential sources of oral infection before starting antiresorptive therapy, and of monitoring oral health continuously throughout the course of treatment. Achieving that, he said, requires close collaboration between oncology and oral healthcare professionals, two specialties that historically have not always coordinated closely.

This preventive message carries real clinical weight. If active infections and non-healing dental problems are resolved before a patient begins denosumab or bisphosphonates, the jaw enters treatment in the best possible condition, with no open wounds to seed necrosis. Once therapy has started, invasive dental work becomes more hazardous, because the suppressed bone turnover persists for months or even years after each dose, particularly with denosumab’s long-acting antibody mechanism. Many international guidelines already recommend a dental examination before initiating antiresorptive therapy, but adherence varies widely, and the Finnish data provide fresh, population-based evidence for why that recommendation matters in everyday oncology practice.

The researchers are careful to frame their study as a beginning rather than an endpoint. They call for further research into how drug dosage, treatment duration and cumulative exposure are associated with osteonecrosis of the jaw, questions that registry data alone cannot fully resolve. More precise information is also needed on the timing of oral infections, dental procedures and the onset of the condition, so that the effects of different contributing factors can be disentangled. And they underline the necessity of sufficiently long follow-up in future studies, since the condition can emerge over an extended period and shorter observation windows risk understating its true incidence.

Perhaps the most consequential question the study raises is also the most practical: how much planned, preventive oral healthcare can actually reduce the risk of osteonecrosis of the jaw? If a structured program of dental screening, infection control and timely treatment before and during antiresorptive therapy can meaningfully lower the incidence observed in Finland, the payoff for patients with metastatic breast cancer could be substantial, sparing them a painful and disabling complication without compromising the bone protection they need. The study was supported by research grants from the Finnish Dental Society Apollonia, and its publication in Clinical Oral Investigations marks a step toward evidence-based, jointly managed care at the intersection of cancer medicine and dentistry. For the hundreds of thousands of women worldwide living with breast cancer that has reached their bones, the message from Finland is clear: the teeth and jaws deserve a place on the treatment plan.

Subject of Research: Incidence and risk factors of medication-related osteonecrosis of the jaw in breast cancer patients with bone metastases receiving antiresorptive treatment

Article Title: Jawbone necrosis in advanced breast cancer: Finnish study highlights the importance of oral health

Article References: Jawbone necrosis in advanced breast cancer: Finnish study highlights the importance of oral health. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: osteonecrosis of the jaw, breast cancer, bone metastases, denosumab, bisphosphonates, antiresorptive drugs, oral health, tooth extraction, registry study, Finland, University of Oulu, Clinical Oral Investigations

The imaging technology at the center of the study is gallium-68 labeled prostate-specific membrane antigen PET/CT, written as [68Ga]Ga-PSMA PET/CT. PSMA is a protein that sits on the surface of prostate cancer cells, and it becomes far more abundant as the disease grows more aggressive. By attaching a radioactive tracer to a molecule that binds PSMA, clinicians can make prostate cancer cells glow on a PET scanner, even when they have seeded only a handful of distant sites. The PET component measures the radiation signal, while the CT component provides anatomical context, so a suspicious hotspot can be matched to a specific bone. The intensity of the signal at the hottest point of a lesion is quantified as the maximum standardized uptake value, or SUVmax, a number that reflects how avidly that tissue grabs the tracer.

That SUVmax number is where the diagnostic dilemma begins. A bone lesion with modest tracer uptake might be a genuine early metastasis, or it might be a benign process such as degenerative change, inflammation, or a healing fracture. Radiologists must draw a line somewhere: above the line, the lesion is called metastatic; below it, benign. Draw the line high, and you risk missing real disease. Draw it low, and benign hotspots get mislabeled as cancer. The Turkish team, led by Mustafa Erol and colleagues, compared two commonly used thresholds head to head in the same patients: a fixed cutoff of SUVmax greater than 3.5, and a relative cutoff defined as SUVmax greater than 1.5 times the activity measured in the blood pool, which adjusts for each patient’s individual background signal.

The study was retrospective and enrolled 108 patients with untreated prostate cancer who had undergone both [68Ga]Ga-PSMA PET/CT and 99mTc-MDP planar bone scintigraphy within 30 days of each other, all for initial staging. To avoid circular reasoning, the researchers did not judge either scan against itself. Instead, they built a best value comparator, or BVC, for each patient and each lesion, combining clinical data, biochemical markers such as prostate-specific antigen, and follow-up imaging to establish the ground truth. Bone metastases were ultimately confirmed in 38 of the 108 patients, or 35.1 percent, a proportion typical of newly diagnosed intermediate- and high-risk disease.

The results were striking at both the patient and the lesion level. Using the stricter SUVmax greater than 3.5 threshold, PSMA PET/CT achieved 97.4 percent sensitivity, 98.6 percent specificity, 97.4 percent positive predictive value, and 98.6 percent negative predictive value. In plain terms, it caught nearly every patient with bone metastases while almost never raising a false alarm. When the researchers loosened the criterion to the relative blood pool threshold, sensitivity and negative predictive value rose to a perfect 100 percent, meaning no metastatic patient went undetected. The price was a modest drop in specificity to 94.3 percent, driven by benign tissue taking up the tracer. Conventional bone scintigraphy, by comparison, managed only 84.2 percent sensitivity and 61.4 percent specificity, meaning it missed roughly one in six patients with bone spread and misclassified a large share of patients without it.

The lesion-level analysis made the contrast even sharper. Among 147 metastases confirmed by the best value comparator, PSMA PET/CT with the blood pool threshold detected every single one, while bone scintigraphy identified only 109 lesions, or 74.1 percent, leaving 38 metastases invisible. The lesions the bone scan missed were disproportionately oligometastatic deposits, meaning small numbers of distant lesions, and osteolytic lesions, which destroy bone rather than provoking the dense new bone formation that technetium tracers highlight. That mechanistic detail explains the old test’s blind spot: 99mTc-MDP accumulates where bone is remodeling in response to tumor, so a lesion that quietly erodes bone without triggering a strong repair response simply does not light up.

What about the threshold question itself? When the two SUVmax criteria were compared directly using exact McNemar testing, the differences were not statistically significant: p equaled 1.00 for sensitivity and 0.25 for specificity. The blood pool threshold offered slightly better sensitivity, the fixed 3.5 cutoff slightly better specificity, but neither advantage reached the level of statistical significance. For clinicians, that is arguably good news, because it suggests PSMA PET/CT’s performance is robust across reasonable interpretation criteria, and radiologists have some latitude in how aggressively they call borderline lesions without dramatically changing the test’s overall accuracy.

The clinical implications reach beyond diagnostic bragging rights. Staging accuracy determines whether a patient receives localized therapy, androgen deprivation combined with radiation, or systemic treatment, and increasingly whether oligometastatic disease is eligible for metastasis-directed therapies. A bone scan that misses 38 of 147 metastatic lesions could leave patients under-staged and under-treated, while its modest specificity can trigger unnecessary anxiety and additional workups. The study’s findings align with and reinforce current clinical guidelines that already favor PSMA PET/CT over planar bone scintigraphy for staging prostate cancer, providing the kind of threshold-specific, head-to-head evidence that guideline committees need when refining recommendations.

The authors are careful about the study’s limits, as any rigorous retrospective single-center analysis must be. The patient cohort, the scanner technology, and the interpretation practices at one institution may not generalize everywhere, and the best value comparator, while carefully constructed, is itself imperfect because no imaging test can achieve perfect ground truth in living patients. The researchers also disclosed that an AI language tool was used only to polish the manuscript’s English, not for study design, data analysis, or interpretation, with the authors retaining full responsibility for the content. Those caveats notwithstanding, the core message stands on solid ground: for detecting bone metastases in untreated prostate cancer, [68Ga]Ga-PSMA PET/CT is not merely an alternative to the traditional bone scan, it is decisively better, and its advantage holds whether radiologists use a fixed SUVmax cutoff or one calibrated to each patient’s blood pool activity. As PSMA-targeted imaging becomes more widely available and less expensive, the planar bone scan’s role in prostate cancer staging looks increasingly like a relic worth retiring.

Subject of Research: Diagnostic accuracy of PSMA PET/CT versus bone scintigraphy for detecting bone metastases in prostate cancer

Article Title: Impact of different SUVmax thresholds on diagnostic accuracy of [68Ga]Ga-PSMA PET/CT versus 99mTc-MDP planar bone scintigraphy in prostate cancer

Article References: Erol, M., Şen, A. E., Tombak, H. A., Şahin, Ö., & Kaya, B. (2026). Impact of different SUVmax thresholds on diagnostic accuracy of [68Ga]Ga-PSMA PET/CT versus 99mTc-MDP planar bone scintigraphy in prostate cancer. BMC Medical Imaging. https://doi.org/10.1186/s12880-026-02902-2

Image Credits: AI Generated

DOI: 10.1186/s12880-026-02902-2

Keywords: prostate cancer, bone metastases, PSMA PET/CT, bone scintigraphy, SUVmax threshold, 99mTc-MDP, gallium-68, diagnostic accuracy, cancer staging, nuclear medicine, oligometastatic disease, medical imaging

Cachexia, the wasting syndrome at the center of this research, is one of the most feared and least understood consequences of advanced malignancy. Characterized by the progressive loss of muscle and, often, fat and bone mass, it affects up to 80 percent of patients with advanced cancer and is implicated in an estimated 20 to 40 percent of all cancer deaths. The syndrome impairs skeletal, diaphragmatic and even cardiac muscle function, erodes tolerance to systemic therapy, and, despite recent progress with experimental agents such as the GDF-15 inhibitor ponsegromab, still has no FDA-approved treatment. As cancer survival improves overall, the clinical burden of cachexia is rising, making the search for its drivers increasingly urgent.

Metastatic bone disease is a common complication across many solid tumors, present in roughly 30 percent of patients with metastatic disease at the time of diagnosis and in as many as 70 percent at autopsy. Clinically, management has traditionally centered on palliating pain and preventing fractures. Yet laboratory work has hinted at broader consequences: tumor–bone interactions can invigorate metastatic growth, and bone-derived factors released during metastatic colonization have been shown to promote muscle wasting in animal models. What has been missing is rigorous clinical evidence that bone metastases are associated with measurable, longitudinal muscle loss in patients.

Kidney cancer offered the researchers an ideal setting to close that gap. Clear cell renal cell carcinoma accounts for nearly 90 percent of kidney cancer cases, and both cachexia and skeletal involvement are frequent: approximately 40 percent of patients develop cachexia, and 30 to 40 percent experience bone metastases during the course of disease. Kidney cancer also carries a relatively favorable prognosis compared with many other solid tumors, providing an extended window in which wasting can influence outcomes and, potentially, be therapeutically targeted.

The study, conducted at Indiana University, retrospectively analyzed 293 adults diagnosed with clear cell renal cell carcinoma between 2010 and 2019. Patients were divided into three groups at diagnosis: those with localized disease, those with metastases outside bone, and those with bone metastases. To quantify body composition over time, the team turned to an artificial intelligence–assisted segmentation platform called Data Analysis Facilitation Suite, which measures skeletal muscle, subcutaneous fat, visceral fat and bone cross-sectional area at the midpoint of the third lumbar vertebra on routine CT scans. Ninety-nine patients had serial scans suitable for longitudinal analysis, allowing the researchers to calculate annualized percent change in each tissue compartment.

The results were striking. At diagnosis, median skeletal muscle cross-sectional area was similar across the three groups, at roughly 151 to 165 square centimeters. Over time, however, the trajectories diverged sharply. Patients with localized disease lost muscle at a median rate of just 0.8 percent per year, and those with extraosseous metastases lost 1.2 percent per year. Patients with bone metastases, by contrast, lost muscle at a median rate of 7.5 percent per year. In multiple variable linear regression adjusting for age, sex, race, chemotherapy, immunotherapy and bone-modifying agents, the presence of osseous metastases was independently associated with an additional 20.9 percent loss of skeletal muscle per year compared with localized disease.

The wasting in bone-metastasis patients was not confined to muscle. Subcutaneous fat declined by 5.1 percent per year in this group, compared with modest changes in the other cohorts, and visceral adipose tissue fell by 15.6 percent per year. Bone cross-sectional area itself decreased by 3.6 percent per year in patients with osseous disease while increasing slightly in the other groups, a pattern consistent with prior reports of bone loss in cancer and suggestive of a systemic musculoskeletal disturbance that extends beyond the sites of metastatic deposits.

Survival analysis reinforced the clinical significance of these measurements. Median follow-up for the cohort was 672 days, during which 144 patients died. One-year overall survival was 88.1 percent for localized disease, 72.3 percent for extraosseous metastases and just 53.3 percent for bone metastases. Five-year survival told a similar story: 80.0 percent for localized disease versus 30.7 percent for patients with skeletal involvement. When the researchers stratified outcomes by the rate of muscle loss, the differences were even more dramatic. Patients losing more than 20 percent of their skeletal muscle per year had a one-year survival of only 30.7 percent and no survivors at five years, compared with one-year survival above 90 percent among patients with little or no muscle loss.

In Cox proportional hazards modeling adjusted for age, chemotherapy, immunotherapy and changes in fat compartments, both bone metastatic disease and skeletal muscle loss remained independently associated with death. Osseous metastases carried a hazard ratio of 15.8 relative to localized disease, while each additional percentage point of annualized muscle loss raised the hazard of death by 2 percent. Notably, 38.2 percent of patients in the osseous group exceeded the 20 percent annual muscle-loss threshold, compared with 13.9 percent of those with extraosseous metastases and only 3.4 percent of those with localized disease.

The authors caution that the study is retrospective, single-institution and subject to the biases inherent in chart review, and that shorter follow-up among patients with metastatic disease may have influenced the longitudinal analyses. Whether bone metastases directly cause muscle wasting or simply mark more advanced systemic disease remains uncertain. Still, preclinical work offers plausible mechanisms: studies in mouse models have shown that transforming growth factor beta released from bone metastases disrupts ryanodine receptor function in muscle, impairing contractility and promoting weakness. If such tumor–bone–muscle pathways operate in patients, kidney cancer, with its relatively long treatment window and high rate of skeletal involvement, could become a rational setting for early trials of cachexia-directed interventions, from structured exercise and rehabilitation to drugs designed to halt the wasting cascade before it becomes irreversible.

Subject of Research: The association between metastatic bone disease, longitudinal skeletal muscle loss and survival in clear cell renal cell carcinoma

Article Title: Metastatic Bone Disease Is Associated With Longitudinal Muscle Loss and Reduced Survival in Kidney Cancer

Article References: Poirier, J.-L., Jines, S. T., Silverman, L. M., Kambrath, A. V., Wurtz, L. D., Zimmers, T. A., & Collier, C. D. (2026). Metastatic Bone Disease Is Associated With Longitudinal Muscle Loss and Reduced Survival in Kidney Cancer. Journal of Cachexia, Sarcopenia and Muscle, 17(5), Article e70400. https://doi.org/10.1002/jcsm.70400

Image Credits: AI Generated

DOI: 10.1002/jcsm.70400

Keywords: kidney cancer, renal cell carcinoma, bone metastases, cachexia, sarcopenia, skeletal muscle loss, body composition, CT imaging, artificial intelligence, survival, cancer wasting syndrome, tumor-bone interaction

The clinical problem at the heart of the study is one of the most persistent frustrations in modern prostate cancer imaging. Prostate-specific membrane antigen positron emission tomography, or PSMA PET/CT, has transformed how doctors stage the disease, offering far better sensitivity and specificity than older techniques such as bone scintigraphy and plain CT. Among the available radioactive tracers, [18F]PSMA-1007 has become especially popular because of its favourable biodistribution: it is cleared through the liver and bowel rather than the urinary tract, allowing a clean view of the prostate and pelvis, and it delivers a high tumour-to-background signal with better spatial resolution and a longer half-life than gallium-68-labelled alternatives.

But [18F]PSMA-1007 carries a well-known trade-off. It produces focal bone uptake that does not correspond to any clear abnormality on the CT component of the scan far more often than other tracers, a phenomenon called unspecific bone uptake. Studies suggest that between roughly 20 and 37 percent of patients have at least one such indeterminate lesion. The stakes of getting the call wrong are high. A false positive can lead to inappropriate upstaging, unnecessary systemic therapy, or even exclusion from potentially curative treatment. A false negative can delay therapy for genuinely metastatic disease. Equivocal findings also trigger extra imaging, prolonged follow-up, higher costs and considerable patient anxiety, and PSMA PET/CT findings have been shown to influence treatment decisions in up to 28 percent of cases.

Two competing strategies have emerged to tame this uncertainty. The first is PSMA-RADS Version 2.0, a five-point structured reporting scale that runs from certainly benign (score 1) to highly suspicious for malignancy (score 5), with the troublesome middle ground labelled score 3. Validation studies have reported excellent accuracy of around 95 to 97 percent across new diagnoses, follow-up and biochemical recurrence settings, along with strong agreement between different readers. The second is the BUMP score, a composite quantitative model that combines three readily obtainable variables: the maximum standardised uptake value (SUVmax) from the PET scan, the mean Hounsfield units (HU) measuring lesion density on CT, and whether the patient was on androgen deprivation therapy at the time of imaging. In its original development and external validation, BUMP achieved area under the receiver operating characteristic curve (AUROC) values of 0.871 and 0.925 respectively, raising hopes that a simple formula could standardise and even automate this difficult judgement.

To test that hope in the real world, researchers led by James Cairns and Salman Arain of Leeds Teaching Hospitals NHS Trust, working with colleagues in Bristol, Newcastle and Oxford, retrospectively analysed [18F]PSMA-1007 PET/CT scans performed as part of routine clinical care at three UK tertiary cancer centres between October 2021 and March 2023. The cohort comprised 130 patients with a median age of 70 years, in whom 412 bone lesions with focal PSMA uptake were identified and segmented by blinded, experienced reporters using a paired-review process. Ground truth for each lesion was established through a composite reference standard combining follow-up imaging, prostate-specific antigen (PSA) kinetics and multidisciplinary clinical consensus, with a median follow-up of 22.8 months.

The biological signal the model relies on was clearly present in the data. Malignant lesions, which made up 60.9 percent of the sample (251 of 412), showed markedly higher radiotracer avidity than benign ones, with a median SUVmax of 7.54 versus 3.53, and greater CT density, with a median of 259 Hounsfield units versus 196. Malignant lesions were also larger, at a median of 12 millimetres compared with 6 millimetres for benign findings. The ribs were the most common site of focal uptake (42.2 percent of lesions), followed by the vertebrae (27.4 percent) and pelvis (15.3 percent). Most patients, 85.4 percent, were scanned for suspected recurrence after treatment, and the majority were not on androgen deprivation therapy at the time of imaging.

Against this backdrop, the BUMP score performed respectably but not brilliantly. Its median value was significantly higher in malignant lesions (0.427) than benign ones (0.08), and ROC analysis yielded an AUROC of 0.812 (95 percent confidence interval 0.636 to 0.931), a modest drop from the 0.87 and 0.92 reported in the original development work, likely reflecting the broader heterogeneity of a real-world multicentre population. Notably, the optimal probability threshold in this cohort, derived using the Liu criterion, was 0.134, considerably lower than the 0.25 cut-off published in the literature. At the locally derived threshold, BUMP achieved a sensitivity of 73.9 percent and a specificity of 80.0 percent, with an F1 score of 0.800; at the literature threshold, sensitivity fell to 62.6 percent while specificity rose to 88.5 percent. The authors emphasise that this threshold shift is a common challenge when generalising quantitative models across institutions and underscores the need for local calibration before clinical deployment.

Human-led structured reporting, by contrast, was in a different league. PSMA-RADS v2.0 scoring achieved an AUROC of 0.980 (95 percent CI 0.952 to 0.993). When scores of 1 to 2 were treated as benign and 4 to 5 as malignant, with the 44 equivocal score-3 lesions excluded, the framework delivered a sensitivity of 98.3 percent and a specificity of 96.2 percent, for a balanced accuracy of 97.3 percent and an F1 score of 0.981. The difference in AUROC between PSMA-RADS and BUMP was 0.1679 (95 percent CI 0.050 to 0.337, p < 0.001). Sensitivity analyses confirmed the result was robust: whether score-3 lesions were counted as benign or malignant, and whether analysis was performed at the lesion or patient level, PSMA-RADS retained its clear advantage, with patient-level AUROCs of 0.966 versus 0.840.

Most telling of all was BUMP’s performance precisely where a quantitative adjunct was supposed to shine: the equivocal lesions. In the 44 lesions that experts had labelled PSMA-RADS 3, the BUMP score’s discriminative power collapsed to an AUROC of just 0.605 (95 percent CI 0.457 to 0.781), barely better than a coin flip. The reason, the authors argue, is that borderline lesions tend to show intermediate SUV values and ambiguous CT density, exactly the inputs BUMP depends on, while expert readers integrate information the formula cannot see: lesion distribution, morphology, anatomical location, overall disease burden and the patient’s pre-test probability. Illustrative cases drove the point home. A vertebral metastasis with a correlative CT abnormality was correctly called malignant by PSMA-RADS but scored benign (0.1) by BUMP, while a hot facet joint from benign arthropathy, with an SUVmax of 7.6, was correctly dismissed by the human reader but flagged as likely malignant (0.61) by the score.

The study’s conclusions come with caveats. The retrospective design introduces selection bias, follow-up duration varied widely, lesion-level statistics were not adjusted for intra-patient clustering, BUMP was not formally assessed for calibration as an absolute probability, and the findings are specific to [18F]PSMA-1007, which has a higher burden of unspecific bone uptake but a lower malignancy rate than other tracers. Ground truth itself relied on multidisciplinary consensus rather than histology, raising the possibility of incorporation bias. Still, the authors see a role for BUMP as a decision-support adjunct, particularly in high-volume centres or for reporters with limited subspecialist experience, and point to more sophisticated radiomics and artificial intelligence models, which incorporate contextual awareness, as the likely next frontier. For now, the message is clear: structured human expertise, in the form of PSMA-RADS v2.0, remains the gold standard for interpreting the skeleton’s ambiguous signals, and quantitative scores should inform, not replace, the expert eye.

Subject of Research: Comparison of the BUMP score and PSMA-RADS v2.0 for characterising focal bone uptake on PSMA-1007 PET/CT in prostate cancer

Article Title: Comparative analysis of PSMA-RADS Version 2.0 versus bone uptake metastatic probability (BUMP) score for characterising focal bone uptake on [18F]PSMA-1007 PET/CT in prostate cancer – a multicentre evaluation

Article References: Cairns, J., Arain, S., Challapalli, A., Stavropoulos, A., Ali, T., Ward, D., Sage, J., Ionescu, G., Willaime, J. M. Y., Frood, R., Bahl, A., Petrides, G., & Scarsbrook, A. (2026). Comparative analysis of PSMA-RADS Version 2.0 versus bone uptake metastatic probability (BUMP) score for characterising focal bone uptake on [18F]PSMA-1007 PET/CT in prostate cancer – a multicentre evaluation. European Journal of Nuclear Medicine and Molecular Imaging. https://doi.org/10.1007/s00259-026-08154-0

Image Credits: AI Generated

DOI: 10.1007/s00259-026-08154-0

Keywords: prostate cancer, PSMA PET/CT, PSMA-1007, bone metastases, BUMP score, PSMA-RADS, unspecific bone uptake, nuclear medicine, diagnostic accuracy, SUVmax, androgen deprivation therapy, structured reporting

The numbers tell a story of two very different diseases hiding under one diagnostic umbrella. Among the 607 patients classified as high-risk under the European Association of Urology classification, fluorine-18 sodium fluoride PET/CT detected bone metastases in 224 individuals, or 37 percent of the group. Yet among the 127 patients with unfavourable intermediate-risk disease and a tumour grade of ISUP grade group 3, exactly one patient, or 0.8 percent, turned out to have metastatic bone involvement. Follow-up data suggested one additional intermediate-risk patient may have harboured a metastasis that the initial scan missed, but even taking that possibility into account, the yield in this subgroup was vanishingly small.

The imaging technique itself is worth understanding, because its physics explains both its power and its pitfalls. After intravenous injection, the fluoride ion travels through the bloodstream in proportion to regional blood flow and exchanges with hydroxyl ions in hydroxyapatite, the mineral scaffold of bone, to form fluoroapatite. This means the signal captured by the PET camera reflects two biological processes at once: bone perfusion and osteoblastic activity, the cellular machinery that lays down new bone. Bone metastases typically provoke exactly this kind of remodelling, which is why they light up brightly on the scan. The catch is that benign conditions, from arthritis to healing fractures, provoke the same response, so interpretation demands experienced readers who can distinguish malignant patterns from incidental noise.

In this study, ten nuclear medicine specialists who collectively analyse more than 3,000 scans per year interpreted the images. Only 24 of the 734 scans, roughly 3 percent, were classified as equivocal, and two experts blinded to the original reports reanalysed each of those cases to reach a consensus diagnosis, concluding that 20 of the 24 patients did not have bone metastases. That low equivocal rate stands in sharp contrast to the older technology that shaped current guidelines. Planar bone scintigraphy using technetium-99m labelled diphosphonates, the workhorse of previous decades, produces far more ambiguous results. In one retrospective study of 853 patients cited by the Danish team, 16 percent of scans were equivocal; in another of 703 patients, the figure reached 42 percent, forcing a cascade of additional imaging.

To establish how trustworthy the PET findings actually were, the researchers constructed a rigorous reference standard. A nuclear medicine specialist reviewed all available follow-up imaging alongside clinical records, and when the picture remained unclear, a urologic specialist weighed the full clinical data set. Evidence supporting metastatic disease ranged from histologic verification and confirmatory MRI or PSMA PET/CT findings down to patterns of increasing fluoride uptake or newly emerging lesions consistent with treatment failure. Evidence against included undetectable prostate-specific antigen after radical prostatectomy, negative complementary imaging, and consistently negative follow-up scans paired with stable or falling PSA in the absence of systemic therapy. For the 689 patients, 94 percent of the cohort, in whom this process yielded a conclusive verdict, fluorine-18 sodium fluoride PET/CT achieved a sensitivity of 0.90 and a specificity of 0.99, figures the authors describe as consistent with the best previous estimates.

Within the high-risk group, the analysis confirmed what clinicians have long suspected about the biology of prostate cancer’s spread to bone. Higher PSA levels, more advanced clinical tumour stage, and higher ISUP grade groups each carried independently increasing odds of metastasis in multivariate logistic regression, with the three variables adjusted for potential confounding. This dose-response relationship across the classic risk markers reinforces that bone imaging is genuinely informative precisely where the disease is most aggressive. The problem, the authors argue, is that guidelines extrapolated from planar bone scintigraphy-era evidence have never been systematically revalidated for modern scanners, and the diagnostic pathway itself has shifted underneath them, with MRI-targeted biopsies now upgrading many tumours into higher grade categories and shifting patients between risk groups.

The single intermediate-risk patient with a confirmed metastasis illustrates how subtle these cases can be. The scan revealed a single sclerotic lesion in the right pubic bone with avid fluoride uptake, subsequently confirmed by gallium-68 PSMA-11 PET/CT. The patient underwent radical prostatectomy as part of a clinical trial for oligometastatic disease, and histopathology of the removed prostate showed grade group 5 disease, a reminder that grade can be underestimated before the whole gland is examined. The second intermediate-risk patient, whose initial scan showed no lesions, received curative radiotherapy and 17 months of medical castration before treatment was stopped due to side effects; three and a half years later, a follow-up sodium fluoride PET/CT revealed a suspicious lesion in the left pubic bone, and the original scan was retrospectively classified as false-negative.

How do these results square with the newer contender in the field, PSMA PET/CT? A retrospective multicenter study of 396 intermediate-risk patients with grade group 3 disease, examined with four different PSMA radioligands, found bone metastases in 4 percent overall, but the rate varied dramatically by tracer: 21 percent with fluorine-18 PSMA-1007 against just 3 percent with gallium-68 labelled agents. That discrepancy matters because fluorine-18 PSMA-1007 is known to produce uptake in non-specific bone lesions, meaning some of those positives were likely false. A separate study of 1,253 consecutive men staged with gallium-68 PSMA-11 PET/CT detected bone metastases in only 3 percent of 638 intermediate-risk patients. Both figures align closely with the Danish sodium fluoride results, and they carry a practical warning: when the pretest probability of bone involvement is this low, isolated PSMA-avid bone lesions should be interpreted with considerable caution, since non-specific uptake may account for a substantial share of positive findings.

The authors are candid about the limitations that temper their conclusions. The retrospective, single-center design introduces potential selection bias and limits control over imaging indications and follow-up procedures. The reference standard relied on follow-up rather than histology in most cases, leaving room for misclassification, and systemic treatment started after the index scan may have masked metastases that would otherwise have declared themselves. The sensitivity estimate in the intermediate-risk subgroup rested on just two positive patients, making it statistically imprecise. Biopsy technique also varied across the cohort, with some men receiving systematic ultrasound-guided biopsies and others MRI-targeted sampling from March 2019 onward, a heterogeneity that may have influenced ISUP grading and therefore risk stratification itself.

Even with those caveats, the central message is hard to escape. Fluorine-18 sodium fluoride PET/CT performs superbly where it matters most, catching bone metastases in more than a third of high-risk patients with sensitivity and specificity approaching the ceiling of what imaging can achieve. But for men with unfavourable intermediate-risk disease and grade group 3 tumours, the scan found metastases in one patient out of 127, and the authors conclude that routine use in this subgroup appears to have limited clinical value. As hospitals worldwide weigh the cost, radiation exposure, and logistical burden of staging imaging against genuine benefit, this study offers a data-driven argument for narrowing the net, reserving advanced bone imaging for the patients in whom the disease is truly likely to have already reached the skeleton.

Subject of Research: Diagnostic accuracy of fluorine-18 sodium fluoride PET/CT for detecting bone metastases in newly diagnosed prostate cancer

Article Title: Risk of bone metastases on [18F]NaF PET/CT in 734 patients with newly diagnosed prostate cancer

Article References: Madsen, C., Zacho, H. D., Bisbjerg, R., Fuglø, D., & Østergren, P. B. (2026). Risk of bone metastases on [18F]NaF PET/CT in 734 patients with newly diagnosed prostate cancer. European Journal of Nuclear Medicine and Molecular Imaging. https://doi.org/10.1007/s00259-026-08148-y

Image Credits: AI Generated

DOI: 10.1007/s00259-026-08148-y

Keywords: prostate cancer, bone metastases, NaF PET/CT, PSMA PET/CT, bone scintigraphy, diagnostic accuracy, intermediate-risk, ISUP grade group, EAU guidelines, PSA, nuclear medicine, staging

The radioligand at the center of the study, [177Lu]Lu-P15-073, is a lutetium-177-labeled bisphosphonate. Bisphosphonates are compounds with a natural affinity for regions of active bone remodeling, where they bind to hydroxyapatite mineral. Because metastatic lesions in bone typically trigger intense local bone turnover, radiolabeled bisphosphonates accumulate preferentially at these sites, allowing the beta-minus radiation emitted by lutetium-177 to irradiate tumor cells embedded in the skeletal niche while sparing most healthy tissue. The companion imaging agent [68Ga]Ga-P15-073, labeled with the positron emitter gallium-68, allows clinicians to visualize where the therapeutic compound will lodge before committing to treatment, a theranostic pairing familiar from the success of prostate-specific membrane antigen-targeted radioligand therapy in prostate cancer.

The study’s authors set out to investigate an underappreciated dimension of this approach. The efficacy of bone-seeking radiopharmaceuticals, they argued, depends not only on radiation dosimetry, the traditional calculus of how much dose reaches tumor versus healthy organs, but also on the biological stability of the skeletal microenvironment itself. High-dose beta irradiation from [177Lu]Lu-P15-073, they hypothesized, might damage the bone niche in ways that inadvertently promote cancer progression. To test this, the team built an intratibial xenograft model, implanting human A549 lung adenocarcinoma cells directly into the tibia of experimental animals, and paired the model with quantitative proteomics to map, molecule by molecule, how the bone microenvironment responded to the therapeutic radiation.

The results revealed a sobering pattern. Although the radioligand showed sustained retention in the implanted bone tumors, confirming that the agent effectively targets skeletal lesions, animals receiving radioligand monotherapy fared worse than expected. At the experimental endpoint, the monotherapy group carried a higher pulmonary metastatic burden, meaning more lung cancer colonies had taken root in the lungs. Proteomic and structural analyses pointed toward a mechanism: the therapeutic radiation was associated with osteoclastogenesis, the formation and activation of the bone-resorbing cells that dismantle skeletal matrix, and with lipid-metabolic reprogramming in the bone microenvironment, marked by upregulation of the proteins FABP4 and PLIN1. These molecular shifts were accompanied by cortical bone degradation and, ultimately, by increased seeding of metastases in the lungs.

The lipid biology here is particularly intriguing. FABP4, a fatty acid-binding protein, and PLIN1, which coats intracellular lipid droplets, are classic markers of adipocyte differentiation and lipid accumulation. Their upregulation suggests that radiation reshaped the metabolic character of the bone niche, potentially enriching it with lipid-laden cells of the sort known to provide metabolic support to disseminated tumor cells. In the vicious cycle of bone metastasis, tumor-driven and treatment-driven osteolysis releases growth factors stored in bone matrix, fueling tumor growth further, while the resorbed architecture weakens the skeleton and opens routes for cancer cells to escape into circulation and colonize distant organs such as the lungs.

Having identified the mechanism, the researchers tested a mechanistically driven countermeasure: concurrent inhibition of RANKL, the receptor activator of nuclear factor kappa-B ligand. RANKL is the master signaling molecule that drives osteoclast differentiation and activation, and blocking it is already a clinically validated strategy for protecting bone in patients with metastatic disease. The anti-RANKL antibody denosumab is widely used to prevent skeletal-related events in cancer care. In the preclinical experiments, adding RANKL blockade to the radioligand regimen attenuated the radiation-associated osteoclastogenesis, blunted the lipid-metabolic reprogramming, and preserved skeletal integrity, effectively holding the bone niche together while the radiation attacked the tumor.

The impact on clinically meaningful outcomes was substantial. Pulmonary metastasis developed in only 25 percent of animals receiving the combination, compared with 87.5 percent of those treated with radioligand monotherapy and 75 percent of controls. Median survival also increased significantly, exceeding 50 days in the combination group versus 37.5 days in the monotherapy group, a difference the authors report as statistically significant with a P value below 0.01. In a disease context where bone metastases of lung cancer carry a bleak prognosis and few effective options, a treatment combination that both keeps the skeleton intact and curbs distant spread represents an unusually encouraging preclinical signal.

The study also extended into the clinic, albeit in a preliminary way. The team analyzed imaging data and early outcomes from a registered cohort of patients with bone-metastatic lung cancer, drawing on the clinical trial of lutetium-177-labeled phosphonates registered as ChiCTR2300077313 in November 2023. Translational morphological imaging showed heterogeneous remodeling patterns across treated lesions: a representative lesion in a patient exposed to denosumab, the RANKL inhibitor, showed signs of osteogenic repair, with new bone formation healing the damaged architecture, while a representative lesion treated with radioligand alone displayed progressive osteolysis, the characteristic moth-eaten destruction of bone. Although these clinical observations are preliminary and the human cohort was small, they mirror the biology observed in the animal models and lend translational weight to the combination hypothesis.

The authors are careful to frame their conclusions as associations and rationale rather than proof. Radiation-driven osteolysis and lipid reprogramming, they write, may represent factors that limit the efficacy of bone-targeted monotherapy, and concurrent RANKL inhibition may help stabilize the skeletal microenvironment and reduce the pulmonary metastatic burden observed in this model. The findings, they conclude, provide a preclinical rationale for further evaluation of RANKL inhibition alongside bone-seeking radioligands. Such measured language is appropriate for a study whose human component is exploratory, and the registered trial will be the venue in which the strategy faces the rigor of prospective clinical testing.

Nevertheless, the conceptual contribution of the work may prove as important as any single result. It challenges the field to think beyond dosimetry when designing bone-targeted radiopharmaceuticals, and to treat the bone microenvironment not as passive scenery but as an active, modifiable participant in treatment response. If radiation can inadvertently remodel the niche into a metastasis-promoting state, then protecting that niche may be as essential as delivering the dose itself. For patients with lung cancer that has invaded the skeleton, where the disease is incurable and skeletal complications compound an already difficult prognosis, a rational pairing of a bone-seeking radioligand with an osteoclast-blocking antibody offers a genuine path forward, and one that leverages drugs already on pharmacy shelves.

Subject of Research: Combining RANKL inhibition with bone-targeted radioligand therapy for lung cancer bone metastases

Article Title: RANKL inhibition potentiates bone-targeted radioligand therapy in lung cancer metastases: a translational study

Article References: Zhao, R., Deng, Y., Liang, W., Xu, M., Lv, J., Zhang, J., Wang, J., Liang, W., Zhou, C., Yu, P., Li, J., Zhu, L., Kung, H. F., & Wang, X. (2026). RANKL inhibition potentiates bone-targeted radioligand therapy in lung cancer metastases: a translational study. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-09021-0

Image Credits: AI Generated

DOI: 10.1186/s12967-026-09021-0

Keywords: radioligand therapy, lung cancer, bone metastases, RANKL inhibition, lutetium-177, bisphosphonates, osteoclastogenesis, denosumab, bone microenvironment, lipid metabolic reprogramming, FABP4, theranostics