The study focused on a group that has received comparatively little attention in the immunotherapy era: patients who achieved a non-pathological complete response, abbreviated non-pCR, after receiving neoadjuvant immunochemotherapy, or NICT. This treatment strategy combines chemotherapy with immune checkpoint inhibitors, drugs that unleash the body’s own T cells against cancer by blocking inhibitory receptors such as PD-1. When NICT works spectacularly, the entire tumor is eradicated before surgery, a state called pathological complete response, and these patients enjoy excellent long-term outcomes. But when cancer cells persist in the resected specimen, the prognosis becomes far less certain, and clinicians have lacked clear guidance on how to stratify risk within this heterogeneous population.

To address that gap, the research team led by Hao He, Pengqiang Gao, and Junpeng Lin, with Shuoyan Liu and Feng Wang as corresponding authors, retrospectively analyzed 178 patients with thoracic esophageal squamous cell carcinoma who underwent R0 esophagectomy, meaning a complete surgical resection with clear margins, between January 2020 and December 2023 after receiving NICT. All patients had residual disease on final pathology. The investigators divided them into two groups based on tumor regression grade, a standardized pathological scoring system that quantifies how much of the original tumor was destroyed by preoperative therapy. The TRGa group comprised 84 patients with residual tumor occupying between zero and fifty percent of the original tumor bed, while the TRGb group comprised 94 patients in whom more than half of the tumor remained viable.

The pathological differences between these two groups were striking. Patients in the TRGb group, whose tumors had responded poorly to the preoperative immunochemotherapy, carried far more aggressive biological features at the time of surgery. Deep tumor invasion into the esophageal wall, classified as ypT3-4 stage, was present in 77.7 percent of TRGb patients compared with just 26.2 percent of TRGa patients, a difference that was highly statistically significant. Perineural invasion, in which cancer cells wrap around nerve fibers and gain a conduit for spread, occurred in 44.7 percent of the poor responders versus 6.0 percent of the better responders. Lymphovascular invasion, the presence of tumor cells inside lymphatic or blood vessels and a well-known harbinger of metastasis, was documented in 63.8 percent of TRGb patients compared with 27.4 percent of TRGa patients. Each of these comparisons reached a P value below 0.001, indicating that the association is very unlikely to be a statistical fluke.

These pathological differences translated directly into survival outcomes. The TRGb group demonstrated significantly inferior disease-free survival, the length of time after surgery without any evidence of cancer returning, as well as inferior overall survival. In the language of survival analysis, the curves for the two groups diverged in a statistically meaningful way, with P values of 0.038 for disease-free survival and 0.003 for overall survival. What makes this observation clinically important is that both groups had received the same modern immunotherapy-based regimen and both had undergone the same operation, yet the simple measure of how much tumor remained after treatment cleanly separated patients into distinct prognostic categories. Tumor regression grade, in other words, is not merely a descriptive label but a genuine predictor of who will live and who will relapse.

When the researchers dug deeper using multivariate analysis, a statistical technique that adjusts for multiple factors simultaneously to identify independent predictors, one variable stood out above all others: ypN3, defined as the presence of seven or more regional lymph node metastases on post-treatment pathology. Patients whose resected specimens contained this burden of nodal disease faced a substantially elevated risk of death and recurrence, independent of other clinical and pathological characteristics. This finding is notable because it suggests that even in the immunotherapy era, the extent of lymph node involvement after neoadjuvant treatment remains the dominant driver of long-term outcomes, echoing decades of surgical oncology research while confirming that the principle holds when immune checkpoint inhibitors are added to the equation.

The recurrence patterns themselves told an equally compelling story. Across the entire cohort, 63 of the 178 patients, or 35.4 percent, experienced a recurrence of their disease during follow-up. But the geography of that recurrence differed sharply between the response groups. Patients in the TRGb group developed distant metastases, the spread of cancer to distant organs such as the lungs, liver, or bones, at a rate of 23.4 percent, compared with only 11.9 percent among the TRGa patients, a difference that reached statistical significance with a P value of 0.046. Distant metastasis is the most feared pattern of recurrence because it generally precludes curative salvage treatment, so identifying which patients are prone to it is essential for planning surveillance and adjuvant therapy.

Lymph node status after treatment also shaped the pattern of failure in a way that carries direct implications for how surgeons and radiation oncologists think about treatment volumes. Patients who remained lymph node positive after neoadjuvant therapy, designated ypN+, developed extra-regional lymph node metastases, meaning cancer spread to lymph node stations outside the originally involved regional basin, at a rate of 10.5 percent. Among patients who were node negative after treatment, the ypN0 group, that figure was only 1.1 percent, a nearly tenfold difference that was statistically significant at P equals 0.007. This suggests that persistent nodal disease after immunotherapy is not just a marker of burden within the chest but a signal that the cancer has acquired the capacity to seed distant lymphatic territories, a behavior that standard surveillance protocols may not adequately capture.

Taken together, the results of this single-center study offer a practical framework for risk stratification in a population that is growing rapidly as NICT becomes standard of care for locally advanced esophageal squamous cell carcinoma. The authors conclude that postoperative ypN status should be used to guide risk-adapted adjuvant therapy and to intensify surveillance for high-risk patients. In practical terms, a patient who emerges from surgery with heavy residual tumor, perineural or lymphovascular invasion, or extensive nodal involvement, particularly ypN3 disease, may be an appropriate candidate for escalated postoperative treatment strategies or closer imaging follow-up, whereas patients with minimal residual disease and cleared nodes might safely avoid the toxicity of unnecessary intensification.

The study does carry the inherent limitations of its design: it was retrospective, conducted at a single institution, and included patients treated over a four-year window during which immunotherapy practice was still evolving. Prospective validation in multi-institutional cohorts will be needed before these risk categories can be formally embedded in treatment guidelines. Nevertheless, as immune checkpoint inhibitors continue to reshape the preoperative treatment of esophageal cancer worldwide, this real-world evidence provides oncologists with something they have sorely lacked: a data-driven map of what recurrence actually looks like in patients who do not achieve a complete pathological response, and a clear signal that the pathology report after surgery contains some of the most prognostically valuable information a treating team will ever receive.

Subject of Research: Survival and recurrence patterns in non-pathological complete response after neoadjuvant immunochemotherapy for esophageal squamous cell carcinoma

Article Title: Patterns of survival and recurrence in non-pathological complete response to neoadjuvant immunochemotherapy for esophageal squamous cell carcinoma: a real-world single-center study

Article References: He, H., Gao, P., Lin, J., Wang, P., Liu, S., & Wang, F. (2026). Patterns of survival and recurrence in non-pathological complete response to neoadjuvant immunochemotherapy for esophageal squamous cell carcinoma: a real-world single-center study. BMC Cancer. https://doi.org/10.1186/s12885-026-17041-8

Image Credits: AI Generated

DOI: 10.1186/s12885-026-17041-8

Keywords: esophageal squamous cell carcinoma, neoadjuvant immunochemotherapy, immune checkpoint inhibitors, pathological complete response, tumor regression grade, ypN3, disease-free survival, overall survival, recurrence patterns, distant metastasis, prognostic factors, esophagectomy

The research team, led by Qian Xing, Yong Cui, Xiao-Lei Gu and senior author Ying-Shi Sun, set out to do two things. First, they built a radiomics model—a machine learning pipeline that extracts hundreds of quantitative features from medical images, such as texture, intensity patterns and shape descriptors invisible to the human eye—to predict the tumor regression grade of individual liver metastases from gadoxetic acid-enhanced MRI. Gadoxetic acid is a liver-specific contrast agent that is taken up by functioning hepatocytes, allowing radiologists to image metastases with unusual clarity during the hepatobiliary phase of the scan. Second, and arguably more innovatively, they asked whether the heterogeneity of predicted responses across all of a patient’s lesions—some shrinking dramatically while others barely respond—could itself serve as a warning sign for future recurrence.

The study was a single-center retrospective analysis that included 295 liver lesions from 83 patients with colorectal liver metastases, split into a training group of 199 lesions and a validation group of 96 lesions. For each lesion, the researchers drew regions of interest on the latest preoperative MRI and computed radiomic features, ultimately screening down to 25 informative features that fed the predictive model. Rather than using the conventional five-tier TRG scale directly as the training label, the team used tumor residual rate—the percentage of original tumor tissue still alive after chemotherapy—as a continuous measure of response. This choice allowed the model to learn a graded, quantitative relationship between image texture and biological response rather than forcing predictions into coarse categories.

How well did the model perform? The correlation between the radiomics score and the actual tumor residual rate was moderate in both the training and validation groups, with coefficients of determination of 0.360 and 0.440 respectively. In plain terms, the AI could explain roughly a third to nearly half of the variation in how much tumor tissue survived chemotherapy, based purely on the appearance of the lesions on MRI. The authors describe this as modest predictive performance, and they are careful not to overclaim. Radiomics is not yet a substitute for pathology. But the fact that a noninvasive scan can capture a meaningful fraction of treatment response information at all is significant, because it opens the door to assessing response while the patient is still on chemotherapy, when the treatment plan can still be adjusted.

The truly headline-grabbing finding, however, concerns heterogeneity. The researchers defined radiomics-predicted TRG heterogeneity, abbreviated R_H, as the situation in which a single patient harbors both good predicted responses—predicted TRG 1 to 3, corresponding to a predicted tumor residual rate of 50 percent or less—and poor predicted responses—predicted TRG 4 to 5, with a predicted residual rate above 50 percent—across different liver lesions. This is the imaging equivalent of what pathologists have long observed under the microscope: metastases in the same liver do not respond uniformly to the same drugs. Some lesions melt away while others stubbornly persist, and this mosaic of sensitivity reflects the underlying biological diversity of the cancer.

To test whether this imaging-detected mosaic matters clinically, the team tracked local tumor disease-free survival, or LTDFS, a measure of how long patients remain free of locally recurring disease in the liver. Using Kaplan-Meier survival analysis, they compared the 13 patients whose lesions showed heterogeneity (R_H positive) with the 70 patients whose lesions were uniformly predicted to respond (R_H negative). The difference was stark. Patients with heterogeneous predicted responses had a median local tumor disease-free survival of just 3.0 months, while those without heterogeneity enjoyed a median of 10.2 months—a more than threefold difference that reached statistical significance with a p value of 0.002.

The researchers then pushed further, using Cox regression analysis to determine which factors independently predicted LTDFS when considered alongside clinical characteristics. Three variables emerged as independent predictors: the presence of radiomics-predicted TRG heterogeneity (p = 0.012), the best radiomics-predicted response across all lesions, termed R_min (p = 0.020), and whether the patient had undergone intraoperative radiofrequency ablation, a technique that destroys tumors with heat (p = 0.010). The appearance of R_min among the independent predictors is particularly intriguing. It suggests that the single best-responding lesion in a patient’s liver may carry more prognostic weight than the worst one, hinting that a cancer capable of a strong response somewhere may have a fundamentally more favorable biology than one that responds poorly everywhere.

Why should heterogeneity be so ominous? Tumor heterogeneity is one of the central challenges in modern oncology. A cancer that presents a mixed face to chemotherapy is likely to harbor resistant clones that survive treatment and seed recurrence. When those clones are distributed across multiple lesions in the liver, even complete surgical resection of the visible disease may leave behind microscopic resistant cells destined to regrow. Conventional imaging assessments, such as the RECIST criteria that track changes in lesion size, are poorly equipped to capture this biological diversity, because size is a crude proxy for response. A lesion can shrink substantially yet still be packed with viable tumor, while another may be replaced almost entirely by scar tissue. Radiomics, by quantifying internal texture and signal patterns, offers a window into these differences that simple measurements cannot provide.

The study has limitations that the authors and readers should keep in view. It was retrospective and conducted at a single center, so the model will need external validation in independent cohorts before it can inform clinical decisions. The number of patients with heterogeneity was small—13 individuals—which, while sufficient for statistical significance, leaves room for uncertainty around the precise effect size. The predictive performance of the radiomics model itself was modest, meaning that refinement of feature selection, segmentation and modeling approaches will be needed. Nevertheless, the prognostic signal from heterogeneity was strong enough to stand out even with a first-generation model, which bodes well for improved versions.

The broader implications are considerable. If validated prospectively, a radiomics-based assessment of response heterogeneity could be performed on the same gadoxetic acid-enhanced MRI scans that patients already receive before liver surgery, adding no additional imaging burden. Surgeons could use it to decide which lesions merit resection versus ablation, and oncologists could identify patients whose mixed responses warrant intensified systemic therapy or closer surveillance. The study also adds to a growing body of evidence that artificial intelligence can extract clinically meaningful information from images that radiologists cannot see with the naked eye. For patients with colorectal liver metastases—a disease where the liver remains the dominant site of treatment failure and where every month of disease-free survival matters—a smarter read of a routine scan could ultimately help tailor therapy to the true, uneven biology of each person’s cancer.

Subject of Research: Radiomics-based prediction of tumor regression grade heterogeneity on MRI for prognostic assessment in colorectal cancer liver metastases after neoadjuvant chemotherapy

Article Title: Radiomics-predicted TRG heterogeneity based on gadoxetic acid-enhanced MRI and its prognostic value in patients with CRLM after neoadjuvant chemotherapy

Article References: Xing, Q., Cui, Y., Gu, X.-L., Zhu, H.-T., Li, X.-T., & Sun, Y.-S. (2026). Radiomics-predicted TRG heterogeneity based on gadoxetic acid-enhanced MRI and its prognostic value in patients with CRLM after neoadjuvant chemotherapy. BMC Medical Imaging. https://doi.org/10.1186/s12880-026-02879-y

Image Credits: AI Generated

DOI: 10.1186/s12880-026-02879-y

Keywords: radiomics, colorectal cancer, liver metastases, gadoxetic acid MRI, tumor regression grade, heterogeneity, neoadjuvant chemotherapy, machine learning, prognosis, disease-free survival, medical imaging, artificial intelligence

The study, conducted across three academic medical centers — Nanfang Hospital of Southern Medical University, The Sixth Affiliated Hospital of Sun Yat-sen University, and Sun Yat-sen University Cancer Center — collected patients treated between September 2015 and October 2022. All had received chemotherapy or chemotherapy combined with immunotherapy before undergoing gastrectomy. The regimens reflected current standards of care: doublet or triplet combinations of fluoropyrimidine-based and platinum-based chemotherapy, including XELOX, SOX, FOLFOX, and the docetaxel-containing FLOT protocol, with some patients also receiving PD-1 immune checkpoint inhibitors every three weeks. Radiological response was assessed by enhanced computed tomography after two to three cycles using the RECIST 1.1 criteria, and the overall response rate across the cohort reached 48.4 percent.

Of the 488 patients, 80 — or 16.4 percent — achieved a pathological complete response. To ensure the finding was robust, the researchers harmonized tumor regression grading across institutions: because one center used the National Comprehensive Cancer Network classification while the other two applied the American Joint Committee on Cancer 8th edition system, three blinded gastrointestinal pathologists conducted a centralized review of all specimens, resolving discrepancies by panel consensus. The definition was strict — no residual tumor cells anywhere in the resection specimen or in any of the resected lymph nodes. Notably, seven patients who had no residual tumor in the primary lesion still harbored carcinoma in their regional lymph nodes, and all seven fell into the non-pCR group.

The survival signal was dramatic. Patients with pCR had significantly better overall survival and recurrence-free survival than those with residual disease, with neither median overall survival nor median recurrence-free survival reached in the pCR group during follow-up. For non-pCR patients, median overall survival was 62.8 months and median recurrence-free survival was 20.9 months. Recurrence rates diverged just as sharply: only 7.5 percent of pCR patients — six of eighty — relapsed, compared with 40.2 percent of non-pCR patients, or 164 of 408. Across the entire cohort, 170 patients, or 34.8 percent, experienced recurrence after neoadjuvant treatment and surgery.

But the study’s most provocative finding concerns the six pCR patients who did relapse. Every single one of them had received adjuvant therapy after surgery, while none of the seventeen pCR patients who were simply observed after surgery experienced recurrence. The authors are careful not to overinterpret this counterintuitive pattern. They suggest two possible explanations: selection bias, in which clinicians may have reserved adjuvant treatment for patients perceived to be at higher risk, or the development of chemotherapy resistance to the specific adjuvant regimen used. With only six events among eighty patients, the statistical power is limited, and the researchers explicitly caution that this observation should not be read as evidence against adjuvant therapy. Instead, they argue, it underscores the need for better risk stratification to identify the minority of pCR patients harboring residual micrometastatic disease who might genuinely benefit from additional systemic treatment.

The timing and location of relapse told another important story. There was no significant difference between the pCR and non-pCR groups in when or where recurrence occurred, echoing earlier work — including a 2011 cohort study by Fields and colleagues that found 27 percent of pCR gastric cancer patients relapsed within five years. Among all patients with recurrence in the current study, 73.5 percent developed distant metastases, 8.8 percent had local recurrence, and 6.5 percent had both. Of the six relapsed pCR patients, all were male; two developed locoregional recurrence while three developed distant disease involving the peritoneum, distant lymph nodes, or bone, and three of the six died of their recurrence during follow-up.

To predict who might achieve pCR in the first place, the team built a statistical model using logistic regression and a nomogram — a graphical scoring tool that translates patient characteristics into a personalized probability. Multivariate analysis identified radiological response under RECIST 1.1 as a powerful predictor: patients with a complete or partial radiological response had roughly eight times the odds of achieving pCR compared with those with stable or progressive disease. Even more striking, Epstein-Barr virus-encoded RNA positive status carried an odds ratio of 20.65, making EBER positivity the single strongest molecular predictor in the analysis. After excluding variables with too many missing values, the final nomogram incorporated the neoadjuvant treatment regimen and histological type as independent predictors. The model performed well, achieving a concordance index of 0.844 in the training set and 0.820 in the validation set, with calibration curves showing satisfactory agreement between predicted and observed outcomes and decision curve analysis confirming clinical utility.

The immunotherapy question yielded a nuanced answer. Adding immune checkpoint inhibitors to neoadjuvant chemotherapy significantly increased the pCR rate and cut the recurrence rate nearly threefold — 15.1 percent versus 40.3 percent for chemotherapy alone. Yet this did not translate into significantly longer recurrence-free or overall survival, with Kaplan-Meier comparisons showing no statistically significant difference between the two treatment groups. The finding mirrors results from major international trials: the phase III KEYNOTE-585 study demonstrated that pembrolizumab plus chemotherapy significantly raised pCR rates in locally advanced gastric and gastroesophageal junction cancer but failed to significantly improve event-free survival, while the DANTE trial reported promising pathological responses with atezolizumab-based perioperative therapy. The disconnect between pathological response and hard survival endpoints remains one of the field’s central puzzles, and the authors call for research integrating circulating tumor DNA, radiomics, and digital pathology to predict long-term outcomes more accurately.

Beyond pCR, the study identified clear risk factors for recurrence in the broader population: patients with five or more positive regional lymph nodes had nearly four times the recurrence risk, those with poorly differentiated tumors and neurovascular invasion were also at elevated risk, and a high lymph node ratio — above 30 percent — predicted significantly shorter overall and recurrence-free survival. Tumor regression grade itself mattered, with a three-year recurrence-free survival of 66.5 percent for patients with the best regression grades compared with 50.9 percent for those with lesser responses. Intriguingly, among patients with the best regression grades, those who skipped postoperative systemic therapy had a numerically higher three-year recurrence-free survival of 81.4 percent versus 64.4 percent, though the difference was not statistically significant.

The study has limitations the authors acknowledge candidly: its retrospective design invites selection and treatment bias, the small number of recurrence events among pCR patients limits statistical power, center heterogeneity introduced variability in practices and data collection, and the nomogram lacks external validation. Missing data on Lauren classification and PD-L1 combined positive scores further constrained the analysis. Still, as the largest sample of gastric and gastroesophageal junction cancer patients with pCR after neoadjuvant treatment and radical surgery to date, the study delivers a clear message for clinicians and patients alike: a pathological complete response is one of the most favorable outcomes in this disease, associated with dramatically lower recurrence and superior survival, but it is not a guarantee of cure. The role of adjuvant therapy for these patients remains unresolved, and the authors argue that only prospective randomized trials can settle whether additional postoperative treatment helps or harms the patients whose tumors have already vanished.

Subject of Research: Pathological complete response and survival after neoadjuvant treatment of locally advanced gastric cancer

Article Title: Characteristics and survival associated with pathological complete response following neoadjuvant treatment of locally advanced gastric cancer: a multicenter analysis in a real-world setting

Article References: Lai, M.-Y., Luo, D.-D., Chen, S., Yan, X., Tan, W.-Y., Guan, W.-L., Zhou, Z.-W., Zhao, L.-Y., & Qiu, M.-Z. (2026). Characteristics and survival associated with pathological complete response following neoadjuvant treatment of locally advanced gastric cancer: a multicenter analysis in a real-world setting. Holistic Integrative Oncology, 5(1), Article 53. https://doi.org/10.1007/s44178-026-00273-w

Image Credits: AI Generated

DOI: 10.1007/s44178-026-00273-w

Keywords: gastric cancer, pathological complete response, neoadjuvant treatment, immunotherapy, chemotherapy, recurrence, overall survival, recurrence-free survival, nomogram, tumor regression grade, gastroesophageal junction cancer, adjuvant therapy

The research, led by Zhuo Han and Nan Wang of Tangdu Hospital at the Fourth Military Medical University together with colleagues from Beijing Chaoyang Hospital and Xijing Hospital, analyzed 154 patients with obstructive colorectal cancer treated between 2011 and 2025. Ninety-three patients received a self-expandable metal stent followed by neoadjuvant therapy, while 61 underwent stent placement alone before surgery. Because treatment practices evolved dramatically over the fourteen-year enrollment window, the investigators stratified their analysis into two eras, 2011 to 2020 and 2021 to 2025, to separate the effects of the combined strategy from the effects of technological progress.

The biological rationale behind the combined approach is rooted in the peculiar hostility of the obstructed bowel. Compared with non-obstructive colorectal cancer, obstructed tumors are more often left-sided, larger, more poorly differentiated, and diagnosed at more advanced stages, with a greater tendency toward peritoneal spread. Obstruction also drives a cascade of systemic problems: elevated inflammatory markers such as C-reactive protein and interleukin-6, hypoproteinemia and malnutrition, and reduced physical activity that accelerates muscle loss and frailty. Recent molecular work has even identified distinct features of the obstructed tumor microenvironment, including altered extracellular matrix stiffness, activated cancer-associated fibroblasts, and a dense infiltration of CD8-positive T cells that paradoxically correlates with worse prognosis.

Emergency surgery for these patients carries perioperative mortality rates as high as 10 to 15 percent, along with elevated risks of anastomotic leakage, wound infection, and permanent stoma formation. Self-expandable metal stents, introduced in the 1990s, offered a minimally invasive alternative: an endoscopist deploys a mesh tube across the tumor, restoring bowel continuity within hours and converting an emergency into an elective operation. Meta-analyses have shown lower early complication rates, lower mortality, and far fewer stomas with stenting compared with emergency surgery. Yet long-term oncological concerns persisted, most notably a prospective study reporting significantly higher local recurrence after stenting, possibly linked to microperforations or mechanical manipulation of the tumor releasing circulating tumor DNA.

The new study addresses those concerns by layering neoadjuvant therapy onto the stent pathway. After decompression, multidisciplinary teams at each center assessed patients for systemic treatment based on locally advanced disease, molecular subtype, resectability, and performance status. Regimens ranged from XELOX and FOLFOX chemotherapy to combinations with cetuximab for RAS and BRAF wild-type left-sided tumors, and immunotherapy for patients with microsatellite instability-high or mismatch repair-deficient tumors. The theory is that decompression first reduces bowel wall edema and peritumoral inflammation, creating a healthier substrate for treatment and surgery, while neoadjuvant drugs shrink the tumor, downstage nodal disease, and potentially eradicate micrometastases.

The short-term surgical results were striking. In the 2011 to 2020 cohort, the stent-plus-therapy group had an intraoperative stoma rate of 8.6 percent versus 29.0 percent for stent alone, and postoperative complications of 8.6 percent versus 29.0 percent, both statistically significant differences. These advantages persisted into the 2021 to 2025 period. The authors attribute this to a synergistic mechanism: stent-induced decompression resolves intestinal wall edema and restores blood supply, converting lesions once deemed unsuitable for safe anastomosis into ones where primary reconstruction is feasible, while neoadjuvant therapy further reduces tumor volume and inflammation. Avoiding a stoma carries profound quality-of-life implications, with longitudinal data showing that ostomy patients suffer persistent deficits in physical, emotional, and social functioning for up to a year after surgery.

Pathological outcomes told an equally compelling story about the modern era. In the 2021 to 2025 cohort, 20.7 percent of neoadjuvant-treated patients achieved major tumor regression, graded as Tumor Regression Grade 0 to 1, and rates of T and N downstaging reached 39.7 percent and 60.3 percent respectively, far exceeding the earlier period when regimens consisted mainly of standard chemotherapy alone. The contemporary group also showed significantly fewer positive lymph nodes and significant improvements in pathological T and N stages. The authors link this enhanced response to the evolution of neoadjuvant regimens, including targeted and immune-based combinations that act on both the primary tumor and micrometastatic disease.

Survival analysis revealed a nuanced picture. In the earlier cohort, the neoadjuvant group showed marginally better three- and five-year disease-free and overall survival, but the differences did not reach statistical significance. In the 2021 to 2025 cohort, however, the combined strategy was associated with a statistically significant improvement in overall survival, with a reported P value of 0.013, while disease-free survival had not yet diverged, possibly because follow-up in that cohort remains short at a median of 41.3 months. The authors caution that retrospective design, modest sample size, and the absence of propensity score matching limit causal inference, but the consistency of surgical and pathological benefits across both eras strengthens the overall signal.

Perhaps the most practice-changing finding concerns timing. For patients treated with a stent alone, an interval of 14 to 21 days between stenting and surgery was associated with significantly better overall survival, a window during which decompression restores nutrition, dampens systemic inflammation, and allows prehabilitation without giving the tumor unnecessary time to progress. For patients receiving neoadjuvant therapy, the calculus differs: intervals exceeding 90 days were associated with significantly worse disease-free survival, suggesting that systemic treatment should be completed and surgery performed within roughly three months. A nationwide Chinese survey cited in the paper found that nearly half of stenting hospitals operated within two weeks, while about a fifth waited ten to twelve weeks when neoadjuvant therapy was given, underscoring how variable current practice remains.

The study arrives as two prospective trials, OUTSTAND and NACSOC-02, work to confirm whether stent-based neoadjuvant strategies can be standardized for obstructive left-sided colorectal cancer, with the latter testing immunotherapy combinations after decompression. For now, the retrospective evidence offers a coherent clinical algorithm: decompress with a stent at an experienced center, use the restored physiological window to deliver modern systemic therapy tailored to molecular subtype, and schedule radical surgery within a defined interval, ideally before 90 days elapse. If prospective data validate these findings, the dreaded obstructed bowel, long a surgical emergency defined by rushed decisions and permanent stomas, may instead become the starting point of a carefully sequenced, multidisciplinary treatment plan that improves both survival and the daily lives of patients.

Subject of Research: Neoadjuvant therapy combined with self-expandable metal stent placement for obstructive colorectal cancer

Article Title: Comparative effectiveness of neoadjuvant therapy combined with stent placement versus stent alone in obstructive colorectal cancer: a multicenter retrospective analysis

Article References: Han, Z., Zhang, B., Liu, S., Wu, T., Qiao, Q., He, X., Han, J., & Wang, N. (2026). Comparative effectiveness of neoadjuvant therapy combined with stent placement versus stent alone in obstructive colorectal cancer: a multicenter retrospective analysis. BMC Cancer, 26(1), Article 1139. https://doi.org/10.1186/s12885-026-16728-2

Image Credits: AI Generated

DOI: 10.1186/s12885-026-16728-2

Keywords: colorectal cancer, bowel obstruction, self-expandable metal stent, neoadjuvant therapy, bridge to surgery, overall survival, disease-free survival, tumor regression grade, surgical timing, stoma, immunotherapy, retrospective study

The research, led by Xiaoyan Li, Chunning Li and colleagues at the Cancer Hospital of China Medical University and Liaoning Cancer Hospital & Institute in Shenyang, began with an unbiased search for molecular features that distinguish tumors resistant to chemoimmunotherapy from those that shrink dramatically under treatment. Rather than examining genes in isolation, the team integrated two complementary high-resolution technologies. The first was proteomic profiling using liquid chromatography with tandem mass spectrometry, applied to clinical esophageal cancer specimens from eight patients, which allowed the researchers to catalogue thousands of proteins actually present inside the tumors. The second was single-cell RNA sequencing, performed on three esophageal tumors and one normal esophageal tissue sample, which provided a cell-by-cell map of gene expression across the entire tumor ecosystem, from malignant epithelial cells to stromal fibroblasts and infiltrating immune cells.

Converging evidence from these two approaches converged on a single molecule. CYP2S1, a member of the cytochrome P450 superfamily of enzymes best known for their roles in metabolizing fatty acids, drugs and other small molecules, stood out as significantly upregulated in tumors that had resisted chemoimmunotherapy. The single-cell data added a crucial layer of context: the enzyme was not produced uniformly throughout the tumor but was predominantly expressed by the malignant epithelial cells themselves. This tumor-intrinsic pattern of expression was important, because it suggested that the cancer cells were not merely passive victims of an unfavorable immune environment but were actively manufacturing a molecule associated with immune exclusion and treatment failure.

To move from correlation to biological plausibility, the investigators turned their attention to the tumor microenvironment, the complex ecosystem of immune and stromal cells that surrounds and infiltrates a tumor. Using immunohistochemistry, a technique that stains tissue sections to reveal the location and abundance of specific proteins, and multiplex immunofluorescence, which can visualize several protein markers simultaneously in the same tissue section, the team examined tumor samples at single-cell resolution. Their analyses revealed that tumors with high CYP2S1 expression contained markedly increased numbers of cells with the phenotypic characteristics of polymorphonuclear myeloid-derived suppressor cells, or PMN-MDSCs. These cells, which are related to neutrophils, are among the most potent immunosuppressive players in cancer biology. They accumulate in tumors under chronic inflammatory conditions and suppress the activity of cytotoxic T lymphocytes, the very cells that immune checkpoint inhibitors are designed to unleash against the cancer.

The clinical significance of this finding became apparent when the researchers examined the relationship between CYP2S1 protein levels and treatment response in a cohort of 46 evaluable patients who had undergone neoadjuvant chemoimmunotherapy. Response was assessed using the Mandard tumor regression grade, a pathological scoring system that pathologists use to quantify how much residual tumor remains after preoperative treatment, with lower grades indicating more complete tumor destruction. The results were striking: the CYP2S1 immunohistochemical score was positively associated with the tumor regression grade, meaning that patients whose tumors expressed more CYP2S1 tended to have less tumor regression and thus a poorer response to therapy. The statistical relationship was robust, with a linear regression analysis yielding an R-squared value of 0.271 and a P value of 0.0002, while a Spearman correlation coefficient of 0.528 with a P value below 0.001 confirmed the strength of the association.

With a firm clinical correlation established, the team turned to laboratory experiments to dissect the mechanism. Using short hairpin RNA and small interfering RNA techniques to reduce CYP2S1 expression in esophageal cancer cell lines, they observed that silencing the enzyme lowered intracellular levels of reactive oxygen species, the chemically reactive molecules containing oxygen that accumulate in stressed cells, and simultaneously reduced the expression of several chemokines known to attract myeloid cells. Conversely, when the researchers forced tumor cells to overproduce CYP2S1, reactive oxygen species accumulated and the cells secreted elevated amounts of two chemokines in particular: CXCL6 and CXCL8. Both of these signaling molecules belong to the CXC chemokine family and are well documented as chemoattractants for neutrophils and neutrophil-like suppressor cells, providing a plausible route by which tumor cell CYP2S1 could recruit PMN-MDSCs into the tumor bed.

To confirm that the chemokine induction was genuinely dependent on reactive oxygen species rather than some parallel effect of CYP2S1, the investigators performed a scavenging experiment using N-acetylcysteine, a well-established antioxidant that neutralizes intracellular reactive oxygen species. When cells overexpressing CYP2S1 were treated with N-acetylcysteine, the accumulation of reactive oxygen species was attenuated, the induction of CXCL6 and CXCL8 messenger RNA was reduced, and the secretion of CXCL8 protein declined. These results support a model in which CYP2S1 drives a reactive-oxygen-species-dependent signaling program that culminates in the production of myeloid-attracting chemokines. In this framework, the enzyme acts as a molecular switch inside malignant cells, converting metabolic and oxidative activity into an inflammatory signal that reshapes the immune composition of the surrounding tumor.

The broader implications of this work extend beyond esophageal squamous cell carcinoma. Cytochrome P450 enzymes have long interested cancer researchers because of their roles in drug metabolism and in the synthesis of signaling lipids, but CYP2S1 has remained comparatively understudied in the context of tumor immunology. By linking this enzyme to the reactive oxygen species, CXCL6 and CXCL8 axis and to the accumulation of immunosuppressive myeloid cells, the study adds a new node to the growing network of tumor-intrinsic mechanisms of immune evasion. It also offers a potential explanation for why some tumors with similar PD-L1 expression levels respond so differently to checkpoint inhibitors: the determinant of sensitivity may lie not in the checkpoint pathway itself but in whether the tumor has built a chemical wall of suppressive myeloid cells that antibodies cannot penetrate.

Translational possibilities follow naturally from these findings. If CYP2S1 expression in pretreatment biopsy samples proves predictive in larger cohorts, it could serve as a biomarker to identify patients unlikely to benefit from neoadjuvant chemoimmunotherapy, sparing them the toxicity of an ineffective regimen and directing them toward alternative strategies. More ambitiously, the CYP2S1–reactive oxygen species–CXCL6/CXCL8 pathway itself presents multiple candidate points of therapeutic intervention, from inhibiting the enzyme or its oxidative products to blocking the chemokine receptors that guide PMN-MDSCs into tumors. Such approaches would need careful validation, since reactive oxygen species play complex and sometimes protective roles in normal tissue biology, and myeloid cell biology differs substantially between mice and humans.

The study also carries methodological lessons for the field. By combining unbiased proteomics, single-cell transcriptomics, multiplex tissue imaging, patient-level pathological correlations and mechanistic cell biology within a single investigation, the researchers demonstrated how multi-omics integration can move a candidate biomarker from discovery to biological explanation in one continuous chain of evidence. The work adhered to the principles of the Declaration of Helsinki, received approval from the Ethics Committee of the Cancer Hospital of China Medical University, and all patients provided written informed consent. As chemoimmunotherapy becomes standard of care for more cancers and more patients, understanding why it fails will be as important as celebrating why it works. This study suggests that sometimes the answer lies in a quiet metabolic enzyme, humming away inside the tumor cell, quietly sending out the molecular invitations that summon the very cells that shield the cancer from destruction.

Subject of Research: CYP2S1-mediated recruitment of polymorphonuclear myeloid-derived suppressor cells and chemoimmunotherapy resistance in esophageal squamous cell carcinoma

Article Title: CYP2S1: a novel regulator of PMN-MDSC recruitment and immunotherapy resistance in esophageal squamous cell carcinoma

Article References: CYP2S1: a novel regulator of PMN-MDSC recruitment and immunotherapy resistance in esophageal squamous cell carcinoma. (n.d.). https://doi.org/10.1007/s00262-026-04556-z

Image Credits: AI Generated

DOI: 10.1007/s00262-026-04556-z

Keywords: CYP2S1, esophageal squamous cell carcinoma, immunotherapy resistance, PMN-MDSC, tumor microenvironment, reactive oxygen species, CXCL6, CXCL8, chemoimmunotherapy, tumor regression grade, single-cell RNA sequencing, cancer immunology