Mucinous Response Following Preoperative Bevacizumab, Capecitabine, Oxaliplatin, and Radiation is a Diagnostic Pitfall in Assessment of Tumor Type, Regression Grade, and Stage in Patients With Locally Advanced Low Rectal Cancer
Bibliographic record
Abstract
Locally advanced colorectal adenocarcinomas are commonly treated with preoperative chemoradiotherapy (CRT). Neoadjuvant CRT may downstage patients, induce tumor regression, and pathological complete response (pCR). With a variety of histologic patterns of tumor response, accurate pathologic staging can be challenging. The aim of this study was to evaluate the pathologic response to CRT, identify diagnostic pitfalls, and determine whether the expression of the excision repair cross-complementing 1 (ERCC1) and thymidylate synthase (TS) can predict clinical outcome in patients with locally advanced low rectal cancer treated with preoperative CRT. Forty-two patients were enrolled in a phase II trial of preoperative bevacizumab, capecitabine, oxaliplatin, and radiation. Slides and tumor blocks from 38 of these patients who went onto definitive surgery were retrieved from referring hospitals and a central review of slides was performed. Tumor regression grade was calculated, histologic patterns of tumor response, and reasons for changes to pathological stage on central pathology review were analyzed. pCR was seen in 23.6% (9/38) of patients. Central review resulted in change in pathological stage rendered previously in 15.8% (6/38) of cases, with two patients being upstaged, and 4 downstaged. All cases following CRT showed some degree of necrosis and fibrosis. Acellular mucin pools (15.8%, 6/38) and mucin pools surrounded by neoplastic glands (23.6%, 9/38) were identified as common reasons for changes to pathological stage. Furthermore, these two histologic findings resulted in reclassification of tumor subtype as mucin pools surrounded by adenomatous glands were misinterpreted as mucinous adenocarcinoma (7.89%, 3/38). ERCC1 and TS immunohistochemical expression data are being accumulated and will be presented at the meeting. Histologic responses to preoperative CRT present challenges to diagnostic surgical pathologists. To render accurate diagnoses, stage, and valuable prognostic information, resected specimens showing mucin pools should be interpreted with caution.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".