新辅助化疗和放疗（CRT）治疗的部分反应主要表现为收缩或破裂两种模式。本研究旨在探讨这些反应模式在直肠癌中的相关性，与其他反应指标的相关性，以及预后。研究包括197例测试组和218例验证组，均为经CRT治疗的直肠腺癌患者，均为部分反应。两位独立观察者使用先前开发的三步流程图对反应模式进行评分。肿瘤远端回归分级（TRG）根据美国病理学家学会（CAP）和Dworak分类确定。在两个组中，主要的反应模式是破裂（分别为70%和74%），评分观察者间一致性良好（k=0.85）。破裂模式患者的病理分期较高（ypTNM II-IV，78%对35%，P<0.001），Dworak（P=0.004）和CAP TRG（P=0.005）的肿瘤回归较少，与收缩模式患者相比。作为预后的预测指标，收缩模式优于TRG分类，在总体生存（破裂模式，风险比[HR]2.04，95%置信区间[CI]1.19-3.50，P=0.008）和无疾病生存（DFS；破裂模式，HR 2.50，95% CI1.23-5.10，P=0.011）上更好地对患者进行分层。多变量回归分析显示病理分期是DFS的唯一独立预测因子。CRT后肿瘤反应的异质性反映在破裂和收缩模式中。在直肠癌中，破裂模式较为普遍，与晚期和较少肿瘤回归相关。尽管与生存率无关，这些可重现的模式有助于了解肿瘤反应的生物学特性。©2023作者。由约翰威立出版社出版的组织病理学。

Partial response to neoadjuvant chemoradiotherapy (CRT) presents with one of two main response patterns: shrinkage or fragmentation. This study investigated the relevance of these response patterns in rectal cancer, correlation with other response indicators, and outcome.The study included a test (n = 197) and a validation cohort (n = 218) of post-CRT patients with rectal adenocarcinoma not otherwise specified and a partial response. Response patterns were scored by two independent observers using a previously developed three-step flowchart. Tumour regression grading (TRG) was established according to both the College of American Pathologists (CAP) and Dworak classifications. In both cohorts, the predominant response pattern was fragmentation (70% and 74%), and the scoring interobserver agreement was excellent (k = 0.85). Patients with a fragmented pattern presented with significantly higher pathological stage (ypTNM II-IV, 78% versus 35%; P < 0.001), less tumour regression with Dworak (P = 0.004), and CAP TRG (P = 0.005) compared to patients with a shrinkage pattern. As a predictor of prognosis, the shrinkage pattern outperformed the TRG classification and stratified patients better in overall (fragmented pattern, hazard ratio [HR] 2.04, 95% confidence interval [CI] 1.19-3.50, P = 0.008) and disease-free survival (DFS; fragmented pattern, HR 2.50, 95% CI 1.23-5.10, P = 0.011) in the combined cohorts. The multivariable regression analyses revealed pathological stage as the only independent predictor of DFS.The heterogeneous nature of tumour response following CRT is reflected in fragmentation and shrinkage. In rectal cancer there is a predominance of the fragmented pattern, which is associated with advanced stage and less tumour regression. While not independently associated with survival, these reproducible patterns give insights into the biology of tumour response.© 2023 The Authors. Histopathology published by John Wiley & Sons Ltd.