Abstract Background With local recurrence of rectal cancer continuing to decrease, distant recurrence is becoming a major concern, especially for patients with low- and intermediate-risk stage II/III rectal cancer. Therefore, a new treatment strategy is warranted for these patients. This single-arm phase II trial aimed to assess the effect of neoadjuvant chemotherapy (NCT) in low- and intermediate-risk stage II/III rectal cancer and explore candidate radiological and clinical parameters for early prediction of tumour response after two cycles of CAPOX. Methods Patients with mid–low stage II/III rectal cancer with low and intermediate risk were examined. The primary outcome was defined as a clinicopathological response by integrating tumour longitudinal length reduction (TLLR) on MRI into pathological tumour regression grade (TRG). After completing NCT, patients with TRG0–2 and TRG3 with a TLLR rate greater than 30 per cent were considered to be responders. Secondary outcomes included pathological complete response (pCR), adverse events and local and distant recurrence. Results This study enrolled 61 eligible patients. No patient was converted to neoadjuvant chemoradiotherapy owing to tumour progression. The clinicopathological response and pCR rates were 78.7 and 21.3 per cent respectively. After two cycles of CAPOX, TLLR, TRG on MRI, and mucosal lesion regression grade on endoscopy had potential discriminative ability (area under the curve greater than 0.7) for predicting both clinicopathological and pathological response. Conclusion NCT alone achieves good tumour response rates in patients with low- and intermediate-risk stage II/III rectal cancer, and predicting tumour response to NCT is feasible at an early treatment phase. Registration number NCT03666442 (http://www.clinicaltrials.gov).

中文翻译：

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低风险和中风险直肠癌单独前期新辅助化疗 (CAPOX) 的早期反应：单组 II 期试验

摘要 背景随着直肠癌局部复发的持续减少，远处复发正成为一个主要问题，特别是对于低风险和中风险 II/III 期直肠癌患者。因此，对于这些患者需要一种新的治疗策略。这项单臂 II 期试验旨在评估新辅助化疗 (NCT) 对低风险和中风险 II/III 期直肠癌的效果，并探索用于早期预测两个周期 CAPOX 后肿瘤反应的候选放射学和临床参数。 方法对具有低风险和中风险的中低II/III期直肠癌患者进行了检查。主要结局被定义为通过将 MRI 上的肿瘤纵向长度减少 (TLLR) 整合到病理肿瘤消退等级 (TRG) 中的临床病理学反应。完成 NCT 后，TLLR 率大于 30% 的 TRG0-2 和 TRG3 患者被视为有反应者。次要结局包括病理完全缓解（pCR）、不良事件以及局部和远处复发。 结果这项研究招募了 61 名符合条件的患者。没有患者因肿瘤进展而转为新辅助放化疗。临床病理学缓解率和 pCR 率分别为 78.7% 和 21.3%。CAPOX 两个周期后，MRI 上的 TLLR、TRG 以及内窥镜检查上的粘膜病变消退等级对于预测临床病理和病理反应具有潜在的判别能力（曲线下面积大于 0.7）。 结论单独使用 NCT 在低风险和中风险 II/III 期直肠癌患者中取得了良好的肿瘤反应率，并且在早期治疗阶段预测 NCT 的肿瘤反应是可行的。 注册号码NCT03666442 (http://www.clinicaltrials.gov)。