Background Neoadjuvant chemotherapy (NCT) is gaining acceptance for the management of locally advanced rectal cancer (LARC) in patients without negative prognostic factors. However, the value of MRI in evaluating tumor response after NCT remains unclear. Purpose To investigate the accuracy of MRI in assessing pathologic complete response in participants with LARC who underwent surgery after NCT without radiation. Materials and Methods A retrospective imaging substudy was conducted within two consecutive prospective clinical trials: the expanded phase II trial (from December 2017 to May 2021) and the COPEC trial (comparison of tumor response to two or four cycles of neoadjuvant chemotherapy alone, ongoing from August 2021). All included participants received four cycles of capecitabine combined with oxaliplatin (or CAPOX) before surgery. Three radiologists who were blinded to the clinicopathologic data independently evaluated the tumor response using five methods, namely, MR tumor regression grade (MR-TRG) alone, diffusion-weighted imaging (DWI) alone, DWI-modified MR-TRG (DWImodMR-TRG), MRI complete response, and radiologic neoadjuvant response score. With pathologic assessment serving as the reference standard, the positive and negative predictive values, sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) were determined to evaluate the accuracy and performance of these models. The AUCs of the models were compared using the DeLong test. Results A total of 224 participants were included, comprising 119 from the expanded phase II trial (median age, 61 years [IQR, 53-67]; 89 male) and 105 from the COPEC trial (median age, 59 years [IQR, 53-67]; 65 male). MR-TRG, DWI, DWImodMR-TRG, MRI complete response, and the radiologic neoadjuvant response score were associated with pathologic complete response. DWImodMR-TRG achieved the highest AUC of 0.90 (95% CI: 0.85, 0.95), with a specificity of 89% (162 of 182) and a negative predictive value of 93% (162 of 174). Conclusion MRI-based models were accurate for determining pathologic complete response in participants with LARC following NCT. DWI improved the predictive performance of MRI-based assessment. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Santiago and Shur in this issue.

中文翻译：

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直肠腺癌对单独新辅助化疗而不放疗的 MRI 肿瘤消退反应。


背景 新辅助化疗 (NCT) 对于治疗没有负面预后因素的局部晚期直肠癌 (LARC) 患者越来越被接受。然而，MRI 在评估 NCT 后肿瘤反应中的价值仍不清楚。目的 探讨 MRI 在评估 NCT 后接受无放射手术的 LARC 参与者的病理完全缓解方面的准确性。材2021 年 8 月）。所有纳入的参与者在手术前均接受了四个周期的卡培他滨联合奥沙利铂（或 CAPOX）治疗。三位对临床病理数据不知情的放射科医生使用五种方法独立评估肿瘤反应，即单独 MR 肿瘤消退等级 (MR-TRG)、单独扩散加权成像 (DWI)、DWI 改良 MR-TRG (DWImodMR-TRG) ）、MRI 完全缓解和放射学新辅助缓解评分。以病理评估作为参考标准，确定阳性和阴性预测值、敏感性、特异性和受试者工作特征曲线下面积（AUC），以评估这些模型的准确性和性能。使用 DeLong 测试比较模型的 AUC。结果 总共纳入 224 名参与者，其中 119 名来自扩大 II 期试验（中位年龄 61 岁 [IQR，53-67]；89 名男性），105 名来自 COPEC 试验（中位年龄 59 岁 [IQR，53]）。 -67]；65 男性）。 MR-TRG、DWI、DWImodMR-TRG、MRI 完全缓解和放射学新辅助缓解评分与病理完全缓解相关。 DWImodMR-TRG 达到最高 AUC 0.90（95% CI：0.85，0.95），特异性为 89%（182 中的 162），阴性预测值为 93%（174 中的 162）。结论 基于 MRI 的模型可准确确定 NCT 后 LARC 参与者的病理完全缓解。 DWI 提高了基于 MRI 的评估的预测性能。 © RSNA，2024 本文提供补充材料。另请参阅本期圣地亚哥和舒尔的社论。