From the Colorectal Cancer Center, Department of General Surgery (Y.S., W.M., M.W., M.Q., Z.W.), and Department of Radiology (X.G., H.Z.), West China Hospital, Sichuan University, No. 37 Guo Xue Xiang St, Chengdu 86610000, China; and Department of Epidemiology and Medical Statistics, West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, China (Y.H.).
Radiology. 2024 Aug;312(2):e232908. doi: 10.1148/radiol.232908.
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 See also the editorial by Santiago and Shur in this issue.
背景 新辅助化疗（NCT）越来越多地被用于治疗无不良预后因素的局部晚期直肠癌（LARC）患者。然而，MRI 在评估 NCT 后肿瘤反应方面的价值仍不清楚。目的 研究在未接受放疗的接受 NCT 后手术的 LARC 患者中，MRI 评估病理完全缓解的准确性。材料与方法 对两项连续前瞻性临床试验中的影像学亚研究进行了回顾性分析：扩展二期试验（2017 年 12 月至 2021 年 5 月）和 COPEC 试验（比较单独接受两周期或四周期新辅助化疗的肿瘤反应，正在进行中）从 2021 年 8 月）。所有纳入的参与者在手术前均接受了卡培他滨联合奥沙利铂（或 CAPOX）的四个周期治疗。三位放射科医生对肿瘤反应进行了独立评估，使用了五种方法，即单独的磁共振肿瘤消退分级（MR-TRG）、弥散加权成像（DWI）、DWI 改良的 MR-TRG（DWImodMR-TRG）、MRI 完全缓解和放射学新辅助反应评分。以病理评估为参考标准，确定这些模型的阳性和阴性预测值、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 检验比较模型的 AUC。结果 共纳入 224 名参与者，其中扩展二期试验 119 名（中位年龄 61 岁[IQR，53-67]；89 名男性），COPEC 试验 105 名（中位年龄 59 岁[IQR，53-67]；65 名男性）。MR-TRG、DWI、DWImodMR-TRG、MRI 完全缓解和放射学新辅助反应评分与病理完全缓解相关。DWImodMR-TRG 的 AUC 最高，为 0.90（95%CI：0.85，0.95），特异性为 89%（162/182），阴性预测值为 93%（162/174）。结论 MRI 模型在预测 NCT 后 LARC 患者的病理完全缓解方面具有较高的准确性。DWI 提高了 MRI 评估的预测性能。© RSNA，2024 参见本期 Santiago 和 Shur 的社论。
