Chemoradiation increases the eligibility for sphincter preservation in low rectal cancer, as assessed by MRI. INTRODUCTION We evaluated whether MRI can predict sphincter preservation after chemoradiation (CRT), and whether the feasibility of sphincter preservation increases after CRT, when compared with MRI before neoadjuvant treatment. METHODS 85 patients with low rectal tumour (≤5 cm from anorectal junction (ARJ)) were included. Radiologist and a surgeon measured the tumour distance to ARJ, and assigned confidence level scores (CLS) for the feasibility of sphincter preserving surgery on MRI. Reference standard was the type of surgery, sphincter preserving vs. non-preserving. RESULTS Tumour distance from the ARJ increased after CRT by 9 mm (p < 0.001). Eligibility for sphincter preservation increased by 21% for the radiologist and 25% for the surgeon, based on CLS. Cut-off for distance to the ARJ after CRT was 28 mm, aiming for optimal specificity. Diagnostic performance after CRT based on CLS yielded an AUC of 0.81 [95%CI 0.70-0.91] for the radiologist and 0.82 [95%CI 0.72-0.92] for the surgeon (p = 0.78). AUCs for tumour distance to the ARJ were 0.85 [95%CI 0.77-0.94] and 0.84 [95%CI 0.75-0.94], respectively (p = 0.84). Interobserver agreement for CLS was moderate before CRT (Κ 0.51; 95%CI 0.36-0.66) and after (K 0.54; 95%CI 0.39-0.69). Measurement of tumour distance to ARJ showed good agreement before (ICC 0.76; 95%CI 0.65-0.84) and after CRT (ICC 0.77; 95%CI 0.66-0.84). CONCLUSION MRI can be a valuable adjunct in the decision making for sphincter preservation after CRT, with distance from the tumour to the ARJ as an accurate and reliable factor. CRT increases the tumour distance to the ARJ, leading to an estimated increase of sphincter preserving surgery in up to 21-25% of patients.

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MRI 预测低位直肠癌 CRT 后保留括约肌的资格增加

根据 MRI 评估，放化疗增加了低位直肠癌保留括约肌的资格。引言 我们评估了 MRI 是否可以预测放化疗 (CRT) 后括约肌的保留，以及与新辅助治疗前的 MRI 相比，CRT 后括约肌保留的可行性是否增加。方法 85 例低位直肠肿瘤患者（距肛门直肠交界处（ARJ）≤5 cm）。放射科医生和外科医生测量了肿瘤与 ARJ 的距离，并为 MRI 保留括约肌手术的可行性分配了置信水平评分 (CLS)。参考标准是手术类型，括约肌保留与非保留。结果 CRT 后，肿瘤与 ARJ 的距离增加了 9 毫米（p < 0.001）。根据 CLS，放射科医师和外科医生的括约肌保留资格分别增加了 21% 和 25%。CRT 后到 ARJ 距离的截止值为 28 mm，旨在获得最佳特异性。基于 CLS 的 CRT 后诊断性能为放射科医师和外科医生提供 0.81 [95%CI 0.70-0.91] 和 0.82 [95%CI 0.72-0.92] 的 AUC（p = 0.78）。肿瘤与 ARJ 距离的 AUC 分别为 0.85 [95%CI 0.77-0.94] 和 0.84 [95%CI 0.75-0.94] (p = 0.84)。CRT 之前（Κ 0.51；95%CI 0.36-0.66）和之后（K 0.54；95%CI 0.39-0.69）的 CLS 观察者间一致性中等。在 CRT 之前 (ICC 0.76; 95%CI 0.65-0.84) 和之后 (ICC 0.77; 95%CI 0.66-0.84) 测量肿瘤到 ARJ 的距离显示出良好的一致性。结论 MRI 可以作为 CRT 后括约肌保留决策的重要辅助手段，将肿瘤到 ARJ 的距离作为准确可靠的因素。CRT 增加了肿瘤与 ARJ 的距离，导致大约 21-25% 的患者接受括约肌保留手术的增加。