[Short-term efficacy and safety of neoadjuvant immunotherapy for locally advanced colon cancer with deficient mismatch repair].

Objective: To investigate the short-term efficacy and safety of neoadjuvant immunotherapy in patients with locally advanced colon cancer with deficient mismatch repair (dMMR) or microsatellite instability-high (MSI-H). Methods: A retrospective analysis was conducted on the clinicopathological data of 21 patients with dMMR/MSI-H locally advanced colon cancer who received neoadjuvant immunotherapy followed by radical resection at the Cancer Hospital, Chinese Academy of Medical Sciences between February 2023 and December 2025.

The short-term efficacy and safety of neoadjuvant immunotherapy and subsequent radical surgery were evaluated. Results: Among the 21 patients, there were 15 male and 6 female, with a median age of 54 years (range, 33 to 79 years). Ten patients had ascending colon cancer, six had sigmoid colon cancer, four had transverse colon cancer, and one had descending colon cancer. No grade 4 or higher immune-related adverse events (irAEs) occurred in any patient after neoadjuvant immunotherapy. Grade 1 to 2 irAEs were occurred in 8 patients (38.1%, 8/21), and only 1 patient (4.8%, 1/21) developed grade 3 irAE.

All patients underwent radical surgery after neoadjuvant immunotherapy, with R0 resection rate of 100.0% (21/21). No patient developed grade Ⅲ or higher postoperative complications. Only four patients (19.0%, 4/21) develpoed grade Ⅰ to Ⅱ postoperative complications, including anastomotic leakage in one patient (4.8%, 1/21), paralytic intestinal obstruction in 1 patient (4.8%, 1/21), intra-abdominal infection in 1 patient (4.8%, 1/21), and fever in 1 patient (4.8%, 1/21). Postoperative pathological results showed that all patients achieved tumor downstaging compared with the clinical stage before neoadjuvant therapy.

Sixteen patients (76.2%, 16/21) achieved pathological complete response (pCR), and 18 patients (85.7%, 18/21) achieved major pathological response (MPR).

With a median follow-up of 12 months (range, 3 to 37 months), no patient developed local recurrence or distant metastasis. Conclusion: For patients with dMMR/MSI-H locally advanced colon cancer, preoperative neoadjuvant immunotherapy can achieve remarkable efficacy without increasing the risk of postoperative complications, representing a safe and effective therapeutic strategy. 目的： 探讨错配修复缺陷（dMMR）或微卫星高度不稳定（MSI-H）局部进展期结肠癌患者术前接受新辅助免疫治疗的近期疗效及安全性。 方法： 回顾性收集2023年2月至2025年12月在中国医学科学院肿瘤医院接受新辅助免疫治疗后行根治性手术的21例dMMR/MSI-H型局部进展期结肠癌患者的临床病理资料。分析患者接受新辅助免疫治疗及根治性手术的近期疗效和安全性。 结果： 21例患者中，男15例，女6例；中位年龄为54岁（年龄范围33～79岁）；升结肠癌10例，乙状结肠癌6例，横结肠癌4例，降结肠癌1例。全组患者接受新辅助免疫治疗后均未发生4级及以上免疫治疗相关不良事件，8例（38.1%，8/21）患者发生了1～2级免疫治疗相关不良反应，仅1例（4.8%，1/21）患者发生3级免疫治疗相关不良反应。所有患者在新辅助免疫治疗后均接受了根治性手术，R0切除率为100.0%（21/21）。全组患者术后均未发生Ⅲ级及以上并发症，仅4例（19.0%，4/21）患者发生Ⅰ～Ⅱ级术后并发症，分别为吻合口瘘1例（4.8%，1/21）、麻痹性肠梗阻1例（4.8%，1/21）、腹腔感染1例（4.8%，1/21）和发热1例（4.8%，1/21）。术后病理结果显示，所有患者肿瘤病理分期较新辅助治疗前临床分期均实现降期。16例（76.2%，16/21）患者达到病理完全缓解，18例（85.7%，18/21）患者达到主要病理缓解。中位随访12个月（随访时间为3～37个月），全组患者均未出现局部复发或远处转移。 结论： 对于dMMR/MSI-H局部进展期结肠癌患者，术前接受新辅助免疫治疗可取得显著疗效，且不增加术后并发症发生风险，是一种安全且有效的治疗模式。.