由于术后并发症和生活质量 (QOL) 下降，直肠癌的治疗面临着挑战。最近的证据支持对术前治疗后临床完全缓解 (cCR) 的患者采取观察等待 (WW) 方法。在本报告中，我们讨论了一个使用派姆单抗成功治疗错配修复缺陷 (dMMR) 的转移性直肠癌病例。一名 47 岁男性，患有 dMMR 直肠癌和单肝转移，接受了派姆单抗作为新辅助治疗。 10个疗程后，直肠病变达到cCR，促使选择WW入路。肝转移灶明显缩小；然而，怀疑存在残留肿瘤，因此进行了转移切除术。通过组织学检查证实病理完全缓解（pCR）。在24个月的随访中，没有发现肿瘤再生、局部复发或远处转移的证据。对于术前治疗后达到cCR的患者，WW策略越来越被接受。尽管已经记录了接受免疫检查点抑制剂 (ICIs) 治疗的 dMMR 直肠癌患者的 pCR，但通过影像学准确预测 pCR 仍然具有挑战性。该病例说明，整合 ICI 治疗、手术干预和 WW 方法可以有效实现 dMMR 转移性直肠癌治疗的肿瘤学安全性和改善生活质量。© 2024。作者。

Treating rectal cancer presents challenges due to postoperative complications and reduced quality of life (QOL). Recent evidence supports the watch-and-wait (WW) approach for patients with a clinical complete response (cCR) following preoperative treatment. In this report, we discuss a case of metastatic rectal cancer with deficient mismatch repair (dMMR) treated successfully with pembrolizumab.A 47-year-old male with dMMR rectal cancer and a single liver metastasis underwent treatment with pembrolizumab as neoadjuvant therapy. After 10 courses, the rectal lesion achieved cCR, prompting the selection of the WW approach. The liver metastasis showed significant shrinkage; however, the presence of a residual tumor was suspected, leading to a metastasectomy. A pathological complete response (pCR) was confirmed via histological examination. During a 24-month follow-up, there was no evidence of tumor regrowth, local recurrence, or distant metastasis.The WW strategy is increasingly accepted for patients achieving cCR after preoperative treatment. While pCR in dMMR rectal cancer patients treated with immune checkpoint inhibitors (ICIs) has been documented, accurately predicting pCR from imaging remains challenging. This case illustrates that integrating ICI therapy, surgical interventions, and the WW approach can effectively achieve both oncological safety and improved QOL in the treatment of dMMR metastatic rectal cancer.© 2024. The Author(s).