Neoadjuvant anti-PD-1 monotherapy followed by watch-and-wait strategy in dMMR/MSI-H colorectal cancer: a multicenter real-world study.

Authors

Tengyu Li, Huaju Zhang, Pengyu Wei, Weiyu Feng, Huiliang Zhang, Shuai Ma, Quanbo Zhou, Shuang Zhao, Luyao Shao, Haifeng Sun, Weipeng Sun, Chao Yang, Shengyun Hu, Qingqing Zhang, Xiaofei Duan, Wei Zhang, Yangbang Lian, Chang Su, Xuexiu Zhang, Zhen Li, Guixian Wang, Weitang Yuan, Zhiyong Zhang, Xuan Zhang, Hongwei Yao, Yugui Lian

Published in

Frontiers in immunology. Volume 17. Pages 1899625. Epub Aug 03, 2026.

Abstract

This study aimed to assess the long-term results of the watch-and-wait (W&W) strategy in patients with clinical stage II/III mismatch repair deficiency (dMMR) or microsatellite instability-high (MSI-H) colorectal cancer (CRC) who received neoadjuvant anti-PD-1 monotherapy.
This retrospective study enrolled stage II/III dMMR/MSI-H CRC patients from four Chinese tertiary hospitals between August 1, 2020 and February 28, 2025. All participants received neoadjuvant anti-PD-1 monotherapy followed by W&W approach. post hoc, endoscopic complete response (eCR) was defined as no suspicious mucosal lesion on white-light or chromoendoscopy (flat scar or normal mucosa allowed) and negative targeted biopsies from the primary tumor site. The primary outcomes were disease-free survival (DFS) and overall survival (OS). The study is registered in the Chinese Clinical Trial Registry (www.chictr.org.cn ChiCTR2500100474).
A total of 49 patients managed with W&W strategy were enrolled, and all met the post hoc eCR criteria. Radiological evaluation showed clinical complete response in 21 patients (44%), partial response in 17 (35%) and stable disease in 10 (21%). One patient lacked evaluable imaging. Median neoadjuvant treatment duration was 6 months (IQR 4-8), with a median of 12 treatment cycles (IQR 8-16). Treatment-related adverse events were grade 1-2 in 14 patients (29%); no grade 3-4 events occurred. At a median follow-up of 35 months (range 9-60), no local regrowth, distant metastasis, or death was recorded. The estimated 3-year DFS and OS are both 100%.
In this cohort, patients with dMMR/MSI-H CRC who met eCR after neoadjuvant anti-PD-1 monotherapy had excellent long-term outcomes when managed with W&W strategy. These findings support the potential utility of endoscopic assessment for selecting candidates for organ preservation, but prospective validation of standardized criteria is warranted.

PMID:
42609473
Bibliographic data and abstract were imported from PubMed on 18 Aug 2026.

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