Nicholas Hornstein, Gastrointestinal Medical Oncologist and Assistant Professor at Northwell Health Cancer Institute, shared on X:
“We know immunotherapy works in MSI-H colorectal cancer. The question is, how long do we actually need to treat patients?
Grateful we’re finally getting some answers ahead of ESMO 2026.
A new multicenter study from China published in JITC evaluated 129 patients with dMMR/MSI-H CRC who achieved a clinical complete response to PD-1 inhibition and pursued non-operative management.
66 stopped treatment, while 63 continued maintenance.
At 3 years:
- DFS: 96.2% vs 98.3%
- OS: 100% vs 98.3%
- Only 2 local regrowths, both in the observation group and both successfully salvaged
- No distant metastases
Meanwhile, 15.9% of patients continuing maintenance developed grade ≥2 treatment-related toxicity during maintenance.
Title: Observation versus maintenance immunotherapy after PD-1-induced clinical complete response in dMMR/MSI-H colorectal cancer managed non-operatively: a multicenter cohort study
Authors: Xiaohang Gao, Qiaoxuan Wang, Zitong Zhang, Fang He, Yi Ding, Liping Zhang, Duoduo Pei, Shaoqing Niu, Hailan Chen, Rui Sun, Ye Yao, Weiming Han, Yanjun Chen, Hui Chang, Weiwei Xiao, Liren Li, Rong Zhang, Yuanhong Gao
Read the Full Article
But what actually constitutes a complete response? Radiographically, patients may have persistent abnormalities due to fibrosis rather than viable tumor.
In my practice, I use ctDNA and biopsy, alongside imaging and endoscopy, to help guide these decisions. A residual mass doesn’t necessarily mean residual cancer.
Yes, China only. Yes, retrospective. And importantly, these were predominantly patients with localized disease who achieved cCR, not all patients with metastatic CRC.
I’ve been using these data in abstract form to guide discussions with patients almost weekly. In fact, I was literally discussing this study with Riya Patel a few hours ago, without realizing the full paper had come out.
We know immunotherapy can produce durable responses. Maybe we don’t need to keep treating patients for years…”
You can also read: 2026 Global Colorectal Cancer Congress to Showcase Health Equity Grant Recipients and Their Impact – GCCA
