Long-Term Outcomes of dMMR/MSI-H Rectal Cancer Treated With Anti-PD-1-Based Immunotherapy as Curative-Intent...

Area of Science:

• Oncology
• Gastroenterology
• Immunotherapy

Background:

• Neoadjuvant anti-PD-1 therapy demonstrates efficacy in deficient DNA mismatch repair (dMMR)/microsatellite instability-high (MSI-H) locally advanced rectal cancer (LARC).
• This approach offers potential for curative intent and organ preservation in LARC.
• Investigating long-term outcomes in patients with dMMR/MSI-H LARC who achieve clinical complete response (cCR) after anti-PD-1 therapy is crucial.

Purpose of the Study:

• To evaluate the long-term outcomes of patients with dMMR/MSI-H LARC who achieved cCR after neoadjuvant anti-PD-1 therapy.
• To assess the safety and efficacy of nonoperative management following successful neoadjuvant immunotherapy.

Main Methods:

• Retrospective analysis of 24 patients with dMMR/MSI-H LARC who achieved cCR and underwent nonoperative management.
• Data collected from 4 Chinese medical centers between March 2018 and May 2022.
• Kaplan-Meier method used for survival analysis with a minimum 1-year follow-up post-cCR.

Main Results:

• No local regrowth or distant metastasis observed in a median follow-up of 29.1 months post-cCR.
• Three-year disease-free survival and overall survival rates were both 100%.
• Fifteen patients (62.5%) continued treatment post-cCR for a median of 17.0 months.

Conclusions:

• Anti-PD-1 therapy followed by nonoperative management yields promising long-term outcomes for dMMR/MSI-H LARC patients achieving cCR.
• This strategy supports organ preservation and curative intent.
• Further validation in larger, prospective clinical trials is warranted.