Optimal First-Line Immunotherapy for MSI-H/dMMR Metastatic Colorectal Cancer: Evidence, Gaps, and Clinical...

Area of Science:

• Oncology
• Immunotherapy
• Gastrointestinal Oncology

Background:

• Microsatellite instability-high (MSI-H) or mismatch repair-deficient (dMMR) metastatic colorectal cancer (mCRC) is a key area for biomarker-driven immunotherapy.
• Optimal first-line treatment positioning for immunotherapy agents like pembrolizumab and nivolumab (alone or combined with ipilimumab) remains an area of active investigation in routine practice.

Purpose of the Study:

• To review landmark and contemporary evidence for immunotherapy in MSI-H/dMMR mCRC.
• To evaluate the efficacy, safety, and optimal clinical positioning of single-agent and combination immunotherapies in the first-line setting.

Main Methods:

• Narrative review of key clinical trials including KEYNOTE-164, KEYNOTE-177, CheckMate 142, CheckMate 8HW, and the COMMIT trial.
• Inclusion of high-quality non-randomized cohort studies and ongoing trial data to provide a comprehensive overview.

Main Results:

• Pembrolizumab is established as a first-line standard with superior progression-free and overall survival compared to chemotherapy, alongside a favorable safety profile.
• Nivolumab plus ipilimumab demonstrates superior efficacy over chemotherapy and nivolumab monotherapy but is associated with significantly higher immune-related toxicity and treatment discontinuation.
• Chemo-immunotherapy combinations show potential, as suggested by the COMMIT trial, though further data is needed for definitive interpretation.

Conclusions:

• Treatment selection for MSI-H/dMMR mCRC requires balancing evidence strength, toxicity, patient fitness, and biomarker confidence, especially given the lack of direct head-to-head comparisons.
• Ongoing trials and survival analyses will further refine optimal first-line immunotherapy strategies.