Key Findings:
- MutS (MSH2/MSH6 co-loss) colorectal cancer (CRC) cases trended toward longer survival.
- MutL (MLH1/PMS2 co-loss) patients had a significant OS benefit from ipilimumab/nivolumab versus pembrolizumab, independent of BRAF V600E and STK11 mutation status.
- MutS vs. MutL stratification offers a novel way to guide ICI selection in dMMR/MSI-H CRC.