PD1 blockade for advanced MSI-H CRC

In a phase III, open-label trial, 307 treatment-naive patients with metastatic microsatellite-instability-high (MSI-H)–mismatch-repair-deficient colorectal cancer were randomly assigned to either pembrolizumab or 5-fluorouracil-based therapy with or without bevacizumab or cetuximab as first-line treatment. At a median follow-up 32.4 months, patients in the pembrolizumab group had higher progression-free survival than patients in the chemotherapy group (median 16.5 versus 8.2 months; HR 0.60; 95% CI 0.45–0.80; P = 0.0002). 43.8% of the pembrolizumab group and 33.1% of the chemotherapy group had an overall response. Serious treatment-related adverse effects were lower in the pembrolizumab group.