mFOLFOX6/Bevacizumab + Atezolizumab (PD-L1) Extends PFS vs Atezolizumab Alone in 1L dMMR/MSI-H mCRC

NRG-GI004/SWOG S1610 (COMMIT; Phase III, open-label) randomized patients with previously untreated dMMR/MSI-H metastatic colorectal cancer to atezolizumab (PD-L1 antibody) monotherapy vs mFOLFOX6 + bevacizumab (VEGF inhibitor) + atezolizumab (n=41/arm; total enrolled n=102); an original chemotherapy/bevacizumab-only arm closed early after KEYNOTE-177 established checkpoint inhibition as the frontline standard. At median follow-up of 46 months, adding mFOLFOX6/bevacizumab improved PFS vs atezolizumab alone (HR 0.439; 95% CI 0.23–0.84; p=0.0103), increased ORR to 86.1% vs 46%, and increased 12-month disease control to 64.7% vs 32.4%, but grade ≥3 AEs were substantially more common (34 vs 18 patients). The key modern benchmark is no longer chemotherapy: PD-1–based therapy is already highly active in 1L MSI-H/dMMR mCRC. Pembrolizumab remains an established frontline option, while nivolumab + ipilimumab is now FDA-approved and in CheckMate 8HW produced median PFS not reached vs 5.8 months with chemotherapy (HR 0.21). That raises the more clinically relevant question for COMMIT: whether adding chemotherapy and VEGF blockade to checkpoint inhibition provides enough additional early disease control to justify the added toxicity over contemporary PD-1–based approaches.