COMMIT: A Randomized Study of mFOLFOX6/Bevacizumab/Atezolizumab or Atezolizumab Alone as First-Line Treatment of Deficient DNA Mismatch Repair Metastatic Colorectal Cancer

PURPOSE Immunotherapy for frontline mismatch repair–deficient/microsatellite instability-high (dMMR/MSI-H) metastatic colorectal cancer (mCRC) is effective; however, nearly half of the patients treated with single-agent PD-1 therapy will progress within 12 months. Preclinical studies in CRC and clinical data from other cancers suggest that vascular endothelial growth factor inhibition and chemotherapy can synergize with PD-L1 inhibition. METHODS The NRG-GI004/SWOG-S1610 (COMMIT) three-arm prospective phase III open-label trial randomly assigned first-line dMMR/MSI-H mCRC patients (1:1:1) to either: mFOLFOX6 (oxaliplatin 85 mg/m², leucovorin 400 mg/m², 5-FU bolus 400 mg/m², and 46-hour infusional 5-FU 2,400 mg/m²)/bevacizumab (FFX/bev), or atezolizumab (atezo) monotherapy (840 mg IV once every 2 weeks), or the combination of FFX/bev/atezo. The primary end point was progression-free survival (PFS) in the intent-to-treat population. Because of KEYNOTE 177 results, the FFX/bev arm was closed after 20 patients were enrolled. The study continued with atezo alone versus FFX/bev/atezo, with a revised sample size of 100 patients in the two remaining arms (120 patients across all three arms). RESULTS From November 2017 to March 2025, a total of 102 patients were enrolled in the three arms: FFX/bev: n = 20, atezo: n = 41, and FFX/bev/atezo: n = 41. At a median follow-up of 46 months for the two arms (median age: 63.3 years; 47.6% female; 23.2% BRAF V600E mutated), PFS of FFX/bev/atezo was superior to that of atezo (hazard ratio [HR], 0.439 [95% CI, 0.23 to 0.84]; P = .0103) and below the critical value of 0.0152. The objective response rate was 86.1% versus 46%, and the disease control rate at 12 months was 64.7% versus 32.4% in the FFX/bev/atezo arm compared with the atezo-only arm, respectively. Grade 3 or higher adverse events of any attribution occurred in 52 patients (atezo: 18; combination arm: 34). CONCLUSION The combination of FFX/bev plus atezo led to significantly longer PFS compared with atezo monotherapy in the first-line treatment of dMMR/MSI-H mCRC.