A randomised study of encorafenib, cetuximab, and FOLFIRI versus FOLFIRI with or without bevacizumab in BRAF V600E-mutant colorectal cancer: BREAKWATER Cohort 3

Background Encorafenib + cetuximab (EC) and mFOLFOX6 or irinotecan, leucovorin, and fluorouracil (FOLFIRI) is approved in several countries for BRAF V600E-mutant metastatic colorectal cancer (mCRC) based on results from the BREAKWATER trial. Patients and methods In BREAKWATER Cohort 3, eligible patients with previously untreated BRAF V600E-mutant mCRC were randomly assigned 1:1 to receive EC+FOLFIRI or FOLFIRI with or without bevacizumab (control). The primary endpoint was objective response rate (ORR) by blinded independent central review (BICR), and the key secondary endpoint was progression-free survival (PFS) by BICR. Other secondary endpoints included overall survival (OS) and safety. Results A total of 147 patients were randomly allocated in Cohort 3 (EC+FOLFIRI, n=73; control, n=74) with similar baseline demographics and disease characteristics across arms. EC+FOLFIRI demonstrated clinically meaningful and statistically significant improvement in ORR by BICR {64.4% versus 39.2%, odds ratio=2.756 [95% confidence interval (CI) 1.420-5.348], one-sided P-value = 0.0011}, meeting the primary endpoint (1 March 2025, data cutoff). At the 6 January 2026 data cutoff, the key secondary endpoint was met, with EC+FOLFIRI demonstrating a clinically meaningful and statistically significant PFS [hazard ratio=0.44 (95% CI 0.27-0.70), one-sided P-value = 0.0002, 15.2 versus 8.3 months]. Prolonged OS was also observed with EC+FOLFIRI (hazard ratio=0.56 [95% CI 0.34-0.94], not estimable versus 20.3 months). Serious adverse event rates were 49.3% versus 44.1% for the EC+FOLFIRI versus control arms, respectively. The safety profile was consistent with that known for each agent. Conclusions EC+FOLFIRI demonstrated clinically meaningful and statistically significant improvements in ORR and PFS, with prolonged OS versus control in BRAF V600E-mutant mCRC. The safety profile was generally manageable, with no new safety signals. These data support EC+FOLFIRI as an additional new standard of care for patients with BRAF V600E-mutant mCRC, enabling treatment personalisation.