Randomized study to investigate FOLFOXIRI plus either bevacizumab or cetuximab as first-line treatment of BRAF V600E-mutant mCRC: The phase-II FIRE-4.5 study (AIO KRK-0116).

3502 Background: FIRE-4.5 (AIO KRK-0116) compared FOLFOXIRI plus either cetuximab or bevacizumab in BRAF V600E-mutant metastatic colorectal cancer (mCRC) patients not treated for metastatic disease before. Methods: Within this 1:2 randomized, controlled, open-label phase-II study, patients received FOLFOXIRI every two weeks at the following schedule: irinotecan 150mg/m² (30-90min, day 1), folinic acid 400mg/m² (120min, day 1), oxaliplatin 85mg/m² (120 min, day 1), followed by 5-fluorouracil 3,000 mg/m², 48h. FOLFOXIRI was combined with either bevacizumab (arm A) at a dose of 5mg/kg body weight, every 2 weeks or cetuximab (arm B) at a loading dose of 400mg/m² and subsequent weekly doses of 250mg/m². FOLFOXIRI was applied for a maximum of 12 cycles before maintenance treatment was recommended. Primary endpoint was superiority of Arm B with respect to overall response rate (ORR) according to RECIST 1.1 criterions. Secondary endpoints included PFS, OS, and tolerability. Results: From November 2016 to December 2020 108 patients were randomized in 90 German and 10 French centers (35 arm A and 73 in arm B). No new or unexpected toxicities were observed. Primary endpoint was not met with an ORR of 66.7% and 52.0% (p =0.23) in the respective arms. Median PFS was significantly longer in arm A vs arm B (8.3 months vs 5.9 months; logrank p = 0.03; HR 1.8). While OS data is still immature, median OS time are comparable at the time of analysis. Patients with left-sided primary tumors had comparable results with either bevacizumab or cetuximab, whereas those with right-sided primary tumors showed a trend towards better efficacy of the bevacizumab combination. Updated results will be presented at the annual meeting. Conclusions: FIRE-4.5 is the first prospective and randomized study investigating efficacy of FOLFOXIRI combined with targeted therapy in the first-line treatment of BRAF V600E-mutant mCRC. FOLFOXIRI plus either bevacizumab or cetuximab have comparable efficacy with differential effects according to primary tumor sidedness supporting the heterogeneity of BRAF V600E-mutant subpopulation of mCRC. Clinical trial information: NCT04034459.