Bevacizumab-based chemotherapy adaptive to pharmacokinetic of bevacizumab in first-line treatment of patients with unresectable metastatic colorectal cancer: A double-blind, multicenter, randomized phase III trial study (PHARBEVACOL trial).

Bevacizumab shows inter-individual pharmacokinetic variability, with an exposure-response relationship in metastatic colorectal cancer (mCRC) patients. This study explores whether a double dose of bevacizumab, compared to a standard dose, increases efficacy in mCRC patients treated with bevacizumab-based chemotherapy as first-line therapy and who have a low initial trough concentration of bevacizumab. PHARBEVACOL is a multicenter, randomized, double-blind, two-parallel group trial. All patients will receive first-line bi-weekly 5 mg/kg bevacizumab-based chemotherapy and those with low initial bevacizumab concentrations (≤15.5 mg/L) will be randomized to either continue the standard dose (5 mg/kg every 14 days) or receive a double dose (10 mg/kg every 14 days). The primary objective is to evaluate the effect of doubling dose on progression-free survival (PFS). During a screening phase, the first serum trough concentration will be measured on day 14, before the second infusion of bevacizumab. We hypothesize a 40 % PFS in the control group at 9 months versus 60 % in the study group, corresponding to a hazard ratio of 0.56. With 80 % power, a 5 % two-sided type I error, and a minimum 12-month follow-up, 116 patients need to be included. Since only 50 % of screened patients will be eligible for randomization, approximately 244 patients will be screened. Recruitment is scheduled to begin in February 2025.