Bevacizumab Pharmacokinetics Influence Overall and Progression-Free Survival in Metastatic Colorectal Cancer Patients

Clinical response to bevacizumab varies between patients treated for metastatic colorectal cancer (mCRC). The aim of this study was to quantify individual factors affecting bevacizumab pharmacokinetic variability and assess the relationship between bevacizumab concentrations and clinical outcomes. Bevacizumab pharmacokinetics were assessed in 130 mCRC patients using a two-compartment pharmacokinetic population model. Overall and progression-free survival (PFS) were analyzed using Cox models. The bevacizumab volume of distribution increased with height (p = 10(-10)) and was higher in patients with a 3/3 variable number tandem repeat of the FCGRT (Fc fragment of IgG receptor and transporter) gene (p = 0.039). The elimination rate constant increased with baseline carcinoembryonic antigen (CEA) and vascular endothelial growth factor (VEGF) concentrations, and was higher in patients with extra-hepatic metastases (p = 0.00029, 0.011, and 0.014). A bevacizumab trough concentration aecurrency sign15.5 mg/L was associated with both shorter overall survival and PFS (hazard ratio [95 % CI] 1.90 [1.20-2.99] and 1.76 [1.20-2.58], respectively). High tumour burden is associated with low bevacizumab concentrations, and high bevacizumab concentration are associated with both decreased overall and progression-free survivals.