Impact of Vascular Endothelial Growth Factor-A Expression, Thrombospondin-2 Expression, and Microvessel Density on the Treatment Effect of Bevacizumab in Metastatic Colorectal Cancer

Abstract

Purpose Bevacizumab is a monoclonal antibody to vascular endothelial growth factor-A (VEGF). In the pivotal trial in metastatic colorectal cancer (mCRC), addition of bevacizumab to first-line irinotecan, fluorouracil, and leucovorin (IFL) significantly prolonged median survival. The aim of these retrospective subset analyses was to evaluate VEGF, thrombospondin-2 (THBS-2), and microvessel density (MVD) as prognostic factors and/or predictors of benefit from bevacizumab. Patients and Methods In the pivotal trial, 813 patients with untreated mCRC were randomly assigned to receive IFL plus bevacizumab or placebo. Of 312 tissue samples collected (285 primaries, 27 metastases), outcome data were available for 278 (153 bevacizumab, 125 placebo). Epithelial and stromal VEGF expression were assessed by in situ hybridization (ISH) and immunohistochemistry on tissue microarrays and whole sections. Stromal THBS-2 expression was examined by ISH on tissue microarrays. MVD was quantified by Chalkley count. Overall surv...