Progression-free survival (PFS) in postmenopausal women with hormone receptor-positive metastatic breast cancer (MBC) was improved with the addition of bevacizumab to letrozole, but this benefit was associated with a significantly increased risk of grade 3 to 4 toxicities. This according to a phase III trial of 350 women (median age 58 years) with hormone receptor-positive MCB who were randomly assigned 1:1 to letrozole (2.5 mg orally per day) with or without bevacizumab (15 mg/kg intravenously once every 3 weeks). Researchers found:
• At a median follow-up of 39 months, the addition of bevacizumab resulted in a significant reduction in the hazard of progression (HR=0.75) and a prolongation in median PFS from 15.6 months with letrozole to 20.2 months with letrozole plus bevacizumab.
• There was no significant difference in overall survival (HR=0.87) with median OS of 43.9 months with letrozole vs 47.2 months with letrozole plus bevacizumab.
• The largest increase in incidence of grade 3 to 4 treatment-related toxicities with the addition of bevacizumab were hypertension and proteinuria.
Citation: Dickler MN, Barry WT, Cirrincione CT, et al. Phase III trial evaluating letrozole as first-line endocrine therapy with or without bevacizumab for the treatment of postmenopausal women with hormone receptor-positive advanced-stage breast cancer: CALGB 40503 (Alliance). [Published online ahead of print May 2, 2016]. J Clin Oncol. doi:10.1200/JCO.2015.66.1595.