First Report of Long-Term Responders to First-Line Bevacizumab (BEV) Combined With Chemotherapy in Two Independent Cohorts of HER2-Neg Metastatic Breast Cancer Patients (PTS) With Hormone Receptor –Positive (HR+) and Triple-Negative (TN) Tumors

ABSTRACT Background First-line BEV combined with weekly paclitaxel, docetaxel or other chemotherapy significantly improves progression-free survival (PFS) in HER2-negative metastatic breast cancer (mBC), as shown in E2100, AVADO and RIBBON-1 trials. In the ATHENA study, 21% of pts continued BEV for ≥1 year with no new safety outcome and a time to progression of 19.9 months (95% CI 18.9-21.8 months). To further understand and provide insight into the efficacy and safety of long-term responders to first-line BEV, we conducted a descriptive study of 2 different cohorts of pts with mBC: HR+ and TN, treated in routine oncology practice with at least 1 year of first-line BEV. Methods Pts who had received first-line BEV(≥1 year) associated to chemotherapy were retrospectively included in the 2 independent cohorts and followed up, if they were alive at inclusion, for 18 months. Clinico-pathological characteristics, treatment received, efficacy and safety data were collected. Results The recruitment of the TNBC cohort was just completed (n = 80) and results will be presented at the meeting. In the HR+ cohort (n = 132), 28.1% of the pts had a disease-free interval 3 metastatic sites at diagnosis, and more than 1/3 of the patient had lung and/or liver involvement. In association to 1st line BEV, 93,2% had received a taxane as initial 1st line chemotherapy, 76.2% had received maintenance endocrine therapy and 4.2% had received maintenance chemotherapy (capecitabine). Best response obtained in 1st line was a complete response or partial response for 84,6%. With a median follow-up of 33 months, median PFS was 27.4 months (95% CI [23.2-33.8]). Overall survival data were immature as 84.8% of the pts were alive at inclusion. The most common BEV related grade 3/4 adverse events were hypertension (7.5%), bleeding (1.9%), proteinuria (1.3%) and congestive heart failure (1.3%). Conclusion Prolonged BEV-containing therapy in this HR+ cohort is of interest and suggests that some pts achieve sustained disease control with limited side effects. Disclosure V. Dieras: Advisory boards and Symposium participation. H. Simon: Member of an advisory board: Roche Mastology Group. N. Mesnard: Roche employee. E. Antoine: Membership of an advisory board. All other authors have declared no conflicts of interest.