To test whether combining bevacizumab, an anti-vascular endothelial growth factor treatment, with endocrine therapy (ET) could potentially delay the emergence of resistance to ET.

A multicenter, randomized, open-label, phase III, binational (Spain and Germany) study added bevacizumab (15 mg/kg every 3 weeks) to ET (ET-B; letrozole or fulvestrant) as first-line therapy in postmenopausal patients with human epidermal growth factor receptor 2 (HER2) -negative and hormone receptor-positive advanced breast cancer. We compared progression-free survival (PFS), overall survival (OS), overall response rate (ORR), response duration (RD), time to treatment failure (TTF), clinical benefit rate (CBR), and safety.

From 380 patients recruited (2007 to 2011), 374 were analyzed by intent to-treat (184 patients on ET and 190 patients on ET-B). Median age was 65 years, 270 patients (72%) had Eastern Cooperative Oncology Group performance status of 0, 178 patients (48%) had visceral metastases, and 171 patients (46%) and 195 patients (52%) had received prior chemotherapy or ET, respectively. Median PFS was 14.4 months in the ET arm and 19.3 months in the ET-B arm (hazard ratio, 0.83; 95% CI, 0.65 to 1.06; P = .126). ORR, CBR, and RD with ET versus ET-B were 22% versus 41% (P < .001), 67% versus 77% (P = .041), and 13.3 months versus 17.6 months (P = .434), respectively. TTF and OS were comparable in both arms. Grade 3 to 4 hypertension, aminotransferase elevation, and proteinuria were significantly higher in the ET-B arm. Eight patients (4.2%) receiving ET-B died during study or within 30 days of end of treatment.

The addition of bevacizumab to ET in first-line treatment failed to produce a statistically significant increase in PFS or OS in women with HER2-negative/hormone receptor-positive advanced breast cancer.