Second-line bevacizumab-containing therapy in patients with triple-negative breast cancer: subgroup analysis of the RIBBON-2 trial

Patients with metastatic triple-negative breast cancer (TNBC) typically have a poor prognosis and limited treatment options. To determine the impact of combining bevacizumab with second-line chemotherapy in patients with metastatic TNBC, we performed an exploratory subgroup analysis of the randomized phase 3 RIBBON-2 trial. RIBBON-2 enrolled patients with metastatic breast cancer that had progressed on first-line non-bevacizumab-containing chemotherapy. After selection of chemotherapy (taxane, gemcitabine, capecitabine, or vinorelbine), patients were randomized 2:1 to receive chemotherapy with either bevacizumab (10 mg/kg every 2 weeks or 15 mg/kg every 3 weeks) or placebo. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), objective response rate (ORR), and safety. Of 684 patients treated in RIBBON-2, 159 (23%) had TNBC. Baseline characteristics were reasonably balanced in the two treatment groups. The majority received taxane chemotherapy. The hazard ratio (HR) for PFS was 0.494 [95% confidence interval (CI) 0.33-0.74; P = 0.0006]. Median PFS was 6.0 months with bevacizumab-chemotherapy versus 2.7 months with chemotherapy alone. Median OS was 17.9 versus 12.6 months, respectively (HR 0.624, 95% CI 0.39-1.007; P = 0.0534). ORR was 41 versus 18%, respectively (P = 0.0078). The safety profile was consistent with the overall study population and previous phase 3 trials of bevacizumab. Patients with metastatic TNBC derived significant PFS and response benefits from the combination of bevacizumab with second-line chemotherapy. Despite the small sample size and immature data, there was a trend toward improved OS.