Abstract S1-03: Primary results from BETH, a phase 3 controlled study of adjuvant chemotherapy and trastuzumab ± bevacizumab in patients with HER2-positive, node-positive or high risk node-negative breast cancer (2013)

Abstract Background The humanized monoclonal antibody (mAb) trastuzumab (H) + chemotherapy (chemo) prolongs disease-free survival (DFS) in patients (pts) with HER2-positive breast cancer (BC) in the adjuvant setting. Vascular endothelial growth factor (VEGF-A), one central regulator of angiogenesis, is a downstream target of HER2. Tumors overexpressing HER2 also overexpress VEGF-A and exhibit increased angiogenic potential. Combining H with the anti-VEGF-A mAb bevacizumab (B) significantly decreased tumor volume vs B or H alone in HER2-positive xenograft models and demonstrated efficacy in phase 2 studies. In the phase 3 AVEREL study in pts with HER2-positive metastatic BC, adding B to H + docetaxel (T) led to a non-significant increase in a duration of PFS and objective response rates. Chemo plus H±B is now explored in this large phase 3 trial to assess the impact of VEGF-A blockade on residual or micrometastatic disease in the adjuvant setting. Methods BETH (NCT00625898) is a randomized, phase 3, open-label study evaluating the addition of B to 2 different H-chemo regimens. Pts had centrally-confirmed HER2-positive BC (FISH+ and/or IHC 3+), ECOG PS 0-1, unilateral invasive breast adenocarcinoma, total mastectomy or lumpectomy, and LVEF ≥55%. Prior therapy with anthracyclines, taxanes, carboplatin (C), H or B for any malignancy or radiotherapy, chemo, and/or targeted therapy for the currently diagnosed BC were not permitted. Pts were stratified by center, hormone receptor status (ER and/or PR-positive, ER/PR-negative), and axillary lymph node status (0, 1-3, 4+) before inclusion into 1 of 2 chemo cohorts, and then randomized. All pts were recruited by investigators from the Translational Research in Oncology (TRIO/CIRG), the National Surgical Adjuvant Breast and Bowel Project (NSABP) or a group of independent sites. Cohort 1 (3231 pts) included pts receiving 6 cycles of TCH±B followed by H±B for 1 yr after the first dose. Cohort 2 (278 pts) included pts from some independent sites electing to use anthracycline-based therapy and these pts received 3 cycles of TH±B followed by 3 cycles of 5-fluorouracil, epirubicin, cyclophosphamide followed by H±B to complete 1 yr of treatment. T was given at 8 mg/kg IV loading dose, 6 mg/kg IV q3w thereafter; B was given at 15 mg/kg IV q3w. The primary endpoint is invasive DFS (IDFS) for B-containing vs. non-B-containing regimens. Secondary endpoints are IDFS within chemo cohorts, DFS, overall survival, recurrence-free interval (RFI), distant RFI, safety including specific cardiac assessments, and the identification of predictive biomarkers for B. The sample size was determined to test the hypothesis of interest, both in the faster accruing cohort and overall. With 3509 pts enrolled, the trial will have 85% power to detect a HR of 0.70 favoring the addition of B overall, irrespective of chemo regimen. With ∼3000 pts in the faster-accruing cohort, the study will have 80% power to detect a hazard ratio (HR) of 0.70 at a 2-sided alpha of 0.05. Median duration of follow-up will be 36 months in Jun 13, cut-off date of the primary analysis. Initial efficacy, safety, and plasma marker analyses will be reported. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr S1-03.