Adding hormonal therapy to chemotherapy and trastuzumab improves prognosis in patients with hormone receptor-positive and human epidermal growth factor receptor 2-positive primary breast cancer

Adjuvant hormonal therapy for hormone receptor (HR)-positive primary breast cancer patients and a human epidermal growth factor receptor 2 (HER2)-targeted agent for HER2-positive primary breast cancer patients are standard treatment. However, it is not well known whether adding hormonal therapy to the combination of preoperative or postoperative chemotherapy and HER2-targeted agent contributes any additional clinical benefit in patients with HR-positive/HER2-positive primary breast cancer regardless of cross-talk between HR and HER2. We retrospectively reviewed records from 897 patients with HR-positive/HER2-positive primary breast cancer with clinical stage I–III disease who underwent surgery between 1988 and 2009. We determined the overall survival (OS) and disease-free survival (DFS) rates according to whether they received hormonal therapy or not and according to the type of hormonal therapy, tamoxifen and aromatase inhibitor, they received. The median followup time was 52.8 months (range 1–294.6 months). Patients who received hormonal therapy with chemotherapy and trastuzumab (n = 128) had significantly higher OS and DFS rates than did those who received only chemotherapy and trastuzumab (n = 46) in log-rank analysis (OS 96.1 vs. 87.0 %, p = 0.023, DFS 86.7 vs. 78.3 %, p = 0.029). There was no statistical difference in OS or DFS between those given an aromatase inhibitor and those given tamoxifen. In multivariate analysis, receiving hormonal therapy in addition to the combination of chemotherapy and trastuzumab was the sole independent prognostic factor for DFS (hazard ratio 0.446; 95 % CI 0.200–0.992; p = 0.048), and there was a similar trend in OS. Our study supported that hormonal therapy, whether in the form of an aromatase inhibitor or tamoxifen, confers a survival benefit when added to chemotherapy and trastuzumab in patients with HR-positive/HER2-positive primary breast cancer. Adjuvant treatment without hormonal therapy is inferior for this patient population.