Prognostic role of human epidermal growth factor receptor 2 status in premenopausal early breast cancer treated with adjuvant tamoxifen.

Estrogen receptor positivity is usually considered the main predictive factor of clinical benefit for endocrine therapy in breast cancer; however, some patients who are estrogen receptor positive fail to respond to tamoxifen. To better understand this matter, we reviewed 425 early breast cancer treated with exclusive tamoxifen by focusing on human epidermal growth factor receptor 2 status. Background: Hormone therapy is the most prescribed systemic therapy for patients with breast cancer (BC). Some patients fail to respond to tamoxifen; one pathway seems to involve human epidermal growth factor receptor 2 (HER2) overexpression. To better understand this matter, we reviewed our single-center experience of premenopausal patients who were chemotherapy naive and treated with 5 years of tamoxifen for early-stage BC by focusing on estrogen receptor (ER), progesterone receptor, HER2 status, and Ki-67 proliferative index. Patients and Methods: We reviewed 425 patients treated with tamoxifen for early-stage BC. Previous solid tumors, age less than 18 years, BC recurrences or contralateral tumor, tamoxifen discontinuation, adjuvant chemotherapy, and a follow-up shorter than 6 months were considered exclusions criteria of the study. Results: At a mean follow-up of 8.1 years, the mean (SD) time to local relapse was 6.7 ± 3.6 years; range, 2.0-10.7 years), whereas the mean (SD) time to distant metastases was 4.7 ± 2.3 years; range, 2.2-8.8 years). HER2 status did not influence local relapse-free survival (log-rank test, 0.40), distant metastases-free survival (log-rank test, 0.72), and overall survival rate (log-rank test, 0.87). Conclusions: Resistance to tamoxifen is a complex trait, and its pathway is still unclear; in patients with BC, a multidisciplinary approach is highly recommended. In our experience, we did not find a statistically significant difference in tamoxifen treatment efficacy according to HER2 status.