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

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.