Background: Among estrogens, estradiol (E2) has the strongest physiological activity as a stimulator in estrogen receptor (ER)-positive breast cancer. The aim of this study is to investigate E2 dynamics during endocrine therapy and to explore the optimal environment in which tamoxifen (TAM) exhibits better efficacy for ER-positive premenopausal early breast cancer patients.
Methods: This is a retrospective study enrolled 194 patients with premenopausal ER-positive early-stage breast cancer who aging ≤45 years at onset and receiving luteinizing hormone-releasing hormone-agonist (LHRH-a) and TAM-therapy. Approximately half of the patients also received pre- or post-operative chemotherapy as adjuvant systemic therapy. We studied the relationship between recurrence and serum hormonal dynamics during adjuvant therapy. We monitored the concentrations of E2 and, follicle-stimulating hormone (FSH) in the blood before, during, and after treatment. The median follow-up period was 80 (14-555) months.
Results: Forty-six (23.7%) patients developed recurrent breast cancer after surgery. The prognoses were favorable in the group receiving longer LHRH-a exposure if those patients did not receive chemotherapy as their adjuvant therapy. Paradoxically, patients with high serum E2 levels after LHRH-a showed a low recurrence ratio. This phenomenon might be explained by the similar mechanisms of estrogen therapy after estrogen depletion by aromatase inhibitor (AI) therapy for metastatic breast cancer.
Conclusion: Among patients who received endocrine therapy without adjuvant chemotherapy, those with longer LHRH-a exposure had favorable prognoses. A potential association was observed between recurrence and E2 concentrations in women with premenopausal ER-positive early-stage breast cancer.
Keywords: Estradiol; breast cancer; endocrine therapy; premenopausal.