Long Term Cohort Study of Adding Ovarian Function Suppression to Tamoxifen in Young Women

This study evaluates the long-term effects of adding 2 years of ovarian function suppression (OFS) to tamoxifen therapy in young premenopausal women with hormone receptor-positive breast cancer after chemotherapy. The study will assess recurrence, breast cancer-specific survival, and overall survival beyond 10 years to determine the long-term benefits of OFS treatment.

Inclusion Criteria: * Premenopausal women with hormone receptor-positive breast cancer enrolled in the ASTRRA trial (NCT00912548). Patients enrolled and randomized in the ASTRRA study between March 1, 2009, and July 17, 2018 (excluding screening failures). Patients with available long-term follow-up information. Exclusion Criteria: * Patients with primary breast cancer meeting any of the following criteria: Hormone receptor-negative breast cancer Unknown hormone receptor status Patients with a history of hysterectomy or bilateral oophorectomy Patients with breast sarcoma or squamous cell carcinoma of the breast Patients with a history of malignancy other than breast cancer within 5 years prior to enrollment Patients with thrombocytopenia Patients who had previously received CMF chemotherapy (cyclophosphamide, methotrexate, and fluorouracil)