Adding Ovarian Suppression to Tamoxifen for Premenopausal Women With Hormone Receptor–Positive Breast Cancer After Chemotherapy: An 8-Year Follow-Up of the ASTRRA Trial

PURPOSE To determine the updated long-term outcomes of the Addition of Ovarian Suppression to Tamoxifen in Young Women With Hormone-Sensitive Breast Cancer Who Remain Premenopausal or Regain Vaginal Bleeding After Chemotherapy (ASTRRA) trial. PATIENTS AND METHODS This study is a post-trial follow-up of the ASTRRA trial, involving 1,483 premenopausal women younger than 45 years treated with definitive surgery after completing adjuvant or neoadjuvant chemotherapy for estrogen receptor–positive breast cancer. Patients were randomly assigned in a 1:1 ratio to complete 5 years of tamoxifen (TAM) alone (TAM-only) or 5 years of TAM with ovarian function suppression (OFS) for 2 years (TAM + OFS). The primary end point was disease-free survival (DFS), and the secondary end point was overall survival (OS). RESULTS At 106.4 months of median follow-up, there was a continuous significant reduction in the DFS event rate in the TAM + OFS group. The 8-year DFS rate was 85.4% in the TAM + OFS group and 80.2% in the TAM-only group (hazard ratio [HR], 0.67; 95% CI, 0.51 to 0.87). There were no significant differences in OS between the two groups. The OS rate was 96.5% in the TAM + OFS group and 95.3% in the TAM-only group (HR, 0.78; 95% CI, 0.49 to 1.25). CONCLUSION Adding OFS for 2 years to adjuvant TAM with a longer follow-up resulted in consistent DFS benefits, suggesting that adding OFS to TAM should be considered for patients who remain in a premenopausal state or resume ovarian function after chemotherapy.