Switching to anastrozole plus goserelin vs continued tamoxifen for adjuvant therapy of premenopausal early-stage breast cancer: preliminary results from a randomized trial

PURPOSE: To assess the efficacy, safety, and quality-of-life impact of switching adjuvant treatment in hormone receptor-positive primary breast cancer patients who are still premenopausal after 2–3 years of tamoxifen therapy to anastrozole plus goserelin as compared with continuing tamoxifen over a total period of 5 years. PATIENTS AND METHODS: Hormone receptor-positive, premenopausal, lymph node-positive, or tumor size ≥4 cm breast cancer patients who had received tamoxifen for 2–3 years were randomly assigned to continue tamoxifen treatment (TAM group) or switch to adjuvant anastrozole plus goserelin (ADD group) and continue treatment for another 2–3 years (total treatment duration 5 years). Endpoints evaluated were adverse events (AEs), changes in bone mineral density, quality of life, and disease-free survival-related events. RESULTS: A total of 62 patients (33 in the ADD group and 29 in the TAM group) were evaluated. Grade 3–4 drug-related AEs occurred in five patients (15.2%) in the ADD group vs none in the TAM group. In the ADD group, arthralgias were the most common AEs (5/33 patients; 15.2%), and three patients in this group were discontinued because of AEs. Treatment was temporarily suspended due to AEs in three patients (9.1%) in the ADD group and one patient (3.4%) in the TAM group. Compared with continuing TAM therapy, switching to anastrozole plus goserelin did not result in any worsening of bone mineral density or quality of life. During a median follow-up of 34 months, five patients (15.2%) in the ADD group had disease-free survival events vs four patients (13.8%) in the TAM group. CONCLUSION: For early-stage breast cancer patients who remain premenopausal following 2–3 years of adjuvant tamoxifen therapy, switching to anastrozole plus goserelin therapy was safe with tolerable adverse effects. However, it did not show superior efficacy compared to remaining on tamoxifen treatment. TRIAL REGISTRATION: ClinicalTrials.gov (identifier NCT01352091).