Ovarian Ablation or Suppression in Premenopausal Early Breast Cancer: Results From the International Adjuvant Breast Cancer Ovarian Ablation or Suppression Randomized Trial

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Abstract
Background Substantial survival benefits exist for patients with early-stage breast cancer who undergo treatment with single-modality tamoxifen, ovarian ablation or suppression, or chemotherapy. To determine whether additional benefits exist with combined treatment, the Adjuvant Breast Cancer (ABC) Trials were undertaken. Methods The ABC Ovarian Ablation or Suppression Trial randomly assigned pre- and perimenopausal patients with early-stage breast cancer who were receiving prolonged (5 years) tamoxifen treatment with or without chemotherapy to ovarian ablation or suppression (by oophorectomy, ovarian irradiation, or treatment with luteinizing hormone–releasing hormone agonist) versus no ovarian ablation or suppression. Trial endpoints included relapse-free and overall survival. Hazard ratios (HRs) were derived from Cox models, and all statistical tests were two-sided. Results Between 1993 and 2000, 2144 (1063 ovarian ablation or suppression, 1081 no ovarian ablation or suppression) patients were randomly assigned. A total of 942 (89%) received ovarian ablation or suppression as allocated. Overall, no evidence of a benefit for ovarian ablation or suppression was observed for relapse-free survival (relapse in the ovarian ablation/suppression versus no ovarian ablation/suppression group, 290 events versus 306 events, HR = 0.95, 95% confidence interval [CI] = 0.81 to 1.12; P = .56) or overall survival (death from any cause in the ovarian ablation or suppression versus no ovarian ablation/suppression group, 215 events versus 230 events, HR = 0.94, 95% CI = 0.78 to 1.13; P = .44), nor were differences seen after adjustment for age, nodal status, or estrogen receptor (ER) status. Conclusion Overall, no added effect of ovarian ablation or suppression was seen on relapse-free survival or overall survival of premenopausal women who were treated for early-stage breast cancer. However, the role of ovarian ablation or suppression in young (<40 years) women with ER-positive tumors, especially those not receiving chemotherapy, requires further study.