Ovarian ablation or suppression in premenopausal early breast cancer: results from the international adjuvant breast cancer ovarian ablation or suppression randomized trial

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.