Evaluation of Adjuvant! Online to predict the effect of optimal endocrine therapy (ovarian function suppression plus tamoxifen) for premenopausal breast cancer patients with estrogen-receptor-positive breast cancer

Abstract

585 Background: Adjuvant! Online (AOL) is a user-friendly, web-based tool that provides estimates of adjuvant therapy outcomes for individual patients. While reliable evidence underpins estimates for most patient cohorts, there is a paucity of data on the effect of adding chemotherapy to complete estrogen blockade for premenopausal women with estrogen-receptor positive breast cancer. Methods: International Breast Cancer Study Group (IBCSG) Trial 11–93 enrolled 174 premenopausal women with estrogen-receptor positive, node-positive breast cancer from 1993 to 1998. Fifty percent of patients had 1 positive axillary lymph node and 97% had between 1 and 3 positive nodes. Patients were randomized to receive ovarian function suppression plus five years of tamoxifen with or without chemotherapy. The estimated hazard rates and corresponding 10-year relapse-free survival percents obtained from Trial 11–93 data (Breast Cancer Res Treat. 2009;113:137–144) were compared with those predicted using AOL. Results: The 10-year relapse-free survival percents predicted from AOL were 64.4% (95% CI, 61.9% to 67.2%) for endocrine therapy alone and 74.9% (95% CI, 73.1% to 76.8%) for chemoendocrine therapy. By contrast, these estimates in Trial 11–93 were 76.4% (95% CI, 65.8% to 84.0%) for endocrine therapy alone and 74.9% (95% CI, 64.5% to 82.7%) for chemoendocrine therapy. The AOL estimate for the endocrine alone control group is lower than that observed in Trial 11–93 (p = 0.03), while the estimates for the two chemoendocrine therapy groups are similar. Conclusions: AOL appears to underestimate the effectiveness of adjuvant endocrine therapy alone for premenopausal women with endocrine responsive breast cancer, thus overestimating the added benefit - if any - from chemotherapy for this patient population. Prospective clinical trials addressing the question are warranted. No significant financial relationships to disclose.