Extended endocrine therapy use and decision making after breast cancer diagnosis

Purpose Adjuvant endocrine therapy is recommended to extend beyond five years for stage II breast cancer, with less consensus for extension in stage I. We aimed to understand use of and decision-making about extended endocrine therapy. Patients and Methods Women aged 20-79 diagnosed with stage I-II breast cancer in 2014-15 and reported to Georgia and Los Angeles County SEER registries were surveyed at seven months and again at six years post-diagnosis (N = 2,361; response rate = 60%). Women with estrogen receptor (ER) and/or progesterone receptor (PR)-positive disease were asked about their decision whether to continue therapy. Results Of 831 women, 591 had completed or were completing five years of endocrine therapy. Among those who had decided (n = 557), 46.9% decided to continue (39.4% stage I, 62.4% stage II). On multivariable analysis, factors associated with continuation for stage I were worry about recurrence (adjusted odds ratio (aOR) 3.35, 95% confidence interval (CI) 1.78-6.32); desire for most extensive treatment (aOR 2.15; CI 1.11-4.14); and primary care physician participation (aOR 4.30; CI 2.22-8.32). Side effects were inversely associated with continuation (stage I aOR 0.21: CI 0.11-0.41). Associations were similar for stage II; for stage I only, bilateral mastectomy and chemotherapy were associated with continuation. Decision to continue did not vary by race, ethnicity or demographic factors. Conclusions Nearly 40% of women with stage I breast cancer, and two-thirds with stage II, decided to extend endocrine therapy. Decision-making was influenced by patient values and varied little by stage. These results can inform physician-patient discussion about extending endocrine therapy.