Early discontinuation of tamoxifen and aromatase inhibitors (AIs) by postmenopausal women with early-stage breast cancer.

Abstract

524 Background: In women with early stage, hormone responsive breast cancer, compliance with adjuvant endocrine therapy is important for optimal outcomes. Prior studies, focused mostly on tamoxifen, have suggested suboptimal compliance, but compliance to AI therapy is little studied. We studied rates and predictors of nonpersistence in women aged 65 years and older who were treated with tamoxifen and/or AIs. Methods: A series of four telephone surveys were administered to community-dwelling women (age 65 to 89 years, median age 72) residing in 4 large states, who had initial treatment for early-stage breast cancer in 2003. The surveys, administered from 2005 to 2008, assessed demographic, socioeconomic and health factors, along with cancer treatment details, including use of adjuvant endocrine therapy. Nonpersistence was defined as a gap in adjuvant endocrine therapy of more than 60 days. Medication stop, start and switch dates were determined from survey responses. Cox proportional hazards models were used to identify patient and treatment factors that predicted nonpersistence. Results: In our cohort of 1,402 women, 55% were initially prescribed AIs, 45% tamoxifen. With median followup 59 months, 325 women (23%) discontinued treatment early (prior to 5 years). Among the 325 nonpersistent subjects, 27% discontinued therapy in the first year. Age over 80 years predicted non-persistence, risk ratio (RR) of 1.61 (p < 0.05), with a trend toward nonpersistence in women over 75 – RR 1.36 (p = 0.07). Patients in the lowest quartile of income (< $15K) had higher risk of nonpersistence (p = 0.002). Initial endocrine therapy (tamoxifen vs. AIs) was not predictive of nonpersistence. However, patients on AI's at censoring had lower nonpersistence risk, of borderline statistical significance (RR 0.80, p = 0.06). Race, marital status, education, stage, comorbidity, and type of surgery were not predictive of nonpersistence. Conclusions: Our study shows that noncompliance with standard adjuvant endocrine therapy is common in the current treatment environment. Older age and lowest income levels are associated with non-persistence. Women on AIs may be at less risk for nonpersistence. No significant financial relationships to disclose.