Persistence to Adjuvant Endocrine Therapy for Breast Cancer in Botswana: An Observational Cohort Analysis.

Purpose: Daily use of adjuvant endocrine therapy significantly reduces the risk of recurrence and death of estrogen-positive breast cancer; however, it remains unclear to what degree patients persist with endocrine therapy in southern Africa. Methods: Female patients, >18 years of age, with estrogen receptor-positive breast cancer within the Thabaste Cancer Cohort in Botswana were identified and contacted to determine if they remained persistent to their adjuvant endocrine therapy. Non-persistence was defined as self-reported discontinuation of endocrine therapy for longer than 180 days. Clinical and demographic data were compared between persistent and nonpersistent patients. Results: Overall, 133 patients with estrogen receptor-positive breast cancer were identified of which 91 were prescribed adjuvant endocrine therapy. Tamoxifen was prescribed for 56 (63%) and anastrozole for 33 (37%) women. Adjuvant endocrine therapy was interrupted in 45 (50%) patients; however, only 8 (8.8%) were nonpersistent. Sociodemographic and clinical characteristics were similar between persistent and nonpersistent patients, except significantly higher income was noted in those persistent to endocrine therapy. Medication non-availability was the most common reason noted for interruption of endocrine therapy. Conclusion: Interruptions to adjuvant endocrine therapy in Botswana is common, but rates of persistence remain high. Medication stockout was the most common reasons for interruption of adjuvant endocrine therapy.