Supplementary Material for: Persistence to adjuvant endocrine treatment 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 non-persistent patients.

Results:
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%) of patients, however, only 8 (8.8%) were non-persistent. Sociodemographic and clinical characteristics were similar between persistent and non-persistent 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.