Factors associated with adherence to medications for lowering breast cancer risk between female Medicare beneficiaries in Alabama and nationwide

Purpose The U.S. Preventive Services Task Force recommends use of selective estrogen receptor modulators (SERMs) and aromatase inhibitors (AIs) for breast cancer (BC) prevention. We examined factors associated with adherence to SERMs/AI treatments among female Medicare beneficiaries in Alabama and those nationwide. Methods This retrospective new user cohort study analyzed the 2013–2016 Medicare administrative claims data files (100% Alabama and random 5% national samples). Female Medicare beneficiaries without invasive BC and osteoporosis, continuously enrolled in Medicare Parts A, B, and D for at least 18 months (with a 6-month washout and a 12-month follow-up period) in 2013–2016. Among beneficiaries who initiated (6-month washout) any of the SERMs/AIs (tamoxifen, raloxifene, anastrozole, and exemestane), we examined their 1-year treatment adherence using proportion of days covered (PDC) and operationalized as both continuous (0–1) and dichotomized (≥ 80% as adherent and < 80% as non-adherent) outcomes. Multivariable logistic models were used to identify factors associated with adherence (PDC ≥ 80%) among Alabama and national samples, respectively. Results A total of 885 women in Alabama and 1,213 women in national sample initiated these SERMs/AI treatments. Among those with ≥ 2 prescriptions ( n = 479 in Alabama and n = 870 in national sample), Mean PDC was 0.74 [standard deviation (SD) = 0.30] among Alabamian women, similar to those in the national sample [0.71 (SD = 0.31), p = 0.09]. Use of mammography prior to treatment initiation was associated with higher likelihood of adherence to treatments in both samples. Conclusion Our findings highlight the importance of access to preventive services such as mammography to better adherence to BC preventive treatments among female Medicare beneficiaries.