• Division of Cancer Prevention, National Cancer Institute, Bethesda, MD, United States. Electronic address: pp4f@nih.gov.
• Division of Cancer Prevention, National Cancer Institute, Bethesda, MD, United States.

BACKGROUND: Guidelines recommend the breast cancer risk reducing medications (RRMs) tamoxifen, raloxifene, and aromatase inhibitors (AIs) for women at increased breast cancer risk. However, use of RRMs in this population is low. We assessed RRM trends in older women enrolled in a cancer screening trial.

METHODS: We analyzed a cohort of women enrolled in the Prostate, Lung, Colorectal, and Ovarian (PLCO) screening trial who consented to linkage with Medicare files, were enrolled in Medicare Part D during 2014-2019, and for whom a breast cancer risk score could be computed. Breast cancer risk using the BCRAT model was ascertained based on questionnaire data. We assessed use of RRMs overall, by breast cancer risk level, and over time.

RESULTS: Of 78,209 women enrolled in PLCO, 14,081 were included in the analysis cohort based on consenting to Medicare linkage and enrollment in Medicare Part D. Median (25th/75th) age in 2014 was 75(72/79). Use of any RRM during 2014-2019 was 3.6 %, with raloxifene the most common medication (3.1 %), followed by AIs (0.45 %) and tamoxifen (0.11 %). Use of any RRM, raloxifene and AIs each increased significantly with breast cancer risk level. Among women with 5-year risk ≥ 3 %, use of any RRM was 5.3 %. Over time, use of any RRM and raloxifene decreased significantly (5.7 % and 7.5 % average annual decrease, respectively); use of AIs increased significantly (16.3 %).

CONCLUSIONS: Use of breast cancer RRMs was low, overall and among women with increased breast cancer risk. Overall RRM and raloxifene use decreased over time, while AI use increased.