Use of raloxifene and tamoxifen by breast cancer risk level in a Medicare-eligible cohort

Abstract

Background: Raloxifene and tamoxifen are Food and Drug Administration-approved for breast cancer risk reduction; in 2013, the US Preventive Services Task Force recommended these drugs for breast cancer risk reduction in high-risk women. Information on the use of raloxifene and tamoxifen for breast cancer risk reduction in the general population indicates that the risk is believed to be low; however, there is little literature.

Objective: The purpose of this study was to assess the use of breast cancer risk reduction medications by breast cancer risk level in an older cohort of women.

Study design: Women who were enrolled in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial were assessed for the use of raloxifene, tamoxifen, and other medications. The data sources for use of the drugs were a mailed medication use questionnaire in 2013 and linked Medicare Part D claims files from 2010-2014. Estimated breast cancer risk within 5 years was assessed with the use of the modified Gail model and self-reported breast cancer risk factors; comorbidities were assessed through a questionnaire.

Results: A total of 22,235 women completed the medication use questionnaire; of these, 13,640 women (61%) had linked Part D data. In 2013, 45% of the women were 65-74 years old, and 55% of the women were 75-84 years old. From the medication use questionnaire, raloxifene use (past month) was 1.8%, 2.5%, and 4.0% for women with breast cancer risk within 5 years of <1.66%, 1.66-3.0%, and ≥3%, respectively (probability value trend, <.0001). From Part D, for any use during the period among women with coverage, raloxifene rates were 3.3%, 4.0%, and 6.6% for the 3 categories for breast cancer risk within 5 years (probability value trend, <.0001); use was 7.4% and 3.3% in women with and without osteoporosis, respectively. Raloxifene use significantly decreased from 2010-2014, and specifically from 2012-2014, both for all women and for women with breast cancer risk within 5 years of ≥3%. Tamoxifen use from Part D was 0.36%, 0.45%, and 0.85% for the 3 categories for breast cancer risk within 5 years (probability value trend, .009).

Conclusion: Raloxifene use was low overall but increased modestly with breast cancer risk, and usage decreased from 2010-2014. Tamoxifen use was very low.

Keywords: breast cancer; chemoprevention; raloxifene; risk; tamoxifen.

Figure 1. Study flowchart

Flowchart shows which PLCO women were eligible for the current analysis. Year(s) in parenthesis is time of the event. To be eligible for transfer to active centralized follow-up in 2011 (2^nd box), subjects had to be alive, not lost to follow-up, and not at the University of Alabama at Birmingham (UAB); UAB subjects transferred to centralized follow-up later and were not eligible for the MUQ. Having part D coverage was defined as at least 12 months of coverage during the period. Colored boxed represent women included in the overall analysis (blue box) and the sub-analysis of Medicare claims data (purple box).

Figure 2. Raloxifene rates over time

Raloxifene use (prescriptions filled) by calendar year from Part D claims data. The usage rate in a given year was calculated as the proportion of women with full coverage in that year who had at least one prescription filled in that year. Black line is all women, blue solid and dotted line are women with and without osteoporosis, respectively, red line is all women with 5-year breast cancer risk of at least 3% and purple line is women with at least 3% breast cancer risk and no osteoporosis.

Figure 3. Usage rates of statins and raloxifene by risk level

Rates of use of raloxifene (blue bars) and statins (black bars) from Part D data by cardiovascular disease (CVD) risk level and five-year breast cancer risk category. High CVD risk is defined as history of diabetes, high cholesterol, heart attack or stroke; low risk is all women not at high risk.