Topical estrogen prescription fill rates for women with a history of breast cancer who are taking hormone therapy

OBJECTIVE: To evaluate how often women with a history of breast cancer who are taking hormone therapy (HT) filled prescriptions for topical estrogens and whether this frequency varied over time and by type of HT used. METHODS: We performed a retrospective cohort study using medical and outpatient drug claims from a large commercial claims database for the years 2010–2015. Women younger than age 65 years taking HT for breast cancer were classified as users of 1) tamoxifen only, 2) aromatase inhibitor(s) only, or 3) any other or multiple HTs. Our outcome variable was filling a prescription for topical estrogen in a given year. We used multivariable logistic regression models estimated with generalized estimating equations to determine whether the fill rate varied over time and by HT category adjusting for age, receipt of surgical or radiation treatment, types of outpatient health care provider visits, and comorbidities. RESULTS: We identified 352,118 records from 176,012 unique patients (mean age 54.3 years, range 18–64 years) who met eligibility criteria. Aromatase inhibitors were used more commonly (56.0% of patient-years) than tamoxifen (38.8%). Overall, 3.0% (range 2.9–3.1%) of women filled any topical estrogen prescription in a given calendar year. More than half of filled topical estrogen prescriptions were for tablets (57.0%) with the remainder for creams (25.8%) and rings (17.3%). In adjusted analyses, the fill rate for women taking tamoxifen was significantly less (2.4%; 95% CI 2.3–2.5%) than for women taking aromatase inhibitors (3.3%; 95% CI 3.2–3.4%). There was a small but statistically significant increase in fill rates across years (odds ratio 1.03, 95% CI 1.02–1.04). CONCLUSION: A small proportion of women with a history of breast cancer who were taking HT filled a topical estrogen prescription, with significant differences by type of HT. More evidence is needed to inform national guidelines regarding safety and appropriate use of topical estrogens in this patient population.