The Association Between Out-of-Pocket Costs and Adherence to Adjuvant Endocrine Therapy Among Newly Diagnosed Breast Cancer Patients

OBJECTIVE: To determine how out-of-pocket costs for adjuvant endocrine therapy (AET) medication affects adherence among newly diagnosed breast cancer survivors with private health insurance who initiate therapy. METHODS: We examined medical and pharmacy claims for the 1-year period after initiating AET using the Truven Health Analytics MarketScan® database. Adherence was defined as ≥80% proportion of days covered (PDC). Mean out-of-pocket costs for AET fill were measured as the sum of copayments, coinsurance, and deductibles and adjusted to 30-day amounts. Using a multivariable logistic regression model we calculated adjusted risk ratios controlling for age, comorbidities, type of surgery, use of chemotherapy and/or radiation therapy, average out-of-pocket costs for other services, and pharmacy use characteristics. RESULTS: Of the 6,863 women 64 years and younger who were diagnosed with breast cancer and initiated AET, 73.9% were adherent (PDC≥80%). A total of 19% of patients had less than $5 monthly out-of-pocket costs for AET, 30% had $5–$9.99, 17% had $10–14.99, 10% had $15–19.99, and 25% had $20 or greater. Patients with out-of-pocket costs for AET between $10–14.99, $15–$19.99, and greater than $20 were 6–8% less likely to be adherent compared to patients paying less than $5.00, after controlling for covariates (p