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.

Materials And 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. 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 6863 women 64 years and younger who were diagnosed with breast cancer and initiated AET, 73.9% were adherent (proportion of days covered≥80%). A total of 19% of patients had <$5 monthly out-of-pocket costs for AET, 30% had $5 to $9.99, 17% had $10 to $14.99, 10% had $15 to $19.99, and 25% had $20 or greater. Patients with out-of-pocket costs for AET between $10 and $14.99, $15 and $19.99, and >$20 were 6% to 8% less likely to be adherent compared with patients paying <$5.00, after controlling for covariates (P<0.05). Out-of-pocket costs for inpatient, outpatient, and other pharmacy services were not associated with adherence.

Conclusions: A substantial proportion of privately insured patients are nonadherent to AET and out-of-pocket costs for AET medication are significantly associated with a greater likelihood of nonadherence.