Nonadherence to Medications for Chronic Conditions and Nonadherence to Adjuvant Hormonal Therapy in Women With Breast Cancer

IMPORTANCE While adjuvant hormonal therapy (HT) reduces mortality for women with nonmetastatic breast cancer, nonadherence to HT is common. OBJECTIVE We investigated the association between patterns of prior nonadherence to medications for chronic conditions with HT nonadherence. DESIGN, SETTING, AND PARTICIPANTS For this retrospective cohort study, the MarketScan database was scanned for women 18 years and older who had been diagnosed with nonmetastatic breast cancer between January 1, 2010, and December 31, 2012, and who filled 2 or more prescriptions for tamoxifen and/or an aromatase inhibitor. MAIN EXPOSURES AND OUTCOMES Nonadherence to medications for 6 chronic conditions (hypertension, hyperlipidemia, gastroesophageal reflux disease, thyroid disease, diabetes, osteoporosis) in the 12 months before diagnosis was defined as a medication possession ratio (MPR) less than 80%. Nonadherence to HT was defined as an MPR less than 80% between the first and last prescription for HT up to 2 years. ANALYSIS Multivariable logistic regression was used to determine the association between prior medication nonadherence and HT nonadherence. RESULTS Of 21 255 women treated with adjuvant HT, 3314 (15.6%) were nonadherent, and age (< 55 or >= 75 years vs 55-64 years), higher 30-day out-of-pocket costs, and increased comorbidities were associated with nonadherence. Women without prior medications for 1 of the chronic conditions (n = 7828 [37%]) had an 18.4% nonadherence rate to HT. Those who used 1 or more medication prior to HT and were adherent (n = 9223 [43%]) had a 9.8% nonadherence rate to HT (relative to those without prior medications: odds ratio [OR] 0.56; 95% CI, 0.50-0.61), while those who were nonadherent to their chronic medications (n = 4214 [20%]) had a 23.1% nonadherence rate to HT (OR 1.43; 95% CI, 1.30-1.58). Adherence and nonadherence for medications for each of the 6 medical conditions was associated with adherence or nonadherence for HT, respectively. CONCLUSIONS AND RELEVANCE We found that nonadherence to medications for chronic conditions prior to HT was associated with greater nonadherence to oral HT in patients with breast cancer. Medication nonadherence history may play an important role in determining patients at risk for nonadherence to a subsequent medication for a different illness, such as HT, and a potential target for future interventions.