Nonadherence to Oral Medications for Chronic Conditions in Breast Cancer Survivors.

PURPOSE: Nonadherence to oral endocrine therapy is common among women with breast cancer (BC). Less is known about nonadherence to medications for other chronic conditions among survivors of BC.

METHODS: We used the MarketScan Database to identify women older than 18 years who had nonmetastatic BC diagnosed between January 1, 2009, and December 31, 2013. Prescriptions were identified for the following six non-cancer-related conditions: hypertension, thyroid disease, hyperlipidemia, gastroesophageal reflux disease, diabetes, and osteoporosis. The study period was defined as 1 year before BC diagnosis (index date) through 1.5 years after the index date, with a 6-month washout period after the index data to control for adherence during the preoperative period and during chemotherapy if necessary. Adherence was defined as a medication possession ratio ≥ 80%. Change in adherence was defined as a 20% decrease in the medication possession ratio from the time before diagnosis compared with after treatment. Factors associated with change in adherence were evaluated in multivariable logistic models.

RESULTS: Among 36,149 patients diagnosed with BC, the average adherence to these medications before BC was 91.4%. However, after BC treatment, adherence decreased to 77.9% (P < .001). Looking at drugs for each condition, nonadherence ranged from 15.6% to 38% (P < .001). Factors associated with an increase in nonadherence included older age, insurance type, number of medications, and comorbid conditions.

CONCLUSION: Decreased adherence to medications for chronic diseases was found in the first year after breast cancer treatment. Breast cancer survivors may need additional interventions to improve their adherence to their medications for chronic conditions.