Effects of Previous Medication Regimen Factors and Bipolar and Psychotic Disorders on Breast Cancer Endocrine Therapy Adherence.

BACKGROUND: Endocrine therapy adherence remains a barrier to optimal estrogen receptor-positive breast cancer outcomes. We theorized that experience navigating difficult medication regimen factors, such as route of administration complexity, might improve subsequent adherence after stressful cancer diagnoses but not for patients with bipolar and psychotic disorders at risk of poor access and nonadherence. MATERIALS AND METHODS: We included 21,894 women aged ≥ 68 years at their first surgically treated stage I-IV estrogen receptor-positive breast cancer (2007-2013) from the Surveillance, Epidemiology, and End Results-Medicare data set, of whom 5.8% had bipolar or psychotic disorders. We required continuous fee-for-service Medicare (parts A and B) data for ≥ 36 months before and 18 months after the cancer diagnosis. The medication regimen factors in the part D claims for 4 months before included the number of all medications used, pharmacy visits, and administration complexity (medication regimen complexity index subscale). Cox regression analysis was used to model the time to initiation and discontinuation, with longitudinal linear regression for adherence to endocrine therapy. RESULTS: Women with more frequent previous medication use and pharmacy visits were more likely to initiate, 4+ medications and 2+ visits versus no medication (hazard ratio [HR], 1.47; 95% confidence interval [CI], 1.33-1.63), to adhere (6.0%; 95% CI, 4.3-7.6), and to continuously use their endocrine therapy (discontinuation HR, 0.48; 95% CI, 0.39-0.59). Medication administration complexity had modest effects. Difficult medication regimens were more common for patients with bipolar and psychotic disorders but had no statistically significant effects. CONCLUSIONS: Experience with frequent previous medication use and pharmacy visits might increase the likelihood of endocrine therapy use for most patients but not for those with bipolar and psychotic disorders.

Impact of preexisting mental illness on breast cancer endocrine therapy adherence.

PURPOSE: Patients with estrogen receptor positive (ER+) breast cancer are often non-adherent to endocrine therapies, despite clear survival benefits. We utilized a nationally representative cancer cohort to examine the role of specific mental illnesses on endocrine therapy adherence. METHODS: Using the SEER-Medicare database, we included 21,894 women aged 68+ at their first surgically treated stage I-IV ER+ breast cancer during 2007-2013. All had continuous fee-for-service Medicare Parts A and B for 36+ months before, 18+ months after diagnosis, and continuous Part D for 4+ months before, 18+ after diagnosis. Mental illness was defined as occurring in the 36 months prior to cancer onset. We analyzed endocrine therapy adherence, initiation, and discontinuation using longitudinal linear and Cox regression models. RESULTS: Unipolar depression (11.0%), anxiety (9.5%), non-schizophrenia psychosis (4.6%), and dementias (4.6%) were the most prevalent diagnoses. Endocrine therapies were initiated by 80.0% of women. Among those with at least one year of use, 28.0% were non-adherent (< 0.80 adherence, mean = 0.84) and 25.7% discontinued. Patients with dementia or bipolar depression/psychotic/schizophrenia disorders had lower adjusted initiation probabilities by year one of follow-up, versus those without these diagnoses [0.74 95% CI (0.73-0.74) and 0.73 (0.72-0.73), respectively, reference 0.76 (0.76-0.77)]. Patients with substance use or anxiety disorders less frequently continued endocrine therapy for at least one year, after adjustment, [0.85 95% CI (0.85-0.86) and 0.88 (0.87-0.88), respectively, reference 0.90 (0.89-0.90)]. Patients with substance use disorders had 2.3% lower adherence rates (p < 0.001). CONCLUSIONS: Nearly one-quarter of female Medicare beneficiaries have diagnosed mental illness preceding invasive breast cancer. Those with certain mental illnesses have modestly reduced rates of initiation, adherence, and discontinuation and this may help define patients at higher risk of treatment abandonment. Overall, endocrine therapy adherence remains suboptimal, unnecessarily worsening recurrence and mortality risk.