Polypharmacy and Adherence to Adjuvant Endocrine Therapy for Breast Cancer

Many patients with breast cancer are treated for other conditions and experience polypharmacy with multiple concurrent medications. Our aim was to evaluate polypharmacy in relation to adherence to adjuvant endocrine therapy (AET) in breast cancer.

We conducted a retrospective cohort study of women with incident, invasive breast cancer initiating AET (tamoxifen, letrozole, anastrozole, exemestane) between 2009 and 2013 in the Truven Health MarketScan Database. Polypharmacy and pill burden were measured for commonly used concurrent medications, including lipid-lowering drugs, antihypertensives, oral diabetes medications, insulin analogs, antidepressants, anxiolytics/antipsychotics, and opioid-containing analgesics. Polypharmacy was defined as frequent use (three or more dispensings) of a given medication class and by pill burden (total dispensings). Medication possession ratios (MPR) were estimated for subsequent 12-month intervals. Multivariable generalized estimating equation models were used to calculate odds ratios (ORs) and robust 95% CIs for associations with AET adherence (MPR ≥ 0.80).

Among 40,009 women, 74% were adherent in year +1 and continued to have high mean adherence (MPR = 0.79) among those continuing AET through year +3. Increasing polypharmacy ( P < .001) and pill burden ( P < .001) were associated with greater adherence, but effects differed by medication class. Frequent use of lipid-lowering drugs (OR, 1.42; 95% CI, 1.36 to 1.49) and antihypertensives (OR, 1.15; 95% CI, 1.10 to 1.20) were associated with higher odds of adherence; frequent use of opioid-containing analgesics (OR, 0.80; 95% CI, 0.77 to 0.83), anxiolytics/antipsychotics (OR, 0.95; 95% CI, 0.91 to 0.99), antidepressants (OR, 0.85; 95% CI, 0.82 to 0.89), and insulin therapy (OR, 0.82; 95% CI, 0.72 to 0.95) were associated with lower odds of adherence.

Associations between polypharmacy and adherence in breast cancer may be better characterized by understanding specific classes of medications used concurrently. Comprehensive medication therapy management, including ongoing pain evaluation and psychoactive therapies, is warranted.