OBJECTIVES : Recent studies have documented both issues with access to adjuvant androgen deprivation therapy (ADT) and side effects associated with these treatments. However, none of these studies examine the role of medication adherence which could be a key driving factor in treatment success. We explored medication use patterns associated with the for up to a 2 year post-start date period in Medicare-enrolled prostate cancer survivors using the National Comprehensive Cancer Network (NCCN) guidelines for ADT therapy in prostate cancer.

METHODS : Using SEER (Surveillance, Epidemiology, and End Results Program)-Medicare linked data from 2007 to 2012 we identified a cohort of 5,064 enrollees with Medicare Part D coverage (nearly three quarters diagnosed with Stage II tumor) who began adjuvant ADT therapy, of which 3,407 (67.3%) discontinued treatment after an initial period of 90 days. Amongst the 5,064 patients who used ADT treatment, a total of 784 (15.5%) and 337 (6.7%) patients used the treatment at least 80 percent of time using the proportion of days covered (PDC) measure and were classified as adherent for the 1 year and 2 year period respectively.

RESULTS : Using multivariate Cox proportional hazards multivariate models, we found that ADT non-adherent patients had an increased risk of mortality for Year 2 but not Year 1 (Hazard Ratio: 1.002 (95% CI: 0.82-1.21) for Year 1 and Hazard Ratio: 1.90 (95% CI: 1.38-2.62) for Year 2). Other factors independently associated with increased all-cause mortality hazard in elderly prostate cancer survivors included increased age, greater comorbidity, advanced stage, and being unmarried

CONCLUSIONS : There is a clear association between increased adherence to ADT therapy and decreased all-cause mortality in elderly Medicare enrollees with prostate cancer. This effect is independent of the stage of cancer and health status of the patient. Future research needs to examine long-term outcomes associated with ADT use in high mortality risk populations.