There is a paucity of literature systemically examining the effects of access to
cancer care resources on adjuvant endocrine
therapy (
AET) use behaviors, especially in underserved regions such as the Appalachian region in the United States, where gaps in healthcare access are well documented. The objectives of this study were to explore
AET adherence and persistence in Appalachia, delineate the effects of access to care
cancer on adherence/persistence, and evaluate the influences of adherence and persistence on overall survival.A retrospective cohort study from 2006 to 2008 was conducted among female
breast cancer survivors living in the Appalachian counties of 4 states (PA,
OH, KY, and NC). We linked
cancer registries to Medicare claims data and included patients with invasive, nonmetastatic,
hormone-receptor-positive
breast cancer who received guideline-recommended
AET. Medication adherence was defined as corresponding to a Medication Possession Ratio (MPR) ≥0.8 and logistic regression was utilized to assess predictors of adherence. Medication nonpersistence was defined as the discontinuation of drugs after exceeding a 60-day medication gap, and multivariate adjusted estimates of nonpersistence were obtained using the Cox proportional hazards (PH) model.About 31% of the total 428 patients were not adherent to
AET, and 30% were not persistent over an average follow-up period of 421 days.
Tamoxifen, relative to
aromatase inhibitors, was associated with higher odds of adherence (odds ratio = 2.82, P < 0.001) and a lower risk of nonpersistence (hazard ratio = 0.40, P < 0.001).
Drug-related side effects like
pain may be an important factor leading to nonadherence and early discontinuation. In addition,
aromatase inhibitor (AI) adherence and persistence were significantly influenced by out-of-pocket drug costs, dual eligibility status, and coverage gaps. Nonadherence to and nonpersistence with
AET were associated with higher risks of all-cause mortality.Our findings of suboptimal
AET adherence/persistence in Appalachia as well as positive associations between
AET adherence/persistence and overall survival outcomes further underscore the importance of ensuring appropriate
AET use in this population to reduce
breast cancer mortality disparities. Our findings also suggest that intervention strategies focusing on individualized treatment and medication-related factors may improve adjuvant treatment use.