Geographic disparities in adherence to adjuvant endocrine therapy in Appalachian women with breast cancer

Abstract

Background: Appalachia is a largely rural, mountainous, poor and underserved region of the United States. Adherence to adjuvant endocrine therapy among Appalachian women with breast cancer is suboptimal.

Objectives: To explore small-area geographic variations and clustering patterns of breast cancer patient adherence to adjuvant endocrine therapy and associated factors in Appalachia.

Methods: In this retrospective study, we analyzed Medicare claims data linked with cancer registries from four Appalachian states (PA, OH, KY, and NC) in 2006-2008. We included adult women who were diagnosed with stage I-III, hormone-receptor positive, primary breast cancer and who newly started adjuvant endocrine therapy after the primary treatment for breast cancer. Hot spot analysis was conducted to explore geographic variations in adjuvant endocrine therapy adherence. Geographically weighted logistic regression (GWLR) was used to examine whether the impacts of factors associated with adherence varied across the region.

Results: Breast cancer patients living in PA and OH showed higher adherence to adjuvant endocrine therapy than those living in KY and NC. We identified clusters of high adherence in most of PA but poor adherence in Erie County, PA and in Buncombe, Transylvania, Henderson, and Polk Counties, NC. Adherence to adjuvant endocrine therapy was significantly associated with the Health Professional Shortage Area designation, catastrophic coverage, dual-eligibility status of Medicaid and Medicare, adjuvant endocrine therapy drug class, and side effects. And among these factors, the impacts of dual-eligibility status and the use of pain medications to treat side effects on adherence were more pronounced in KY and NC than in PA.

Conclusions: There were significant geographic disparities in adherence to adjuvant endocrine therapy in the Appalachian counties in PA, OH, KY, and NC. This study explored these geographic areas with poor adherence as well as geographically varying effects of predictors on adherence; our results may provide more localized information that may be used to improve adjuvant therapy use and breast cancer care in these high-risk and underserved areas.

Keywords: Adherence; Adjuvant endocrine therapy; Appalachia; Breast cancer; Geographically weighted regression.