Geographic disparities in adherence to adjuvant endocrine therapy in Appalachian women with breast cancer
Introduction
Adjuvant endocrine therapy (AET) is an important treatment modality for hormone-receptor (HR) positive breast cancer due to its significant benefits in reducing recurrence and mortality.1, 2, 3, 4 To achieve the optimal clinical benefits, adherence to AET is crucial.5, 6, 7 The current literature has identified many individual characteristics that may be inversely related to AET adherence such as extreme age (younger [under 40–45 years old] or older [over 75–85 years old]), higher out-of-pocket drug costs, switching drugs, drug class (aromatase inhibitors vs. tamoxifen), suboptimal patient-centered communication, lack of perceived self-efficacy in patient–physician interaction, and adverse drug reactions,5, 8, 9, 10, 11 but the literature has paid limited attention to geography or associated factors. In fact, geography can serve as a proxy or composite measure for various observed and unobserved variables that may be related to medication adherence, such as access to care, available health resources, socioeconomic status, disease burden, race/ethnicity, and culture.12 Examining geography and associated factors may help advance AET adherence research by further explaining individual variations in AET adherence that cannot be fully explained by individual characteristics. Small-area geographic variations in medication adherence may be attributable to the neighborhood effect, which describes the social interactions impacting an individual's behavior or outcomes.13 Theoretically, people residing in the same neighborhood are more likely to share common social norms, cultural background, socioeconomic status, and systemic and lifestyle characteristics compared to people living in different neighborhoods, which may further shape health behaviors, including medication-taking behaviors, above the individual-level.14 There may also be provider neighborhood effects, such as possible ineffective or inadequate patient-provider communication in the Health Professional Shortage Area (HPSA) that leads to the failure to underscore the importance of AET adherence, or similar prescribing or practice behaviors under the influence of similar policies, regulations or interventions in one area.
The Appalachian region of the United States (US) covers 204,452 square miles in 420 counties along the spine of the Appalachian Mountains.15 This region contains all of West Virginia, and portions of 12 other states: New York, Pennsylvania, Ohio, Maryland, Kentucky, Virginia, Tennessee, North Carolina, South Carolina, Georgia, Alabama, and Mississippi. The Appalachian population in the US is a special population of interest in cancer research because it consistently suffers from a significant cancer burden, with higher cancer incidence and mortality than the non-Appalachian population.16, 17 In terms of breast cancer, compared to other regions, Appalachia experienced a slower decline in breast cancer mortality,18 and its patients receive guideline-recommended breast cancer screening and primary treatment at lower rates than those in other regions.19, 20, 21 The factors leading to poor access to and utilization of care in this region may include rural residence, geographic isolation, lack of public transportation, underdeveloped telecommunication infrastructure, high poverty and unemployment rates, inadequate medical resources, a shortage of healthcare professionals, lower levels of educational attainment, and attitudinal and cultural factors.20, 22, 23 Given the largely rural, mountainous environment and unsatisfactory patient adherence to AET in Appalachia as a whole,5 we need to measure geographic variations in AET adherence beyond the general urban and rural classification. The identification of “hot spots” that require monitoring and intervention can help local communities to develop strategies to improve cancer treatment use and outcomes. However, there have been very few studies examining geographic disparities in adjuvant cancer treatment use in this region, primarily due to the lack of data and of a representative study sample. Therefore, we pursued the following study aims: 1) to explore small-area geographic variations and clustering patterns of AET adherence; and 2) to examine spatial non-stationarity of the relationships between potential predictors and AET adherence.
Section snippets
Study design and study population
In this retrospective study, we analyzed Medicare claims data linked with cancer registries from four Appalachian states (PA, OH, KY, and NC) between January 1, 2006 and December 31, 2008. We only assessed the Appalachian counties in these four states, not including the non-Appalachian counties. The study design included a baseline period that began one year before the diagnosis date, and patients were followed from the date of the first AET prescription until death or until the end of the
Results
A total of 428 eligible women with an average age of 74.8 years old were included in the study. Table 1shows the basic characteristics of the study sample. The MPR values ranged from 0.06 to 1.20, with a mean of 0.83 and a standard deviation (SD) of 0.24. Only about 69.4% of the population were adherent to AET. Significant bivariate predictors of MPR >0.80 at α = 0.05 included having dual status (65.8% yes vs. 78.5% no), having catastrophic coverage (82.3% yes vs. 64.8 no), positive lymph nodes
Discussion
Patient adherence to AET is essential to maximize its significant benefits in cancer outcomes for HR-positive breast cancer survivors; therefore disparities in AET adherence may partly contribute to the disparities in breast cancer outcomes including mortality. Appalachia has experienced substantial cancer disparities over the years. In this study, we used innovative geographic analytic tools and a unique dataset linking Medicare claims with cancer registries from four Appalachian states (PA,
Conclusions
This study is among the first to demonstrate the utility and feasibility of using geographic techniques as a tool to account for geographic variations and neighborhood effects on medication adherence and its predictors in a specified region. It explored specific geographic areas in Appalachia with poor AET adherence as well as geographically varying effects of predictors on AET adherence, which may help direct future research, policy, and interventions to focus on these high-risk areas and
Acknowledgment
This study was funded by the National Cancer Institute (NCI) (Grant R21 CA168479) and the National Institutes of Health (NIH) office of Women's Health (Grant: 1 R21 CA168479; PI: Balkrishnan).
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