Abstract
BackgroundThere are racial/ethnic disparities in breast cancer mortality may be attributed to differences in receipt of adjuvant cancer treatment. Our purpose was to determine whether the mortality disparities could be explained by racial/ethnic differences in long-term adherence to adjuvant endocrine therapy (AET).MethodsWe conducted a retrospective cohort study with the Texas Cancer Registry and Medicaid claims-linked dataset of women (20-64 years) diagnosed with local and regional breast cancer who filled a prescription for AET from 2000-2008. Adherence to AET was measured at three time points (1-, 3-, and 5-year adherence) using a value for the percentage of medication filled for each period divided by the total number of possible prescriptions prescribed (Medication Possession Ratio, MPR). We created a binary variable of adherence (MPR≥80%). We performed multivariable logistic regressions to assess racial differences for the odds of AET adherence and Cox proportional hazard models to determine the risk of mortality adjusting for potential confounding variables of SES, comorbidities, tumor prognostic factors, and other cancer treatment.ResultsOf the 1,497 women with breast cancer who initiated AET, 56.9%, 42.3%, and 33.3% were adherent for 1, 3, and 5-years, respectively. Hispanics compared to non-Hispanic whites did differ in the proportion that were adherent to 5-years of AET. In the adjusted analysis for long-term adherence to AET, Hispanics did not have a significantly increased risk of death compared to non-Hispanic white patients (HR: 1.13, 95% CI: 0.58-2.21). However, black compared to non-Hispanic white patients had significantly lower odds of three-year adherence (OR: 0.45, 95% CI: 0.28-0.73). After controlling for 5-year adherence to AET, the risk of death for black compared to non-Hispanic white patients was 12% lower (HR: 1.90; 95% CI: 1.03-3.51) and in the fully adjusted model, the disparity was reduced and no longer significant (OR: 1.86, 95% CI: 0.94-3.66).ConclusionsLong-term adherence in the Medicaid population is suboptimal and racial/ethnic differences in AET adherence may partially explain disparities in mortality. This study underscores the critical need to ensure long-term adherence to AET for all racial/ethnic groups to decrease disparities in mortality.
Highlights
There are racial/ethnic disparities in breast cancer mortality may be attributed to differences in receipt of adjuvant cancer treatment
Adherence to recommended treatment, such as adjuvant endocrine therapy (AET), is one way to significantly reduce breast cancer mortality [7] since adherence to AET is associated with improved disease-free survival for women with early-stage breast cancer [8,9,10,11,12].racial/ethnic differences in adherence to AET may be a determinant that contributes to disparities in breast cancer outcomes [13]
20% of the patients diagnosed with breast cancer resided in a county along the Texas-Mexico border, 44% of all Hispanic breast cancer patients resided in the region compared to only 5.3% and 1.4% as Non-Hispanic White and Black, respectively
Summary
There are racial/ethnic disparities in breast cancer mortality may be attributed to differences in receipt of adjuvant cancer treatment. Minorities with breast cancer have an increased risk of breast cancer death than non-Hispanic whites [1,2,3,4] These racial/ethnic mortality disparities have been attributed to differences in factors such as tumor characteristics [2, 3, 5, 6], socioeconomic factors [4], and the initiation and timing of initial and adjuvant cancer treatment [2, 4]. Few studies have examined long-term adherence over the 5-year recommended period, which is important to receive the maximal disease-free survival benefit Studying these factors among across the entire 5-year duration of recommended treatment is critical for our understanding of AET adherence
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