Abstract B141: Predictors of prescription and self-reported use of endocrine therapy among hormone receptor positive breast cancer survivors in the Detroit Research on Cancer Survivors cohort
Authors: Purrington Kristen S. , Assad Hadeel , Ruterbusch Julie J. , Schwartz Ann G. , Kim Seongho , Hamel Lauren 
Published: December 2023

Abstract
Black women with hormone receptor (HR) positive (+) breast cancer are twice as likely to have weakly HR+ tumors (1-10% of tumor cells staining positive for HR) compared to White women, and women with weakly HR+ tumors are 60% more likely to die from their breast cancer compared to those with strongly HR+ tumors (&gt;10% of tumor cells staining positive for HR). While all women with HR+ breast cancer are recommended to receive endocrine therapy (ET) regardless of the strength of HR positivity, we have also shown that women with weakly HR+ tumors are 20% less likely to receive ET compared to women with strongly HR+ tumors. The goal of this analysis was to better understand the multi-level factors associated with prescription and self-reported use of ET among Black women with HR+ breast cancer. We used questionnaire data from 922 Detroit Research on Cancer Survivors (ROCS) participants with HR+ breast cancer to evaluate demographics, socioeconomic status, health status, tumor characteristics, treatment, treating oncologist characteristics, and treating hospital characteristics as predictors of oncologists’ intent to prescribe ET as well as self-reported use of ET. Intent to prescribe ET was defined as any evidence of ET prescription regardless of whether patients refused or had contraindications. Odds ratios were calculated using mixed-effects logistic regression models to account for group-level oncologist and hospital effects in single and multivariable analyses. Oncologists intended to prescribe ET for 83.4% (n=769) of participants, and 30.2% (n=232) of these participants reported ever having received ET to treat their breast cancer. Accounting for 6.7% of participants, patients with weakly HR+ tumors were 16-fold (p&lt;0.001) more likely to be prescribed ET in the multivariable model. Other significant predictors included BMI of less than 25 kg/m2 (OR=2.12, p=0.0053) or at least 30 kg/m2 (OR=2.39, p=0.032) compared to BMI &lt;25 kg/m2, &gt;10% HR vs. 1-10% HR (OR=2.19, p=0.0056), having an OncotypeDx test performed (OR=2.19, p=0.0056), and receiving radiation (OR=2.27, p=0.0015). Among participants who were prescribed ET, self-reported use of ET was associated with more recent year of diagnosis (OR=1.34, p&lt;0.001), completing at least a high school education (OR=2.87, p=0.025), higher health literacy (OR=1.27, p=0.013), distant stage at diagnosis (OR=3.16, p=0.041), and not having undergone surgery (OR=9.54, p=&lt;0.001). While physician- and hospital-characteristics such as oncologist gender and hospital size were associated with ET use and prescription in single variables models, these did not remain significant in multivariable models. We will continue to explore factors associated with longitudinal ET adherence using data from yearly follow-up questionnaires. Identification of the distinct sets of clinical and patient-level factors associated with prescription versus self-reported use of ET will help to inform the development of multilevel interventions to increase uptake of ET and ultimately improve survival among Black women with HR+ breast cancer.
Citation Format: Kristen S. Purrington, Hadeel Assad, Julie J. Ruterbusch, Ann G. Schwartz, Seongho Kim, Lauren Hamel. Predictors of prescription and self-reported use of endocrine therapy among hormone receptor positive breast cancer survivors in the Detroit Research on Cancer Survivors cohort [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr B141.