Purpose: The effectiveness of adjuvant endocrine therapy (AET) to reduce morbidity and mortality among women diagnosed with hormone-receptor positive (HR+) breast cancer (BC) is well understood, yet the potential debilitating toxicities for Black survivors is not. Further, symptom toxicities impact treatment adherence.

Using a mixed methods approach, this study examined patterns of reported AET- related toxicities in HR+ Black and White survivors. Methods: Study participants were enrolled in the Women’s Hormonal Initiation and Persistence study, a longitudinal observational trial of women diagnosed with HR+ breast cancer. Data regarding patient (e.g. race), medication (e.g. AET type), cancer care delivery (e.g. communication), and clinicopathologic factors (e.g., chemotherapy) were collected via surveys and medical charts. The FACT-ES assessed AET toxicity at baseline, 12 and 24 months. Primary analyses focused on the first year; secondary analyses explored changes over time. Multivariable linear regression models examined predictors of AET overall toxicity and for 5 toxicity subgroups. Focus groups with women (N=30) prescribed AET were transcribed verbatim, coded and analyzed. Results: Of the 570 participants, 28% were Black. Black women were more likely to have chemotherapy prior to starting AET but as likely as whites to have radiation. Most women (62%) were taking aromatase inhibitors (AIs). In unadjusted analyses Black women reported more overall, vasomotor, neurological, and gastrointestinal toxicities (p<.05). Race was insignificant in multivariable analysis. Factors associated with higher AET toxicity were higher medication concerns (ß=1.29; CI: 0.88 – 1.69; p<0.001), younger age (ß=-0.23; CI: -0.36 – -0.10; p<0.001), and lower satisfaction with care (ß=-0.24; CI: -0.48 – 0.01; p=0.041). Higher AET gynecological toxicities were associated with AI use (vs. Tamoxifen) (p=0.002) Trends of toxicities over time suggest higher overall reporting by Black women (P=0.07). Qualitative analysis revealed that most women were not prepared for AET toxicities and desired more information at the start of AET. More often than Whites, Black women reported receipt of less information from providers and emphasized that spiritual coping supported their ability to adhere to AET therapy despite toxicities. Conclusion: During the first year of AET, racial disparities in toxicity diminished when controlling for psychosocial and communication factors. Development of interventions that target these factors may enhance symptom management, self-care, and potentially adherence.

Citation Format: Vanessa B. Sheppard, Arnethea L. Sutton, Reuben Retnam, Kandace P. McGuire. Treatment-related toxicities in Black and White women taking adjuvant endocrine therapy [abstract]. In: Proceedings of the AACR Virtual Conference: Thirteenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2020 Oct 2-4. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(12 Suppl):Abstract nr PO-097.