Abstract 4836: Race differences in symptom burden and medication adherence among women with breast cancer on adjuvant endocrine therapy: A post hoc analysis of a randomized control trial

Abstract Background: Adjuvant endocrine therapy (AET) reduces breast cancer recurrence, but racial differences in nonadherence remains a concern. Differential symptom burden may contribute to disparities in AET adherence. Method: We conducted a post hoc analysis by race among women with breast cancer starting AET who were randomized in THRIVE Study (NCT03592771) to investigate remote symptom monitoring intervention vs. usual care from 11/2018 to 06/2021. Participants completed surveys at baseline, 6- and 12-month. Outcomes were symptom burden measured by FACT-Endocrine Subscale, and adherence measured by electronically monitored pillbox (>80% Proportion of Days Covered). We estimated symptom differences by race using linear regression with and without adjusting for baseline characteristics. To examine whether symptom burden contributed to racial differences in adherence, we conducted multivariable regression for adherence with and without controlling for symptom burden, and Blinder-Oaxaca decomposition. Results: Among 102 (34%) Black and 194 (66%) White women who were randomized, retention was 88% at 12-month. Compared to White participants, Black participants were younger (55 vs. 60 years), more likely to be at poverty (10.8% vs. 4.1%), and had lower health literacy (18.9% vs. 13.4%; p-values<.01). While symptom burden did not differ by study arm, Black participants had worse symptoms than White at baseline (60.8 vs. 64.5, p=.002). This gap became smaller at 6-month (59.7 vs. 61.2, p=.30), but diverged again at 12-month (56.9 vs. 61.8, p<0.01). Differences at 12-month diminished after controlling for baseline characteristics (-1.6, 95%CI=-4.4 to 1.2). Notably, being at poverty and younger age were associated with higher symptoms. Adherence was lower among Black participants at 6-month (0.69 vs. 0.78, p=.13) and 12-month (0.44 vs. 0.60, p=.014) than White participants. Unadjusted differences in adherence at 12-month (-16.0 percentage points [ppts], 95%CI=-28.9 to -3.3, p=.01) attenuated after adjusting for baseline symptoms, symptom changes to 12-month, and other baseline characteristics (-10.4 ppts, 95%CI=-25.6 to 4.8, p=.18). Lower baseline symptoms were associated with better adherence (0.8 ppts, 95%CI=0.1 to 1.4, p=.03). Decomposition indicates that 9.1 ppts (95%CI=-4.8 to 23.0, 57%) of the difference in 12-month adherence was explained by symptoms and baseline characteristics, and remaining unexplained difference was 6.9 ppts (95%CI=-12.6 to 26.4, 43%). Conclusion: Our results add to increasing evidence that Black women with breast cancer have lower AET adherence, which may be partially attributed to worse symptoms than White women. These results highlight the need for new strategies to promote equitable symptom management and adherence strategies between Black and White women to reduce disparities in outcomes. Citation Format: Xin Hu, Rebecca A. Krukowski, Ed Stepanski, Lee S. Schwartzberg, Gregory A. Vidal, Ilana Graetz. Race differences in symptom burden and medication adherence among women with breast cancer on adjuvant endocrine therapy: A post hoc analysis of a randomized control trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4836.