Racial and Ethnic Disparities in Locoregional Recurrence Among Patients With Hormone Receptor–Positive, Node-Negative Breast Cancer

Importance: Whether racial and ethnic disparities in locoregional recurrence (LRR) exist among patients with similar access to care treated in randomized clinical trials is unknown. Objective: To examine racial and ethnic differences in LRR among patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (ERBB2 formerly HER2 or HER2/neu)-negative, node-negative breast cancer enrolled in the Trial Assigning Individualized Options for Treatment (TAILORx). Design, Setting, and Participants: This unplanned retrospective post hoc analysis examined a prospective multicenter clinical trial population of women with breast cancer enrolled between 2006 and 2010, with 9 years of follow-up. The TAILORx investigators randomized patients to treatment based on their Oncotype DX recurrence score, including endocrine therapy alone (recurrence score 25). Patients with unknown race and ethnicity or lack of follow-up were excluded from this analysis. Data analysis was performed between December 2021 and March 2022. Main Outcome and Measures: Locoregional recurrence was defined as ipsilateral in breast, skin, chest wall, or regional nodal recurrence without concurrent distant recurrence, and was stratified by racial and ethnic group. Unadjusted Kaplan-Meier and adjusted Cox proportional hazards regression models were used for survival analyses. Results: Of the 10 273 women enrolled in TAILORx, this analysis included 9369 with T1-2N0 HR-positive, ERBB2-negative breast cancer. Of these patients, 428 (4.6%) were Asian, 886 (9.4%) were Hispanic, 676 (7.2%) were non-Hispanic Black (hereinafter Black), and 7406 (78.8%) were non-Hispanic White (hereinafter White). Assigned treatment receipt was high, with a 9.3% (n = 870) crossover of treatment groups and a median endocrine therapy duration of longer than 60 months, ranging from 61.1 to 65.9 months, across racial and ethnic groups. A total of 6818 patients (72.6%) received radiation (6474 96.1% after breast-conserving surgery and 344 13.0% after mastectomy). At a median follow-up of 94.8 months (range, 1-138 months), 8-year LRR rates were 3.6% (95% CI, 1.6%-5.6%) in Asian patients, 3.9% (95% CI, 2.2%-5.4%) in Black patients, 3.1% in Hispanic patients (95% CI, 1.7%-4.5%), and 1.8% (95% CI, 1.5%-2.3%) in White patients (P < .001). In survival analyses adjusted for patient, tumor, and treatment factors, Asian race (hazard ratio, 1.91 95% CI, 1.12-3.29) and Black race (1.78 1.15-2.77) were independently associated with LRR. In adjusted survival analyses for breast cancer mortality, LRR was independently associated with increased breast cancer mortality (hazard ratio, 5.71 95% CI, 3.50-9.31). Conclusions and Relevance: In this post hoc analysis, racial and ethnic differences in LRR were observed among patients with T1-2N0 HR-positive, ERBB2-negative breast cancer despite high rates of treatment receipt in this clinical trial population, with the highest LRR rates in Asian and Black patients. Further study is needed to understand whether failure to rescue after LRR may contribute to racial disparities in breast cancer mortality. Trial Registration: ClinicalTrials.gov Identifier: NCT00310180.