Real-world (RW) analysis of characteristics and risk of recurrence (ROR) in Black patients (pts) with HR+/HER2− early breast cancer (EBC) eligible for NATALEE.

527 Background: The NATALEE trial showed statistically significant and clinically meaningful invasive disease–free survival benefit with ribociclib + nonsteroidal aromatase inhibitor (NSAI) vs NSAI alone in pts with stage II/III HR+/HER2− EBC at high ROR that deepened even after all pts were off ribociclib. Prior RW analyses have shown clinically meaningful ROR at 5 y despite endocrine therapy (ET) among NATALEE-eligible pts. TAILORx and RxPONDER reported racial disparities in recurrence and outcomes; however, further understanding of characteristics and unmet needs in Black pts is needed. This RW analysis describes pt characteristics and outcomes among Black pts eligible for NATALEE and receiving ET. Methods: Data from the US Flatiron Health EHR-derived deidentified database (2011-2023) were used. Selection criteria included pts aged ≥18 y with anatomical stage I-III (AJCC) HR+/HER2− EBC who had primary tumor surgical resection and started adjuvant ET. Pt characteristics and treatment patterns were analyzed in Black vs White pts eligible for NATALEE. ET (any) adherence was defined as proportion of days covered ≥80%. Recurrence-free survival (RFS), distant recurrence–free survival (DRFS), and overall survival (OS) were assessed descriptively and using multivariate Cox regression analysis. Results: A total of7481 pts met selection criteria. Overall, 41.2% (242/588) of Black and 33.0% (1697/5142) of White pts met NATALEE eligibility criteria. Compared with White pts, Black pts were younger (median age, 59 y vs 62 y) and more likely to be premenopausal (29.3% vs 23.8%), have anatomical stage III disease (35.1% vs 25.7%), more extensive nodal involvement (19.8% N0, 54.1% N1, 14.0% N2, and 7.0% N3 vs 24.0% N0, 53.3% N1, 11.3% N2, and 6.2% N3), higher use of Medicaid (13.2% vs 3.6%), lower socioeconomic status (lowest socioeconomic status quintile, 33.9% vs 11.4%), higher obesity (body mass index ≥30, 52.9% vs 38.4%), and lower ET adherence (3 y ET adherence: 57.0% vs 65.2%; 5 y ET adherence: 48.3% vs 56.2%). Five-y RFS, DRFS, and OS rates were 74.3%, 77.6%, and 85.0%, respectively, in Black pts and 83.2%, 84.5%, and 90.9% in White pts. Compared to White pts, Black pts had worse RFS (hazard ratio, 1.5; P =0.0045), DRFS (hazard ratio, 1.4; P =0.0272), and OS (hazard ratio, 1.7; P =0.0023) after adjusting for age, menopausal status, body mass index, tumor size and grade, nodal status, chemotherapy use, and socioeconomic status index. Conclusions: In a RW dataset of pts eligible for adjuvant ribociclib based on NATALEE inclusion criteria, Black pts had a higher recurrence risk and worse survival compared with White pts, underscoring the opportunity to improve outcomes and address racial disparities in Black pts with HR+/HER2− EBC.