Racial and ethnic differences in breast-conserving surgery after neoadjuvant chemotherapy for HER2-positive and triple-negative breast cancer.

e13724 Background: Neoadjuvant chemotherapy (NACT) increases eligibility for breast-conserving surgery (BCS) among patients with stage II–III breast cancer, particularly those with HER2-positive and triple-negative breast cancer (TNBC). Despite equivalent oncologic outcomes between BCS and mastectomy, racial and ethnic disparities in surgical management persist. Data examining racial and ethnic differences in receipt of BCS following NACT remains limited. We examined the association between race and ethnicity and the odds of undergoing BCS after NACT. Methods: The National Cancer Database was used to identify female patients with stage II or III HER2-positive or triple-negative breast cancer diagnosed between 2013 to 2022 who received NACT followed by surgery. Patients were categorized by race and ethnicity, and the primary outcome was receipt of BCS versus mastectomy. Demographic, clinical, and treatment variables were compared using Chi-square tests and one-way ANOVA, as appropriate. Multivariable logistic regression was used to examine the association between race/ ethnicity and the odds of undergoing BCS, adjusting for age, year of diagnosis, clinical stage, subtype, insurance status, geographic region, facility type, and comorbidity score. Odds ratios with 95% confidence intervals were reported. Results: Among 255,735 women who met inclusion criteria, 65.4% were non-Hispanic White, 19.5% Black, 9.3% Hispanic, 5.3% Asian or Pacific Islander, and 0.4% American Indian or Alaskan Native. The cohort included 65.3% with stage II disease and 34.7% with stage III; 66.7% had TNBC and 33.3% HER2-positive disease. Following NACT, 60.1% underwent mastectomy and 39.9% underwent BCS. Compared with Non-Hispanic White women, Black (OR 1.26, 95% CI 1.15-1.38) and Hispanic (OR 1.23, 95% CI 1.04-1.46) women had higher odds of receiving BCS, whereas Asian and Pacific Islanders had lower odds (OR 0.73, 95% CI 0.56-0.94) (Table 1). Older age, stage II disease, lower comorbidity score, treatment in New England, and more recent diagnosis year were independently associated with significantly higher odds of receiving BCS. On moderation analysis, clinical stage did not modify the association between race/ ethnicity and receipt of BCS. Conclusions: Patterns of surgical management following NACT vary by race and ethnicity. Black and Hispanic women had higher odds of undergoing BCS compared with Non-Hispanic White women, whereas Asian and Pacific Islander women had lower odds, independent of key covariates. Further research is needed to elucidate the underlying factors contributing to these differences. BCS Adjusted OR (95% CI) p-value Race/ Ethnicity: Non-Hispanic White Reference Black 1.26 (1.15 - 1.38) <0.001 Asian or Pacific Islander 0.73 (0.56 - 0.94) 0.016 American Indian or Alaskan Native 0.81 (0.60 - 1.09) 0.169 Hispanic 1.24 (1.04 - 1.46) 0.016