Background: Breast cancer treatment includes neoadjuvant chemotherapy (NAC), offered to patients with locally advanced breast cancer and who may benefit from down-staging before conservation therapy. NAC allows for evaluation of treatment response with pathologic complete response (pCR) acting as a marker of survival. Black women receive NAC more frequently as they often present with more advanced stage tumors and the triple negative subtype. Furthermore, Black women without pCR following NAC are at greater risk of mortality. Obesity is a prognostic factor for breast cancer. Non-Hispanic Black women have the greatest prevalence of obesity in most states. Patients with higher Body Mass Index (BMI) have previously been shown to have lower rates of chemotherapy response. Data on racial and ethnic differences in pCR rates are limited and whether obesity is a confounding factor requires investigation. Methods: Retrospective review of patients diagnosed with non-metastatic breast cancer who completed NAC and had surgery at Ohio State University James Comprehensive Cancer Center between January 1, 2005, and December 31, 2019, were analyzed. Clinical stage was calculated based on tumor size and nodal status. Operative treatment received was recorded to determine pathologic stage and chemotherapy response. The study endpoint, pCR, was assessed after definitive surgery. BMI categories were based on World Health Organization classification and obese defined as 30kg/m2. For the data analysis, we included self-reported Black and White women, excluding patients classified as “Other” race. Preliminary analyses included the distribution of sample descriptive characteristics. Differences by race and demographic characteristics were compared using Pearson’s chi-square test for categorical variables and t-test or Wilcoxon rank-sum test for continuous variables. Univariate analysis and multivariable logistic regression for pCR by age, race, BMI, menopausal status, insurance status and employment status were performed. Results: A final sample of 882 met criteria (11.7% Black and 88.3% white women, 1% Hispanic ethnicity). Median age of diagnosis is 51, with median 147.4 months of follow-up. 64% of the sample had clinical stage 2 disease, 22% were triple negative, 62% Her-2 positive subtypes. For tumor characteristics 67% of Black women and 59% white women had high grade tumor. Black women also had more triple negative disease (30% vs. 21%), more advanced stage at presentation (27% vs. 21%). More white women were employed and had private insurance compared to Black women, who predominantly had public insurance. The median BMI was higher among Black women (31.5) than white women (28.6). 52% of white women vs. 47% Black had mastectomy over lumpectomy. 67% of white women had radiation vs. 61% of Black women. Overall, 33% of Black and white women had pCR, with 67% having no pCR. Race and BMI were not significant predictors of PCR rates on univariate or multivariable analysis. Age < 40 is the only variable associated with pCR (OR 1.645, [95 CI 1.117-2.420] p-value: 0.012). Conclusions: BMI was not a significant predictor of pCR in this limited retrospective review. However, further exploration with a larger sample evaluating differences in pCR by BMI can lead to a better understanding of the association between obesity and pCR. Though race was not significant in predicting pCR, there is also room for further research considering socioeconomic disparities and obesity rates by race. Table 1. Table 1. Predictors for pCR. Table 1. Multivariable logistic regression for pCR adjusted by age, race, BMI, menopause status, insurance status, employment status. Univariate analysis for predictors of pCR performed for race and BMI. Citation Format: Ruvarashe Rumano, Michael Grimm, Marilly Palettas, Julie Stephens, Nicole Williams, Sagar Sardesai, Dionisia Quiroga, Bhuvaneswari Ramaswamy, Electra Paskett, Bridget Oppong. Differences in breast tumor response to neoadjuvant chemotherapy by race- Is obesity the key? [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-01-06.