Association of body mass index with pathological complete response after neoadjuvant chemotherapy in a population-based cohort of Black breast cancer patients

Purpose: Pathologic complete response (pCR) to neoadjuvant chemotherapy is associated with improved event-free and distant recurrence free survival in women with stage II or III breast cancer (BC). While there is strong evidence that obesity is associated with reduced BC survival, its role on pCR after neoadjuvant chemotherapy among BC patients is unclear. Moreover, data regarding the association of pre-treatment BMI with response to neoadjuvant chemotherapy in Black women – who have the highest obesity prevalence than any other racial/ethnic groups and 40% worse survival outcomes compared to White women – are lacking. The purpose of this study was to examine the association of pretreatment BMI and subsequent pCR after neoadjuvant chemotherapy in Black BC patients. Methods: Data were abstracted from medical records of 131 Black BC patients who received neoadjuvant chemotherapy in the Women9s Circle of Health Follow-up Study, a population-based cohort study of Black BC survivors in New Jersey. pCR was defined as absence of detectable invasive cancer in the breast and lymph nodes (ypT0/Tisand ypN0) at the time of surgery (noninvasive residual BC, i.e. DCIS was allowed). Tumor subtypes were defined by hormone receptor (HR, i.e., ER, PR) and HER2 status. Multivariable logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CIs) of the association between pretreatment obesity (BMI ≥30 kg/m²)vs. non-obese (<30 kg/m²), and pCR, after adjusting for covariates. The association with BMI in a continuous scale was also evaluated. Results: Mean age at BC diagnosis was 50±10.7 years, mean BMI was 31.4±7.1 kg/m², and 69 (52.7%) women were obese. In terms of tumor subtype, 53 (40.5%) were HR+/HER2-, 40 (30.5%) were HER2+, and 38 (29.0%) were triple negative. All patients received standard chemotherapy regimens and 8.4% of patients had dose reductions due to toxicity. Almost one-third achieved pCR (38 [29.0%]). Consistent with prior evidence, our findings were suggestive of decreased odds of pCR among obese (OR 0.88, 95% CI: 0.39-1.99) compared to non-obese women, although the risk estimate was not statistically significant. We observed similar findings with BMI modeled as a continuous variable (OR 0.85, 95% CI: 0.62-1.15 per 5-unit increase in BMI). No substantive differences were observed by tumor subtype (HR+/HER2: OR 0.80, 95% CI: 0.44-1.46; HER2+: OR 0.93, 95% CI: 0.58-1.47; and triple negative BC: OR 0.86, 95% CI: 0.47-1.57 per 5-unit increase in BMI). Conclusion: Our findings suggest that among Black women, higher BMI is inversely associated with achieving pCR. However, risk estimates did not reach statistical significance, possibly due to small sample size. Alternatively, as shown by our and others9 prior work, BMI may be an inadequate measure of adiposity, particularly in this population. Future work should evaluate the impact of body fat distribution and body composition on pCR response to neoadjuvant chemotherapy among Black women after a breast cancer diagnosis. Citation Format: Coral Omene, Saber Amin, Nur Zeinomar, Bo Qin, Dhanya Chanumolu, Adana A.M. Llanos, Chi-Chen Hong, Kitaw Demissie, Elisa V. Bandera. Association of body mass index with pathological complete response after neoadjuvant chemotherapy in a population-based cohort of Black breast cancer patients [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-119.