Impact of body mass index on the pathological complete response among women with non-metastatic breast cancer treated with neoadjuvant chemotherapy in a tertiary cancer center in northern India.

e12627 Background: Late-stage presentation and locally advanced breast cancer forms a significant proportion of breast cancer (BC) burden in the India. Neoadjuvant chemotherapy (NACT) is the standard of care for such patients, is widely used for early breast cancer patients also. The impact of body mass index (BMI) on the NACT response among Indian women with BC is largely unknown. Methods: Demographic, baseline weight, height, clinical and tumor characteristics, were retrieved from the medical records of women who received NACT between years 2013-2024. Primary outcome was pathological complete response (PCR), defined as the absence of residual invasive and in situ cancer in the resected breast specimen and all sampled regional lymph nodes following completion of NACT (i.e., ypT0 ypN0). Logistic regression analysis was used to examine the association of BMI with PCR. Results: Study sample consisted of 557 women with non-metastatic BC who received NACT. Median age of the study cohort was 45years and 60% were premenopausal. Forty-three percent of the cases were Hormone receptor (HR) positive and Her2Neu negative, followed by 31.7% (HR+ and Her2Neu+), 18.4% (TNBC) and 7.0% (HR- and Her2Neu+). AJCC-Stage II tumors consisted of 28.7%, followed by 71.3% Stage-III. Forty-one percent were obese (BMI > 27.5kg/m 2 ) and 33.9% were overweight (BMI: 23-27.5kg/m 2 ). Fifty percent of postmenopausal women were obese at time of presentation compared to 34.5% of premenopausal women (p < 0.001). Proportions of those with one or more comorbidity were significantly high among obese group compared to other BMI categories (p < 0.001). Family history of cancer, clinical stage, HR/Her2Neu receptor status, ECOG score and type of surgery received did not vary across the BMI categories. PCR rate was 26.8% for the overall sample. Normal/Underweight individuals had higher PCR rate 32.1%, compared to overweight (25.1%) and obese (24.9%), however, this difference was not statistically significant (p = 0.267). Univariate [HR(95%CI): Overweight 0.71(0.44-1.16), Obese 0.70(0.44-1.12)] and multivariate logistic regression analysis adjusting for receptor status, stage, ECOG score and menopausal status showed that BMI has no effect on PCR [aHR(95%CI): Overweight 0.67(0.38-1.20), Obese 0.73(0.41-1.29)]. ECOG score ≥1 and Stage III tumors were associated with significantly less odds of PCR. HER2neu enriched and triple-negative subtypes of breast cancer had higher odds of PCR compared to HR+ tumors. Conclusions: This retrospective study showed that BMI has no impact on PCR rate following NACT among Indian women with non-metastatic BC. Further research focusing on the interactive effect of BMI on NACT response across various BC subtypes among BC patients is needed to guide treatment decisions and use of multimodal therapeutic approaches.