Abstract PO4-03-06: Body mass index and response to neoadjuvant chemo-immunotherapy among women with primary triple negative breast cancer

Abstract Background: Elevated body mass index (BMI) is associated with lower rates of pathologic complete response (pCR) after neoadjuvant chemotherapy in patients with breast cancer. The addition of PD-1 receptor inhibition with pembrolizumab to neoadjuvant chemotherapy is now considered the standard of care for patients with stage II or III triple negative breast cancer (TNBC) based on results from the KEYNOTE-522 (KN-522) trial. In other cancer types such as melanoma and lung cancer, patients with overweight/obesity have better survival outcomes following treatment with immunotherapy compared to patients with normal weight, despite a higher incidence of any-grade immune-related adverse events (irAEs). Whether BMI is associated with differential response and toxicity in patients with TNBC treated with neoadjuvant chemo-immunotherapy is unknown. Methods: Patients with stage II-III TNBC treated with neoadjuvant chemotherapy plus pembrolizumab per the KN-522 regimen from 8/2021 – 9/2022 at Memorial Sloan Kettering Cancer Center were included in this retrospective study. Patient characteristics, tumor characteristics, treatments, surgical pathology information, and irAEs were abstracted from medical records. pCR was defined as absence of invasive or in situ carcinoma in breast and axillary node tissue surgical specimens. BMI was categorized per standard definitions: underweight/normal weight < 25 kg/m2, overweight 25-29.9 kg/m2, and obese >=30 kg/m2. Wilcoxon rank sum tests, Pearson’s chi-squared tests, and Kendall rank correlation tests were used to test associations between variables. Results: 143 patients were included in this study. 57 patients (39.8%) were underweight/normal weight, 46 (32.2%) were overweight, and 40 (28.0%) were obese. Overall, 79/143 patients (55.2%) experienced a pCR. Among patients with a pCR, median BMI was 26.3 kg/m2 (interquartile range [IQR] 23.1-30.5 kg/m2); among patients without a pCR, median BMI was 26.1 kg/m2 (IQR 23.6-30.0 kg/m2; p >0.9). There was no significant association between BMI category and pCR (p=0.9). Overall, 63/143 (44%) of patients experienced an irAE; 42 (29.4%) required treatment for an irAE. There were no associations between BMI and the incidence (p=0.5) or frequency (p=0.7) of irAEs. Conclusions: In this TNBC cohort treated with neoadjuvant chemo-immunotherapy, BMI was not associated with rates of pCR or irAEs. These findings highlight the divergent impact of BMI on immunotherapy response across cancer types. Confirmatory studies in independent cohorts are needed. Citation Format: Sherry Shen, Sara Myers, Yuan Chen, Stephanie Downs-Canner, Nour Abuhadra, Tiffany Traina, Mark Robson, Neil Iyengar. Body mass index and response to neoadjuvant chemo-immunotherapy among women with primary triple negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-03-06.