Abstract PS6-05: Impact of body mass index on pathological complete response after neoadjuvant chemotherapy: Results from the I-SPY 2 trial

Purpose: Increased body mass index (BMI) is a risk factor for breast cancer and has been associated with poor outcomes in both premenopausal and postmenopausal breast cancer patients. Several retrospective studies have demonstrated higher BMI to be associated with inferior pathological complete response (pCR) to neoadjuvant chemotherapy, yet it remains unclear if this difference is related to chemotherapy underdosing among obese breast cancer patients. We evaluated the association between BMI and response to neoadjuvant chemotherapy (defined by pCR) in the I-SPY 2 trial, an adaptive clinical trial platform enrolling biologically high-risk breast cancer patients (triple negative, human epidermal growth factor receptor 2 (HER2) positive and MammaPrint high-risk) that utilizes standard neoadjuvant therapy regimens with treatment based on actual body weight. Patients and Methods: From 3/2010 to 11/2016, 989 patients were enrolled in the I-SPY 2 trial, 978 had a recorded baseline BMI prior to treatment and were included in the analysis. Tumor subtypes were defined by hormone receptor and HER2 status. Pretreatment BMI was categorized as obese (BMI>=30 kg/m2), overweight (25= Results: The median age in our study population was 49 years. 35% of patients were normal/underweight, 32% overweight, and 33% obese. Black patients were more likely to be obese (P Conclusions: There was no difference in pCR rates by BMI with actual body weight based neoadjuvant chemotherapy in this biologically high-risk breast cancer population. In contrast, breast cancer subtype and stage showed predictive value for pCR in this high-risk operable breast cancer population receiving neoadjuvant chemotherapy in the I-SPY 2 clinical trial. Citation Format: Haiyun Wang, Douglas Yee, David Potter, Patricia Jewett, Christina Yau, Heather Beckwith, Allison Watson, Nicholas G O9Grady, Amy Wilson, Susie Brain, I-SPY 2 TRIAL Consortium, Anne Blaes. Impact of body mass index on pathological complete response after neoadjuvant chemotherapy: Results from the I-SPY 2 trial [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS6-05.