Body mass index and weight changes in patients with HER2-positive early breast cancer: A sub-analysis of the APHINITY trial

We assessed the association of BMI and weight changes with outcomes of patients with HER2-positive early BC included in the APHINITY trial. This is an exploratory analysis of APHINITY (NCT01358877), randomized trial testing adjuvant dual vs. single HER2 blockade plus chemotherapy in HER2-positive early BC. Of 4787 patients included, 2252 (47 %) were overweight/obese and 2535 (53 %) underweight/normal weight. Patients who were overweight/obese had more often chemotherapy discontinuation compared to underweight/normal weight patients (14 % vs. 9 %, p < 0.001). Patients who were overweight/obese exhibited worse iDFS (adjusted hazard ratio [aHR] 1.27; 95 %, DFRI (aHR 1.32; 95 %) and OS (aHR 1.38; 95 %) than underweight/normal weight patients. This effect on iDFS remained after adjusting for chemotherapy discontinuation (iDFS aHR 1.26, 95 %; DRFI aHR 1.31, 95 %; OS aHR 1.35 95 %). Weight changes at 2 years were not associated with clinical outcomes. Our exploratory findings suggest that overweight/obesity at diagnosis was associated with worse survival outcomes.