Impact Of Body Mass (Bmi) And Weight Change After Adjuvant Treatment In Patients (Pts) With Her2-Positive Early Breast Cancer

A better knowledge of the impact of BMI on prognosis and response to treatments is important to tailor treatment strategies and survivorship care. We assessed the impact of BMI at diagnosis and weight changes on outcomes of pts with HER2-positive early BC included in the APHINITY trial, who all received chemotherapy (ChT) plus single or dual HER2 blockade. Pts were classified as normal/underweight (BMI<25kg/m2) and overweight/obese (BMI≥25kg/m2). The impact of baseline BMI on invasive disease-free survival (IDFS) and distant recurrence-free interval (DRFI) was assessed. Multivariable analyses adjusting for baseline features that differed according to BMI (age, menopausal status, tumor size, type of endocrine therapy and ChT) were performed. A landmark analysis was done to study the impact of weight changes (5% loss or gain) at 2y. 4787 pts were included: 2535 (53%) were normal/underweight and 2252 (47%) overweight/obese. BMI≥25 at baseline was associated with older age, postmenopausal status, larger tumours, less treatment with anthracyclines and more use of aromatase inhibitors. BMI≥25 was associated with worse IDFS (adjusted hazard ratio [aHR] 1.27; 95% CI 1.06-1.52) and DRFI (aHR 1.32; 95% CI 1.06-1.64). Subgroup analyses suggested a negative impact of BMI≥25 for pts with hormone receptor-negative BC (IDFS: aHR 1.52; 95% CI 1.14-2.03; DRFI: aHR 1.57; 95% CI 1.10-2.24), postmenopausal (IDFS aHR:1.30; 95% CI 1.01-1.68; DRFI: aHR 1.37; 95% CI 1.00-1.89), pts treated with dual HER2-blockade (IDFS: aHR 1.47; 95% CI 1.12-1.93; DRFI: aHR 1.51; 95% CI 1.09-2.11), and anthracyclines (IDFS: aHR 1.26; 95% CI 1.03-1.54; DRFI: aHR 1.34; 95% CI 1.05-1.70). Weight changes did not impact on IDFS (n=3961)-Loss aHR 1.03, 95% CI 0.71-1.50; Gain aHR 1.00; 95% CI 0.76-1.31 or DRFI (n=3965)-Loss aHR 0.93, 95% CI 0.59-1.47; Gain aHR 0.90; 95% CI 0.64-1.26. Analysis with 4 BMI categories did not profoundly change the conclusions (data will be presented). In this exploratory analysis, BMI≥25 at baseline appeared to be associated with inferior IDFS and DRFI in pts with HER2-positive early BC. Further research assessing the impact of weight changes on IDFS and DRFI is needed to better inform survivorship programs.