Weight Loss Patterns and Clinical Outcomes of GLP1 Receptor Agonists in Breast Cancer Survivors.

UNLABELLED: The use of glucagon-like peptide-1 receptor agonists (GLP1-RA) for weight loss is increasing; implications in breast cancer survivors remain unclear. This retrospective cohort study evaluated treatment patterns, weight loss, and outcomes in breast cancer survivors receiving GLP1-RA at an academic institution. We evaluated patients with nonmetastatic [ductal carcinoma in situ (DCIS), stage 1-3] breast cancer who received GLP1-RA (2005-2024). Linear regression models estimated associations between weight change and clinical factors. After excluding DCIS, propensity score matching (1:2) was used to match patients who received GLP1-RA with patients who did not, based on confounding covariates. Kaplan-Meier estimates and log-rank tests compared disease-free survival (DFS) and overall survival (OS) between GLP1-RA users versus nonusers in the subgroup with invasive disease. We identified 1,022 patients; 79% had type 2 diabetes mellitus. The median weight and body mass index at GLP1-RA initiation were 86.8 kg (47.2-175 kg) and 33.5 kg/m2 (18.9-61.8 kg/m2). In semaglutide or tirzepatide users (442, 43.2%), the median weight change at 3, 6, and 12 months after GLP1-RA initiation was -1.9% (-13.2% to 14.9%), -3.1% (-20.2% to 19%), and -2.6% (-27.8% to 11.5%), respectively. Endocrine therapy and metformin use were associated with weight gain and loss, respectively; invasive disease stage was linked to greater weight loss. GLP1-RA was not associated with DFS, but OS significantly differed between GLP1-RA users (n = 810) and nonusers (n = 1,620; hazard ratio, 0.37; 95% confidence interval, 0.27-0.53; P < 0.0001). In conclusion, in this real-world study in breast cancer survivors, GLP1-RA was associated with modest weight loss and improved all-cause survival. Clinical trials are warranted to study GLP1-RA in this population. SIGNIFICANCE: This is the largest study describing real-world patterns of GLP1 receptor agonists in breast cancer survivors. Clinical trials should evaluate these agents for weight management as an adjunct to lifestyle interventions and the potential role in cancer control in breast cancer survivors.