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

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.