JAMA Netw Open
GLP-1s tied to sharply better breast cancer outcomes
Clinical Takeaway: GLP-1 receptor agonists may offer protective benefit beyond weight and glycemic control in women with breast cancer and obesity or type 2 diabetes. Findings are observational, but support consideration of GLP-1 therapy when otherwise indicated.
Obesity and type 2 diabetes worsen breast cancer outcomes, raising the question of whether modern metabolic drugs can reduce that risk. Preclinical work has suggested GLP-1 receptor agonists may have anticancer effects, but their impact on real-world breast cancer survival had not been characterized.
The largest effects appeared in comparison to older treatments. Among women with breast cancer and obesity, GLP-1 users had a 65% lower ten-year risk of all-cause mortality and a 56% lower risk of recurrence compared with matched non-users. Ten-year survival was 96.0% with GLP-1 use versus 88.6% without. Among women with breast cancer and type 2 diabetes, GLP-1 users had a 91% lower risk of mortality and a 67% lower risk of recurrence compared with insulin or metformin users, with ten-year survival of 96.9% versus 76.4%.
To avoid overlap, the obesity cohort excluded patients with type 2 diabetes or an HbA1c above 6.5%, while the diabetes cohort included all eligible patients with type 2 diabetes regardless of BMI; women with both conditions appeared only in the diabetes analysis.
The picture shifts in relation to SGLT2 inhibitors, a modern antidiabetic class that also improves cardiometabolic outcomes. In unadjusted analyses, GLP-1 use was not associated with better survival or lower recurrence than SGLT2 inhibitors.
GLP-1s showed a modest advantage over SGLT2s in mortality (23% lower risk) and recurrence (16% lower risk), but the protective association for mortality did not persist in 12-month landmark analyses. The pattern suggests SGLT2 inhibitors may offer comparable benefit, and that part of the GLP-1 advantage seen against metformin and insulin may reflect differences between drug classes rather than a unique GLP-1 effect.
The analysis drew on electronic medical records covering 841,831 women diagnosed with stage I-III breast cancer between 2006 and 2023 across 68 health care organizations. Mean age was 69.
After 1:1 propensity score matching, three cohorts were compared: GLP-1 use versus non-use among patients with obesity (1,610 per arm), GLP-1 versus insulin or metformin among patients with diabetes (2,323 per arm), and GLP-1 versus SGLT2 inhibitors (4,052 per arm). GLP-1 exposure was defined as two or more prescriptions during the six months before or any time after diagnosis.
The findings add to a growing signal that GLP-1 receptor agonists may have effects relevant to cancer biology, but the comparison with SGLT2 inhibitors raises the possibility that broader metabolic improvement and not GLP-1 signaling specifically, drives much of the apparent benefit. Randomized trials in breast cancer survivors are needed to determine whether timing, duration, or drug class matters and to clarify how these agents interact with endocrine therapy.
"This study suggests that GLP-1 RAs may offer protective benefits beyond glycemic and weight control, potentially improving survival and recurrence risk in some female patients with breast cancer," the authors concluded.
Source: Tatum KL. JAMA Netw Open. 2026 May 11. Survival and Recurrence With GLP-1 Receptor Agonists in Breast Cancer