GLP-1 & Breast Cancer: Tracking Use & Outcomes

The burgeoning use of GLP-1 receptor agonists – initially hailed for diabetes and weight management – is now surfacing as a potentially significant factor in breast cancer care, according to research presented at the 2025 San Antonio Breast Cancer Symposium. This isn’t simply about helping patients lose weight before or during treatment; emerging data suggests a possible direct link between GLP-1 therapy and reduced tumor activity, a finding that could reshape supportive oncology strategies.

The Rising Tide of GLP-1s and the Oncology Connection

The rapid adoption of drugs like semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro) has been one of the most notable healthcare stories of the past two years. Initially focused on the type 2 diabetes epidemic, their dramatic efficacy in promoting weight loss quickly expanded their use – and demand – to include obesity management. Obesity is a well-established risk factor for numerous cancers, including breast cancer, both in terms of development and recurrence. This new research builds on preclinical work suggesting GLP-1 receptor agonists may have neuroprotective effects, and now extends that potential benefit to cancer outcomes.

The study, analyzing electronic health records from 2011-2025, reveals that 7.6% of breast cancer patients had documented GLP-1 use. Importantly, the data highlights *who* is accessing these medications. Patients with higher BMIs, non-Latinx Black individuals, those utilizing telemedicine, and residents of rural areas were more likely to be prescribed GLP-1s. Conversely, older patients, those with advanced-stage disease, patients with more aggressive tumor subtypes (HR-/HER2-), Latinx and Asian patients, individuals with limited English proficiency, and those receiving care at community centers faced barriers to access. These disparities are critical, as they suggest existing health inequities may be exacerbated by access to potentially beneficial therapies.

What Happens Next? The Path to Definitive Answers

The association between GLP-1 use and lower ctDNA positivity is the most compelling finding. ctDNA – fragments of tumor DNA circulating in the bloodstream – is a powerful biomarker for monitoring treatment response and detecting minimal residual disease. Lower positivity rates suggest GLP-1s might be impacting tumor burden or slowing cancer progression. However, correlation does not equal causation.

The immediate next step is rigorous clinical trials designed to specifically investigate the impact of GLP-1 receptor agonists on breast cancer outcomes. Researchers will need to control for confounding factors – such as lifestyle changes often associated with weight loss – and determine the optimal timing and duration of GLP-1 therapy in relation to cancer treatment. Expect to see trials evaluating GLP-1s as an adjunct to standard therapies (chemotherapy, radiation, endocrine therapy) and potentially even as a preventative measure in high-risk individuals. Furthermore, addressing the identified disparities in access will be paramount to ensure all patients can potentially benefit from these promising therapies. The conversation is shifting from weight loss as a secondary benefit to a potential direct anti-cancer mechanism, and the oncology community is poised to explore this avenue aggressively.

Reference

Ryals CA et al. Real-world glucagon-like peptide 1 use and association with clinical characteristics, social determinants, and circulating tumor DNA positivity in patients with breast cancer. Abstract PD8-07-02. SABCS 2025; 9-12 December.