Efficacy of GLP-1 Receptor Agonists in Breast Cancer Populations

Recently published data in the journal ONCOLOGY focused on GLP-1 receptor agonist use for patients with breast cancer. Investigators aimed to study weight change among this population to determine if there was a benefit to its use.

Sherry Shen, MD, assistant attending physician at Memorial Sloan Kettering Cancer Center, and the lead author on the study, spoke to CancerNetwork® about the results from the trial and how she is using that data to propel her research forward. The retrospective cohort study showed a mean weight loss of 5% at 12 months with no clinicopathologic variables significantly associated with the weight loss.

To read more about GLP-1s and their use in cancer care, visit: cancernetwork.com/view/obesity-and-cancer-risk-the-evolving-role-of-glp-1s-in-oncology

Transcript:

Our main question was, following a breast cancer diagnosis, [are] our patients who take GLP-1s able to lose weight? I will caveat this entire conversation by saying that this was a small study. Ours was among the first, maybe the first study, that was published on GLP-1s in breast cancer, but it was a very small cohort that came out of Memorial Sloan Kettering. We have to take some of the findings with a grain of salt, but we looked at 75 patients—all stages of breast cancer—who were taking GLP-1s. Most of them, about 80%, were taking the GLP-1 for a diabetes indication, not for a weight management indication. These drugs became approved for weight management only as recently as 2021, so they haven’t been on the market for obesity and for weight [loss] for very long. About 80% of the patients were taking it for diabetes reasons, and among the total cohort, that average weight loss at 1 year was 5%.

Now, if we think about this in the context of the GLP-1 phase 3 trials for weight management purposes, those range from weight loss of approximately 8% at 1 year all the way up to almost 20% with tirzepatide, which is also known as Mounjaro or Zepbound. That’s one of the more recently FDA-approved GLP-1s for weight management indications. Eight [percent] to 20% is what we’re seeing in [patients without cancer], and in our breast cancer population, we saw a more modest 5%. Again, [it was] mostly for a diabetes indication, which is dosed slightly differently. Most of our patients were on endocrine therapy or [had] hormone receptor–positive breast cancer.

One of the real takeaways here is that it’s possible that patients with breast cancer, especially those who are taking active anti-cancer treatments, may have a harder time losing weight, even with GLP-1s. On the other hand, 5% is a meaningful amount of weight loss. I just mentioned a post-diagnosis weight gain of over 10% is associated with worse outcomes, so if that 5% weight loss can be combined with additional lifestyle factors, that gets towards attenuating that weight gain that patients may see and can be meaningful in terms of patients’ quality of life, how they tolerate their endocrine therapies, how they feel, and their body image. This can be a meaningful option for patients, but of course, many more studies are needed and have come out since we published ours.

Reference

Shen S, Liu B, Fanti C, et al. GLP-1 receptor agonist use and weight change in patients with breast cancer. Oncology (Williston Park). 2025;null(7):294-296. doi:10.46883/2025.25921046