Glucagon-like peptide 1 (GLP-1) receptor agonists—widely known for their role in managing type 2 diabetes and promoting weight loss—may offer benefits that extend into oncology. New data presented at the San Antonio Breast Cancer Symposium (SABCS) 2025 suggest that GLP-1 receptor agonists (GLP-1 RAs) are associated with improved outcomes in certain women with breast cancer, including enhanced overall survival and reduced treatment-related toxicities.

The findings come from a trio of large observational studies that collectively examined survival, disease characteristics, and chemotherapy tolerance among breast cancer patients receiving GLP-1 therapy.

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Growing Interest in Metabolic Drugs and Cancer Outcomes

Obesity, insulin resistance, and chronic inflammation are well-established risk factors for breast cancer development and progression, particularly in hormone receptor–positive disease. GLP-1 receptor agonists—such as semaglutide, liraglutide, and dulaglutide—improve glycemic control, promote weight loss, and exert anti-inflammatory effects, making them compelling candidates for investigation in cancer populations.

Until recently, however, clinical data linking GLP-1 therapy to breast cancer outcomes have been limited and inconclusive.

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Overview of the SABCS 2025 Studies

At SABCS 2025, investigators presented results from three independent large observational cohort studies, each examining different aspects of GLP-1 use in women with breast cancer.

Study 1: Overall Survival Benefit in DCIS and Early Breast Cancer

The first study evaluated women with ductal carcinoma in situ (DCIS) and early-stage invasive breast cancer who were prescribed GLP-1 receptor agonists for diabetes or obesity.

Key findings included:

• A statistically significant overall survival benefit among GLP-1 users compared with nonusers

• The survival advantage was most pronounced in patients with hormone receptor (HR)–positive, nonmetastatic disease

• Benefits appeared independent of traditional prognostic factors such as age and comorbidity burden

Investigators noted that these findings suggest GLP-1 use may influence disease biology or systemic health in ways that support improved long-term outcomes.

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Study 2: Survival Advantage in HR-Positive Nonmetastatic Breast Cancer

A second large cohort study focused specifically on women with HR-positive, nonmetastatic invasive breast cancer, the most common subtype of the disease.

Results showed:

• Improved overall survival among GLP-1 users

• A trend toward better disease-related outcomes in patients receiving endocrine therapy

• No evidence of increased recurrence risk associated with GLP-1 use

Researchers emphasized that the findings were particularly notable given the long natural history of HR-positive breast cancer, where modest improvements in survival can translate into meaningful clinical benefit.

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Study 3: Reduced Chemotherapy-Related Toxicities

The third study shifted focus from survival to treatment tolerability, examining patients undergoing chemotherapy for breast cancer.

Among patients receiving GLP-1 receptor agonists, investigators observed:

• Reduced rates of gastrointestinal toxicity

• Improved metabolic stability during chemotherapy

• Lower incidence of treatment interruptions and dose reductions

These improvements may reflect better glycemic control, weight management, and inflammatory modulation, all of which can affect chemotherapy tolerance.

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Potential Mechanisms Behind the Observed Benefits

Although causality cannot be established from observational data, several biological mechanisms may help explain the observed associations:

1. Improved Metabolic Health

GLP-1 RAs reduce insulin resistance and circulating insulin levels, which may limit tumor-promoting signaling pathways in hormone-sensitive breast cancers.

2. Anti-Inflammatory Effects

Chronic inflammation is linked to cancer progression and treatment toxicity. GLP-1 therapies have demonstrated anti-inflammatory properties that may mitigate these effects.

3. Weight and Adipose Tissue Modulation

Adipose tissue plays a key role in estrogen production after menopause. Weight loss associated with GLP-1 use may reduce estrogen-driven tumor growth in HR-positive disease.

4. Enhanced Treatment Tolerance

Improved metabolic control may allow patients to better tolerate systemic therapies, indirectly improving outcomes.

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Important Caveats and Limitations

Despite the encouraging findings, experts cautioned that these studies were observational, not randomized controlled trials. Potential confounders—such as healthcare access, socioeconomic status, and overall health behaviors—could influence outcomes.

In addition:

• GLP-1 use was not standardized across cohorts

• Duration and timing of therapy varied

• Long-term cancer-specific outcomes require further validation

As such, GLP-1 receptor agonists should not yet be considered cancer therapies, and their use should remain aligned with current indications for diabetes and obesity management.

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Clinical and Research Implications

The SABCS 2025 findings highlight the need for:

• Prospective clinical trials evaluating GLP-1 RAs in breast cancer populations

• Mechanistic studies exploring interactions between metabolic pathways and tumor biology

• Careful evaluation of safety and efficacy across breast cancer subtypes

If future trials confirm these benefits, GLP-1 receptor agonists could emerge as valuable adjuncts in the holistic management of breast cancer patients, particularly those with metabolic comorbidities.

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Conclusion

Once viewed primarily as weight loss and diabetes medications, GLP-1 receptor agonists are increasingly being recognized for their broader systemic effects. New data presented at SABCS 2025 suggest that these agents may improve survival and reduce treatment-related toxicities in certain women with breast cancer—especially those with hormone receptor–positive, nonmetastatic disease.

While further research is needed, the findings underscore the growing intersection between metabolic health and oncology and open new avenues for improving patient outcomes beyond traditional cancer therapies.