GLP-1s Show Promise in Breast Cancer: Survival, Toxicity Data Emerge

Emerging research continues to reveal potential benefits beyond metabolic health for GLP-1 receptor agonists, now suggesting a possible role in improving outcomes for individuals with breast cancer. Several studies presented at the San Antonio Breast Cancer Symposium indicate these medications may extend survival, reduce recurrence risk, and mitigate chemotherapy-related toxicity across various disease subtypes, though investigators emphasize the necessitate for prospective validation.

Early Signals of Benefit

GLP-1 receptor agonists, initially approved for type 2 diabetes in 2005 and subsequently for obesity in 2014, have garnered attention for their potential anti-cancer effects. These medications work by reducing glucose levels, decreasing inflammation, and improving insulin resistance – all factors implicated in cancer development and progression. Prior research has linked GLP-1s to a reduced risk of obesity-related cancers and even suggested superiority to aspirin for colorectal cancer prevention. Recent data similarly points to benefits in hematologic malignancies, showing reduced mortality and slower disease progression.

At the San Antonio Breast Cancer Symposium, at least eight posters explored the efficacy and safety of GLP-1s in breast cancer patients. Three specifically examined the impact on recurrence risk and overall survival. A study by Ali Younas Khan and colleagues at West Virginia University, utilizing data from the TriNetX global health research network, found a 64% lower risk of invasive or metastatic breast cancer and a 63% reduction in risk of death among patients receiving hormonal therapy for ductal carcinoma in situ who were also using GLP-1 receptor agonists.

Another study, led by Fayaz Khan at Roswell Park Comprehensive Cancer Center, focused on patients with ER-positive metastatic breast cancer. Results showed significantly improved two-year overall survival and a reduced risk of hospitalization for those using GLP-1s. Importantly, GLP-1 users also experienced lower rates of anemia, thrombocytopenia, and severe sepsis.

Colton Frisco Jones, MD, and colleagues at The University of Texas San Antonio analyzed data from over 17,500 patients with obesity and breast cancer. Their findings, presented at the symposium, revealed a 46% reduction in all-cause mortality among GLP-1 users, a benefit consistent across various subgroups defined by age, BMI, diabetes status, and endocrine therapy type.

Understanding the Mechanisms and Potential Concerns

Whereas these retrospective studies are promising, Jasmine Singh Sukumar, MD, assistant professor at The University of Texas MD Anderson Cancer Center, cautions that the results require prospective validation. The precise mechanisms underlying these benefits remain unclear. Sukumar notes that the observed improvements could stem from a direct anti-tumor effect or from the broader metabolic health benefits conferred by GLP-1s. Preclinical data are emerging that support both possibilities.

Although, researchers also acknowledge potential drawbacks. One concern is the possibility that GLP-1s may exacerbate side effects associated with endocrine therapy. A study by Jones and colleagues found higher rates of endocrine therapy side effects, including joint pain, depression, and osteoporosis, among GLP-1 users. This finding is consistent with the known effects of GLP-1s on the hypothalamus-pituitary-thyroid axis and weight reduction. Another area of concern is equitable access to these medications, as highlighted by Cleo A. Ryals, PhD, of Flatiron Health, who found disparities in GLP-1 use based on race, ethnicity, age, and socioeconomic factors.

Chemotherapy-Related Toxicity Mitigation

Beyond hormonal therapies, research suggests GLP-1s may also reduce chemotherapy-related toxicity. Elvis Obomanu, MBBS, LMCC, and colleagues at Jefferson Einstein Philadelphia Hospital analyzed data from over 11,000 patients receiving chemotherapy for breast cancer. Their findings showed significantly lower rates of various cardiovascular, gastrointestinal, hematologic, and systemic toxicities among GLP-1 users, including mucositis, neutropenia, and sepsis. Here’s particularly noteworthy, as chemotherapy-induced side effects often lead to treatment disruption or discontinuation.

The Equity Question and Future Directions

Despite the promising signals, access to GLP-1s remains uneven. Ryals’ research, using data from Flatiron’s research database, revealed that GLP-1 use was lower among older patients, those with advanced disease, Asian and Latino individuals, and those treated in community practices. These disparities underscore the need for strategies to ensure equitable access to these potentially beneficial medications.

Joanne Mortimer, MD, FACP, FASCO, of City of Hope, emphasizes the importance of well-designed prospective controlled trials to confirm these findings. While the retrospective data are encouraging, the potential for bias and confounding factors necessitates rigorous investigation. Future trials should incorporate lifestyle interventions, including diet and exercise, to maximize the benefits of GLP-1s.

The evolving understanding of GLP-1s in oncology represents a significant area of research. As more data emerge, these medications may become an increasingly important component of comprehensive breast cancer care. However, careful consideration of both the potential benefits and risks, as well as equitable access, will be crucial to optimizing outcomes for all patients.

For more information:

Colton Jones, MD, can be reached at [email protected]

Joanne Mortimer, MD, FACP, FASCO, can be reached at [email protected].

Elvis Obomanu, MBBS, LMCC, can be reached at [email protected].

Jasmine Singh Sukumar, MD, can be reached at [email protected].