Authors:
Sapna Parmar, Sr. Clinical Pharmacist, OncoHealth
Richa Madurkar, Sr. Lead of Clinical Success and Strategy, Oncohealth
GLP-1 receptor agonists have transformed the treatment of type 2 diabetes and obesity. Now, researchers are exploring a new question: Could these medications also play a role in prevention of breast cancer or treatment?
Early findings have generated interest, with several studies reporting associations between GLP-1 use and breast cancer incidence, survival, or recurrence. But the evidence remains preliminary, and important questions about clinical benefit, patient selection, and cost are still unanswered.
For managed care leaders, this emerging research sits at the intersection of oncology outcomes, medication spending, and coverage policy. Understanding what the evidence shows, and where the gaps remain, will be essential as research evolves.
Why Are Researchers Looking at GLP-1s in Breast Cancer?
Cancer incidence continues to rise worldwide, with obesity and metabolic dysfunction emerging as key modifiable risk factors. Obesity increases the susceptibility to several different malignancies – among them breast, colorectal, esophageal, and endometrial cancers. In the United States (US), obesity is implicated in approximately 40% of all cancer diagnoses. Hyperglycemia is also a chronic risk factor for cancer development and progression through several mechanisms that create a pro-tumorigenic environment. In addition, obesity is associated with worse outcomes for several cancers, including breast cancer [1-2].
Glucagon-like peptide-1 receptor agonists (GLP-1s) are synthetic analogues of the GLP-1 hormone, which bind to the GLP-1 receptor and help regulate blood sugar levels and satiety signals. These agents have overwhelmingly altered the medical management of obesity and diabetes in the US and have emerged as medications of considerable interest in oncology. Initially approved for the management of diabetes in 2005, and to assist weight loss in 2014, the rise of these agents dramatically increased after 2020. As of December 2025, GLP-1s accounted for 7% of all prescriptions in the US [1-2].
An increasing number of patients with cancer are now prescribed GLP-1s at diagnosis or during treatment. GLP-1s are theorized to impact the risk of developing cancer and outcomes among those with cancer through four interrelated mechanisms: direct tumor cell effects, metabolic and hormonal modulation, immune enhancement, and anti-inflammatory action, but this has not been confirmed. To date, no randomized trial has been conducted to elucidate the role of GLP-1s in breast cancer prevention or outcomes [2].
Can GLP-1s Play a Role in Preventing Breast Cancer?
Several studies have examined the association between GLP-1 use and breast cancer incidence, with mixed findings and important limitations.
What the Studies Found:
A retrospective study of more than 100,000 patients
The most robust data come from a large retrospective cohort study of over 100,000 patients assessing the association between GLP-1 exposure and breast cancer risk in women aged 45-80 with a BMI ≥ 25 who underwent breast imaging [3]. GLP-1 exposure was associated with a lower incidence of breast cancer (odds ratio 0.649; 95% CI, 0.569-0.741). Of note, this study does not appear to account for known risk factors for breast cancer, such as BRCA1/2 mutation carriers, family history, or a personal history of atypical hyperplasia.
Recent findings presented at the 2026 ASCO Annual Meeting
Addressing the gap in the study described above, retrospective abstracts on the use of GLP-1s for primary prevention of breast cancer in high-risk, obese women were presented more recently at the 2026 ASCO Annual Meeting [4]. In one report, women aged 18-90 years with a BMI ≥ 30 who used GLP-1s were propensity-score matched to GLP-1 non-users. Breast cancer incidence was 2.95% in GLP-1 users versus 3.01% in non-users (3.27 vs 3.57 cases per 1,000 person-years.).
In a separate abstract [5], investigators retrospectively assessed the association between GLP-1 exposure and both breast cancer incidence and overall survival (OS) in women with elevated BMI and no history of diabetes. With a median follow-up of 36 months, GLP-1 users demonstrated a lower incidence of hormone receptor positive (HR+)/HER2 negative breast cancer relative to controls (absolute difference, −0.04%) and superior OS (HR 0.75; 95% CI, 0.65-0.86). Incidence did not differ significantly for HR+/HER2+, HR-/HER2+, or triple-negative breast cancer.
A nationwide study of approximately 900,000 adults
Finally, a nationwide cohort study published in July 2025 [9] evaluated the incidence of obesity-related cancer with GLP-1s compared to other glucose-lowering agents among approximately 900,000 overweight or obese adults with type 2 diabetes (T2D). GLP-1 users had a significantly lower risk of breast cancer (HR 0.84, 95% CI 0.78-0.91). Across all obesity-related cancers, incidence was lower with GLP-1 use compared to other glucose-lowering drugs (7.5 vs 8.1 per 1000 person-years).
The authors found the observed benefit in breast cancer diminished with decreasing weight.
What Does This Mean for Prevention?
In summary, several studies have sought to evaluate the potential effects of GLP-1s on reducing breast cancer incidence. However, varying patient populations and the retrospective nature of these studies limit the modest findings to hypothesis-generating only.
Prospective randomized trials in high-risk patients are needed to assess the role of GLP-1s and better define the populations most likely to benefit in terms of risk reduction and survival.
Could GLP-1s Play a Role in the Treatment of Breast Cancer?
Interest in GLP-1s extends beyond prevention to potential effects on outcomes among patients already diagnosed with breast cancer.
Standard treatments utilized for breast cancer such as cytotoxic chemotherapy, endocrine therapy, and treatment-induced menopause can further worsen weight gain, insulin resistance, and increase symptom burden, thereby potentially affecting treatment adherence. GLP-1s are theorized to potentially play a beneficial role by assisting weight loss, improving insulin sensitivity, and reducing systemic inflammation [1-2].
What the Studies Found:
Survival and recurrence outcomes
Tatum and colleagues conducted a retrospective cohort study [6] using TriNetX US Collaborative Network data to evaluate whether GLP-1 exposure is associated with improved survival and recurrence outcomes among women with stage I-III breast cancer and comorbid obesity or T2D. Three propensity score-matched cohorts were evaluated: patients with obesity (GLP-1 use vs non-use), patients with T2D (GLP-1s vs insulin or metformin), and patients with T2D (GLP-1s vs SGLT2 inhibitors). In patients with obesity, GLP-1 use was associated with substantially lower all-cause mortality (HR 0.35; 95% CI, 0.21-0.58) and improved recurrence-free survival (HR 0.44; 95% CI, 0.30-0.64) compared to non-use over 10 years. Among patients with T2D, GLP-1 use compared with insulin or metformin was associated with lower mortality and better recurrence-free survival. There was no significant difference when compared to SGLT2 inhibitors.
Findings from a large community oncology cohort
Abstract data presented at the 2026 ASCO Annual Meeting examined a large US community oncology cohort [7] and demonstrated that GLP-1 use was independently associated with improved OS after adjusting for age, BMI, stage, and cancer type (HR 0.58, 95% CI 0.40-0.84). The analysis encompassed breast, prostate, lung, hepatocellular, and kidney carcinomas, with the most common malignancies being breast (27%) and prostate (13%). Overall survival at 24 months was higher among GLP-1 users versus non-users for both breast and prostate cancers. GLP-1 use was most frequently observed among younger patients with obesity, and was commonly prescribed after cancer diagnosis, with semaglutide accounting for most prescriptions.
Cancer progression and tumor receptor expression
A second abstract presented at the 2026 ASCO Annual Meeting [8] reported a propensity-matched analysis in which GLP-1 therapy initiated after a diagnosis of stage I-III cancer was associated with significantly reduced progression to stage IV disease when compared to dipeptidyl peptidase IV (DPP-4) inhibitors in four of seven solid tumors: non-small cell lung, breast, colorectal, and hepatocellular carcinomas. Rates of adverse events were comparable between groups, and no meaningful safety signals emerged among GLP-1-exposed patients. In a parallel correlative analysis, elevated tumor GLP-1 receptor expression was independently associated with superior overall survival across all seven tumor types, with the strongest effect observed in breast cancer (HR 0.55, 95% CI 0.35–0.87).
Additional studies published in 2026
Finally, two additional studies published in 2026 have examined GLP-1s in patients with breast cancer. The first [10], a TriNetX analysis of postmenopausal women aged ≥ 50 years with obesity and stage 0-III disease, compared patients initiating a GLP-1 at least 6 months after diagnosis with those undergoing bariatric surgery in the same interval. Ten-year OS was similar (87% vs 83%), but GLP-1 users had a significantly lower mortality hazard (HR 0.57, 95% CI 0.45-0.73) and less locoregional recurrence (1.8% vs 4.7%); patients receiving both interventions fared best (OS 91% vs 80%; HR 0.44, 95% CI 0.29-0.67), which the authors interpreted as possible oncologic benefit beyond weight loss alone. The second [11], a single-institution propensity-matched 2-year landmark study from 2009-2025 of women with T2D and breast cancer found that post-diagnosis GLP-1 exposure was associated with lower overall mortality across 226 matched pairs (HR 0.51, 95% CI 0.28-0.93), including in those with stage I-III disease (HR 0.45, 95% CI 0.23-0.85).
What Are the Limitations?
These reports suggest that GLP-1s may be beneficial in breast cancer but again are limited by their retrospective nature. These studies evaluated GLP-1s in patients with FDA-approved indications for these agents (i.e. weight loss and T2D), therefore the potential benefit in the overall breast cancer population remains unknown. Lack of specific disease-related information – such as hormone-receptor status, stage or nodal status, surgical outcomes, and treatment – limit the ability to extrapolate the data into the clinical setting. Additionally, it is still unclear if these findings are due to weight loss alone or additional indirect mechanisms.
What Does All of This Mean for Managed Care?
GLP-1s have revolutionized the management of T2D and obesity. These benefits have led to increasing interest in their potential role in cancer treatment, specifically for patients with breast cancer. Obesity and metabolic dysfunction are known factors that promote the development, progression, and resistance to therapy in breast cancer, suggesting that drugs targeting these pathways may have anti-cancer effects. The evidence suggests that GLP-1s could become a novel class of agents linking metabolic health and breast cancer therapy.
For managed care leaders, several considerations stand out.
1. Clinical evidence must come first.
It is important to note that most of the current clinical data are retrospective and observational, subject to detection bias, prescription bias, and residual confounding. Well-designed, breast cancer-focused randomized controlled trials are needed to establish causality before these agents can be formally integrated into breast cancer prevention or treatment paradigms.
2. Cost-effectiveness will be critical
Cost-effective analyses are necessary to assess the economic viability of GLP-1s in breast cancer prevention and survivorship programs, given the high cost and disparities in access associated with these agents. In the US, annual spending on GLP-1s exceeded $71.7 billion in 2023. Widespread adoption without clear patient selection strategies could impose significant financial strain, highlighting the need for prospective randomized controlled trials to incorporate cost-effectiveness and equity analyses alongside clinical endpoints [12].
3. Coverage decisions should reflect the current evidence
As future trials continue to elucidate the underlying mechanisms and optimal positioning, GLP-1s have the potential to become an integral part of strategies bridging metabolic health and breast cancer treatment. Until more robust prospective data are available, no formal recommendations can be made to guide oncologists in clinical practice. Additionally, without an FDA approved indication or guideline support, health plans may not include coverage for GLP-1s as part of the cancer treatment paradigm. The use of GLP-1s in the oncology population outside of current FDA approved indications remains unestablished and warrants caution.
References:
[1] GLP-1 Receptor Agonists and Cancer—The Promise Is Real. Wender R. JAMA Network Open. 2026;9;(5):e2612143. doi:10.1001/jamanetworkopen.2026.12143.
[2] Metabolic Modulation in Cancer Care: The Potential Role of Glucagon-Like Peptide-1 Receptor Agonists. Temperley H, Kelly M. J Clin Oncol. 2026 Jun 29:JCO2600062. doi: 10.1200/JCO-26-00062.
[3] GLP-1 Agonists Are Associated With a Significant Reduction in Breast Cancer Incidence in Women. McDonald ES, et al. JCO Oncol Prac 2026 Jul;22(7): 1341-1348. doi: 10.1200/OP-26-00485. Epub 2026 Jun 2.
[4] GLP-1 receptor agonists for primary prevention of breast cancer in high-risk women: A real-world analysis of efficacy and safety. Gotera Nico-al. 2026 ASCO Annual Meeting Abstract. J Clin Oncol 44, 2026 (suppl 16; abstr 10520).
[5] GLP-1 therapy and hormone receptor–positive breast cancer risk and survival: A real-world analysis. Shah Z. 2026 ASCO Annual Meeting Abstract. J Clin Oncol 44, 2026 (suppl 16; abstr 10548).
[6] Survival and Recurrence With GLP-1 Receptor Agonists in Breast Cancer. Tatum KL, et al. Jama Network Open. 2026;9;(5):e2612133. doi:10.1001/jamanetworkopen.2026.12133.
[7] GLP-1 receptor agonist utilization and survival outcomes in a large US community oncology cohort. Sruti I. 2026 ASCO Annual Meeting Abstract. J Clin Oncol 44, 2026 (suppl 16; abstr 11017).
[8] Can GLP-1 receptor agonists mitigate cancer progression? A propensity-matched analysis across seven solid tumor types. Orland M. 2026 ASCO Annual Meeting Abstract. J Clin Oncol 44, 2026 (suppl 16; abstr 3143).
[9] Association between glucagon-like peptidase 1 receptor agonist and obesity-related cancer in overweight or obese patients with type 2 diabetes: a nationwide cohort study. Mao X, et al. J Natl Cancer Inst. 2025 Oct 1;117(10):2053-2061. doi: 10.1093/jnci/djaf163.
[10] GLP-1 Receptor Agonists vs Bariatric Surgery in Breast Cancer: A Comparative Study of Oncologic Outcomes. Den J, et al. Ann Surg 2026 Jun 16. doi: 10.1097/SLA.0000000000007121.
[11] GLP-1 receptor agonist use and overall survival among women with type 2 diabetes and breast cancer: a retrospective cohort study. Nelson RA, et al. Oncologist 2026 Jul 8;31(8):oyag268. doi: 10.1093/oncolo/oyag268.
[12] Spending on glucagon-like peptide-1 receptor agonists among US adults. Tsipas S, et al. Jama Network 2025. doi:10.1001/jamanetworkopen.2025.2964.