Born to fight obesity, they could also become unexpected allies against cancer. At the ASCO 2026 conference, a series of studies showed that GLP-1 drugs are associated with fewer tumors and a lower risk of metastasis.
For years we have seen them as the drugs that have revolutionized the treatment of obesity. Today, however, semaglutide, tirzepatide, and the other GLP-1 receptor agonists are attracting attention for an entirely different reason. At the annual conference ofAmerican Society of Clinical Oncology (ASCO) 2026the most important global event dedicated to cancer, a series of studies has suggested that these medicines may not only promote weight loss, but also contribute to slow the progression of some tumors and perhaps to reduce its incidence.
The data that has caused the most discussion comes from ainternational analysis of over 12 thousand patients with tumors in the early or locally advanced stage. The researchers observed that patients treated with GLP-1 drugs after diagnosis had a significantly less likely to develop metastases compared to patients taking other antidiabetic drugs. The reduction in the risk of progression was particularly evident in lung, breast, colorectal and liver cancer. In some cases the probability of reaching stage IV has been reduced by between 31% and 50%.
This is not definitive proof. The authors themselves underline that the studies presented at ASCO are observational and do not demonstrate a direct cause-effect relationship. However, the growing number of concordant results is pushing the scientific community to look at GLP-1 with new eyes. According to several researchers, in fact, the benefits observed may not depend exclusively on weight loss, but also on direct biological effects on the mechanisms of inflammation, cellular metabolism and tumor growth.
The studies that sparked the debate
In the last two years, results have arrived that have attracted the attention of oncologists. One of the most cited works, published on JAMA Network Openanalyzed more than one million patients with type 2 diabetes, observing that users of GLP-1 receptor agonists had a lower risk of developing several obesity-related cancers than patients treated with insulin. In particular, the reduction appeared significant for colorectal, endometrial, ovarian and pancreatic cancers.
To strengthen the interest, a large study published in 2025 arrived JAMA Oncologywhich followed over 85,000 adults with overweight or obesity. Also in this case, an association emerged between the use of GLP-1s and a lower overall incidence of cancer. The most obvious benefits were endometrial cancer, ovarian cancer and meningioma. The authors, however, emphasized that these are observational data and do not demonstrate a cause-and-effect relationship. Meanwhile, a study published in 2026 on Annals of Oncology observed that nondiabetic obese patients treated with GLP-1 were 41% less likely to develop obesity-related cancers in the short term compared to controls. Even in this case the authors urge caution and ask for prospective trials to confirm the data.
Because they might work against some tumors
The most immediate explanation concerns weight loss. Losing weight reduces systemic inflammation, improves insulin sensitivity and lowers the levels of numerous growth factors involved in cell proliferation. In other words, by eliminating a part of the biological terrain favorable to the development of cancer, the oncological risk also decreases. But many researchers believe the phenomenon may be more complex. Some experimental studies suggest that GLP-1 receptors are also present in tissues other than the pancreas and can directly influence cellular processes related to inflammation, immunity and tumor growth. It is a field still in full evolutionbut sufficient to push several research groups to explore the possible role of GLP-1s as cancer prevention tools.
A particularly interesting element comes from comparison with bariatric surgery. In an Israeli study presented at the European Congress on Obesity, patients treated with GLP-1 agonists showed a reduction in the risk of obesity-related cancers comparable to that achieved with surgery, despite less weight loss. A result that fueled the hypothesis of biological effects independent of simple weight loss. Some recent analyzes are also suggesting possible benefits on breast cancer and colorectal cancer, two of the most common cancers in Western countries. However, these are preliminary results that require further confirmation.
The doubts of the experts and the questions still open
Despite the enthusiasm, the scientific community continues to maintain a cautious position. The reason is simple: almost all available evidence comes from observational studies. This means that scientists can identify statistical associations, but cannot prove that the drugs directly caused the reduction in cancer risk. There are also results that are not always in agreement. Some analyzes have reported a possible increased risk of kidney cancerwhile for other neoplasms, such as colorectal cancer, the conclusions remain the subject of discussion. The most recent reviews highlight that, overall, GLP-1s do not appear to increase the incidence of cancer and may even reduce it in some contexts, but the picture is still incomplete. Then there is a question of time. Cancer is a disease that often takes years, if not decades, to develop. GLP-1 drugs are relatively new and available observation periods may not yet be sufficient to grasp all the long-term effects. For this reason, numerous research groups are planning prospective studies and trials dedicated to oncological prevention. The conclusion, at least for now, is that i GLP-1 are not anticancer drugs and should not be prescribed with this objective. However, increasingly significant signs are emerging that suggest that their impact on health may go far beyond weight and blood sugar control. If the results are confirmed by future studies, the revolution begun against obesity could transform into something even more ambitious: a new strategy of cancer prevention. A perspective that until a few years ago would have seemed like science fiction and which today, however, is forcefully entering the international scientific debate.
