Weight-loss drugs such as semaglutide, part of a class of medications known as GLP-1 receptor agonists, are being studied to see whether they could also help prevent prostate cancer, according to Dr. Marcos Tobias Machado, a urologist and member of Brazil Health. He said recent studies have found some promising signals, but stressed that it is not yet known whether the drugs actually prevent the disease and they should not be used for that purpose.
Machado described the research as a new and promising line of investigation, not a proven treatment.
The link between obesity and prostate cancer
To understand where the theory comes from, Machado pointed to the relationship between excess weight and prostate cancer, which he said is more complex than simply saying obese men develop the disease more often. He noted that the evidence is more consistent for advanced and aggressive forms of the tumor.
The World Cancer Research Fund considers it probable that a greater amount of body fat increases the risk of advanced prostate cancer, Machado said.
He explained that researchers are studying several mechanisms behind this association. Obesity causes changes in insulin, metabolism, hormones and inflammatory processes in the body, creating an environment that can favor the development or progression of some tumors.
Because of this, properly treating obesity already brings important health benefits, Machado said. That raised a further question for researchers: could the medications used to treat obesity have an additional effect on cancer itself.
GLP-1 drugs draw attention from oncology
GLP-1 receptor agonists were originally developed to treat diabetes and later became important tools against obesity, Machado said.
He said researchers began observing possible associations between the drugs' use and the incidence of certain tumors. For prostate cancer, he pointed to two main hypotheses. The first is indirect: by promoting weight loss and improving metabolic changes linked to obesity, the drugs could alter factors related to cancer risk and progression.
Are the drugs linked to fewer cancer cases?
Machado said the results so far are provocative but not conclusive. A meta-analysis presented at the genitourinary cancers congress of the American Society of Clinical Oncology examined 56 randomized clinical trials involving more than 59,000 men.
According to the analysis, there were proportionally fewer prostate cancer diagnoses among men who received GLP-1 class drugs, 0.46 percent, compared with 0.55 percent in the comparison group.
However, Machado said the difference did not reach statistical significance, meaning the study could not demonstrate that the reduction was actually caused by the medications. He said a review published in 2026 reached a similar conclusion, with results trending toward a possible risk reduction but again without statistical proof.
At the same time, Machado said recent observational studies have found stronger associations, including a 2026 analysis that pointed to a lower incidence of prostate cancer among GLP-1 users in a population considered to be at higher risk. He said these studies are useful for generating hypotheses but cannot prove that the medication was responsible for any protective effect.
Not yet time to use the drugs for cancer prevention
Machado said this distinction is essential. There is currently no approved use of GLP-1 receptor agonists for preventing prostate cancer, and men should not start taking semaglutide or similar drugs believing it will protect them against the disease.
He noted that these medications have specific indications, contraindications and possible side effects, and must be prescribed according to each patient's individual clinical picture. They also do not replace established strategies for monitoring men's health and individually assessing prostate cancer risk.
Machado said what researchers are observing is something different and scientifically fascinating: medications created to control diabetes and later adopted for obesity treatment may have biological effects that are only beginning to be understood.
If future clinical trials show that GLP-1 receptor agonists do reduce prostate cancer risk, Machado said that would add a new dimension to drugs that have already transformed metabolic medicine.
For now, he said the most responsible answer remains the same: there is a signal, there is a hypothesis, and there is good reason to keep researching. But using weight-loss drugs to prevent prostate cancer, he said, is not yet a reality.
