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Diabetes drug metformin may help fight lung cancer
Last reviewed: 03.07.2025
Metformin, already the drug of choice for millions of people with type 2 diabetes, may also fight lung cancer in these patients, according to a new study.
Metformin appears to help boost the effects of immunotherapy drugs used to treat lung tumors, according to a team led by Dr. Sai Yendamuri, chief of thoracic surgery at Roswell Park Comprehensive Cancer Center in Buffalo, N.Y.
However, there was one important nuance to this discovery.
"Our studies show that the anticancer effect of metformin is only active in the context of obesity," Yendamuri said in a Roswell news release. "We observed longer recurrence-free survival in overweight patients who took metformin and underwent surgery."
The study was published in the Journal of the National Cancer Institute.
Lung cancer remains the leading cause of cancer deaths in the United States. Nearly 235,000 new cases are diagnosed each year, and more than 125,000 people die from lung cancer, according to the American Cancer Society.
According to the researchers, it has previously been suggested that metformin may have anti-cancer properties, although clinical trials have failed to confirm this.
Yendamuri speculated that this may be because the effect was only seen among obese patients.
He designed a new study to test this hypothesis. It included 511 patients with lung cancer and a BMI of 25 or higher (above the threshold for overweight/obesity) and 232 patients with a BMI below 25, which is not considered overweight.
All patients had non-small cell lung cancer (NSCLC), the most common form of the disease, and all had undergone surgery to remove the tumor.
The second group included 284 overweight patients and 184 normal-weight patients who received an immunotherapy known as a checkpoint inhibitor.
"Our studies show that the anti-cancer effect of metformin is only active in the context of obesity," Yendamuri reiterated. "We observed longer recurrence-free survival in overweight patients who took metformin and underwent surgery."
How does metformin work against cancer? Studies in mice suggest that the drug appears to reduce the damage that obesity does to the human immune system.
This could make immune-targeted cancer drugs more effective, but only in obese people.
"By drawing attention to the potential of metformin-containing regimens to improve clinical outcomes in patients with obesity, we hope to inspire further research," said study co-author Joseph Barbee.
"We believe our findings provide a rationale for testing drug combinations that may have the potential to prevent or more effectively treat lung cancer in this growing group of patients," said Barbie, an associate professor of oncology in the division of immunology at Roswell Park.
Barbie and Yendamuri are planning a clinical trial to test metformin's potential to prevent lung cancer in overweight or obese people who are at high risk of the disease.
"Metformin has been around for 30 years, it has a long safety record — and it's one of the most widely available and inexpensive drugs of any kind," Yendamuri said. "If we can repurpose it to fight cancer, that would be incredibly exciting."