Weight-loss drugs linked with lower risk of obesity-related cancers

Blockbuster weight loss and diabetes drugs may lower patients' risk of developing some common types of cancer that are closely linked to obesity, new evidence suggests.

Patients with Type 2 diabetes who were prescribed drugs known as glucagon-like peptide-1, or GLP-1, developed fewer obesity-related cancers than patients who were treated with insulin, according to a study published Friday in JAMA Network Open. But the newer drugs didn't perform better than metformin, an older diabetes drug with known cancer risk reduction properties.

The group of drugs the study looked at includes Novo Nordisk A/S's Ozempic, a diabetes treatment. Since the study concluded, two drugs that work in similar ways were approved for weight loss, Novo's Wegovy and Eli Lilly & Co.'s Zepbound.

The study is based on electronic health records for more than 1.6 million patients with Type 2 diabetes for 15 years ending in November 2018. Since that was less than a year after Ozempic was introduced in the US, most of the GLP-1 patients in the study would have been taking first-generation medicines, such as Novo's Victoza, said Lindsey Wang, a rising second-year student in the BS-MD program at Case Western Reserve University, who did the data analysis.

Still, the study is the latest evidence to suggest that widely popular diabetes and weight-loss shots may have a role in cancer prevention. Additional studies, including ones that assign people randomly to take GLP-1 drugs or other treatments, will be needed to establish whether the drugs can truly prevent certain types of cancer.

"Obesity is the tobacco of our age when it comes to cancer risk," said Arif Kamal, chief patient officer of the American Cancer Society. Kamal said the early evidence on GLP-1s is "compelling."

The drugs have been used for almost two decades, but the newer, more powerful versions have caused the market to balloon. With millions of people now taking them, scientists are beginning to discover new potential uses "- and some surprising side effects. The drugs have set off a gold rush for Big Pharma, with analysts at Goldman Sachs estimating the market for obesity alone could reach $130 billion by the end of the decade.

Cancer links

Excess body fat is known to increase the risk of developing 13 specific types of cancer making up 40% of all cancer diagnoses in the US, according to the Centers for Disease Control and Prevention.

In the JAMA study, patients who were prescribed GLP-1s were almost 50% less likely to develop colon cancer than patients who were treated with insulin alone. GLP-1s were also associated with a lower risk of developing other tumors of the digestive system, including esophageal cancer, gallbladder cancer and pancreatic cancer.

"This is very significant because usually when you get these cancers, you have a poor prognosis," said Wang. She conducted the research under the guidance of Case Western Professor Nathan Berger, who died last month at the age of 83.

In one finding that Wang said surprised researchers, the drugs did not appear to reduce risk of post-menopausal breast cancer. There was also no impact on thyroid cancer. Patients who took GLP-1s were more likely to develop kidney cancer than those who took metformin.

However, trying to track associations like these via electronic health records is "very problematic," said Anne McTiernan, a professor of epidemiology at the Fred Hutch Cancer Center, who wasn't on the research team and reviewed the study results.

"Electronic health records do not accurately portray other health conditions beyond the condition for which billing is done," she said in an e-mail, noting that the dataset in the study didn't accurately portray use of alcohol and also may have underreported the number of overweight patients in the study who had a family history of colon polyps.

And US drug labels for both Ozempic and Wegovy carry a warning about thyroid tumors in rodents, saying it's unknown whether the drugs cause the tumors in humans.

The European Medicines Agency studied the issue last year after independent research pointed to the potential of an increased risk of thyroid cancers when people with Type 2 diabetes use the medicines, but found no evidence to support a causal association. Other studies have reached similar conclusions.