Drug cuts diabetics' pancreatic cancer risk: study

A diabetic patient injects himself with insulin at the J.W.C.H. safety-net clinic in the center of Skid Row in downtown Los Angeles July 30, 2007.

CHICAGO (Reuters) - Diabetics who took the drug metformin, which makes the body process insulin better, had a 62 percent lower risk of pancreatic cancer compared to those who had never received it, U.S. researchers said on Saturday.

But the risk of getting the cancer, one of the deadliest, was significantly higher among diabetics who took insulin or drugs that make the body produce more insulin, according to their study published in the journal Gastroenterology.

"We find that diabetics that had ever used metformin alone or in combination with other drugs had like a 60 percent reduced risk for pancreatic cancer, compared to diabetic patients who never used metformin," lead researcher Donghui Li from The University of Texas M.D. Anderson Cancer Center said.

Prior studies showed a lower cancer risk in diabetics who took metformin. The drug is used to treat type 2 diabetes, which is linked with poor diet and lack of exercise and accounts for about 90 percent of all worldwide cases.

"In addition, we see some increased risk of pancreatic cancer associated with the use of insulin and the use of insulin secretagogues." Those are drugs, such as sulfonylureas and glinides, which stimulate the pancreas to secrete more insulin or raise circulating levels of insulin.

Diabetics in the study who had taken insulin were nearly five times more likely to develop pancreatic cancer. And those who took insulin-stimulating drugs were 2.55 times more likely to develop pancreatic cancer.

Insulin is known to promote cell growth. "Insulin seems to have a growth promoting effect in cancer," Li said.

That interaction could help explain the findings of four recent studies published in the journal Diabetologia, which suggested the popular Sanofi-Aventis insulin drug Lantus might raise the risk of cancer.

The European Medicines Agency said last week flaws in the studies made the findings inconclusive, and Sanofi-Aventis said it would do further research in the area.

For her study, Li evaluated 1,800 people, including more than 900 who had pancreatic cancer and 350 with diabetes. The groups were matched by age, race and gender and completed detailed surveys of their health histories.

The study, however, was too small to find a benefit for people who had taken another popular type of insulin sensitizing drug in a class called thiazolidinediones, which include GlaxoSmithKline's rosiglitazone or Avandia and Takeda Pharmaceutical's pioglitazone or Actos.

Li said the study needs to be repeated in a bigger group of diabetics but added: "Our findings show metformin's potential as a chemopreventive agent."

There are dozens of diabetes drugs in different classes on the market. Metformin, available generically, is usually one of the first prescribed, with sulfonylureas such as glimepiride, sold by Sanofi-Aventis under the brand name Amaryl, added if patients cannot control blood sugar levels.

The American Diabetes Association already recommends metformin, which has been proven to lower the risk of heart disease.

(Editing by Maggie Fox and Paul Simao)