By Michael Kahn

LONDON, Aug 16 (Reuters) - Women who had gestational diabetes when pregnant may be at greater risk of developing pancreatic cancer, according to U.S. and Israeli researchers who said the study was the first to link the two diseases.

Previous studies have shown that people with type-2 diabetes faced increased risk of pancreatic cancer, but the new results show a connection to the less common form of diabetes caused by the release of certain hormones and weight gain during pregnancy, researchers said.

Pancreatic cancer is particularly lethal because it is often diagnosed late in its development and only about five percent of people with the disease survive for five years. More than around 200,000 new cases are diagnosed worldwide each year.

Mary Perrin, a researcher at New York University's School of Medicine, said the findings need to be confirmed in further studies, but are important because gestational diabetes appears to be increasing as obesity rates rise.

"What makes this study important is -- other than a potential to develop type-2 diabetes -- not much is known about gestational diabetes, which may be an earlier marker of risk of other health outcomes like pancreatic cancer," Perrin, who led the study, said in a telephone interview.

Diabetes has become more common in the United States and elsewhere in recent decades thanks in part to growing rates of obesity. An estimated 20.8 million Americans have diabetes, mostly type-2.

Some studies have shown diabetes can be an early symptom of pancreatic cancer. It is caused when the body fails to properly use and sometimes produce insulin, made in the pancreas.

In the study in BMC Medicine on Thursday, the researchers traced health records of nearly 40,000 women who gave birth between 1964 and 1976 in Jerusalem as part of a study.

Because the records are so detailed in Israel, researchers were able to track the women to find out how many developed pancreatic cancer later in life.

The study found that of 410 women diagnosed with gestational diabetes in one or more pregnancy, five got pancreatic cancer.

The findings represent a statistically significant level of risk and merit further study of links between the two diseases, said Perrin. She added that the absolute risk was very low.

"It really would need to be confirmed in other studies but it shouldn't alarm anyone who has had gestational diabetes that they are destined to get pancreatic cancer," she said.

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