Obesity tied to higher pancreatic cancer risk

NEW YORK (Reuters Health) - New research suggests that obesity may raise older adults' risk of developing pancreatic cancer, one of the deadliest forms of the disease.

The study, by researchers at the U.S. National Cancer Institute, found that men and women who were severely obese were 45 percent more likely than normal-weight adults to develop pancreatic cancer over five years.

Abdominal obesity, in particular, was linked to a higher risk of the disease among women, the researchers report in the American Journal of Epidemiology.

Pancreatic cancer is difficult to catch early, and 95 percent of patients die within five years of being diagnosed. Because of this dismal prognosis, researchers consider it particularly important to pinpoint the modifiable risk factors for the disease.

Smoking is one such risk factor. Some studies have also implicated obesity and physical inactivity in contributing to pancreatic cancer, possibly because of their association with type 2 diabetes.

In type 2 diabetes, the body loses its sensitivity to the blood sugar-regulating hormone insulin, which is produced by the pancreas; this leads to persistently high levels of insulin in the body. Insulin has growth-promoting effects, and it's thought that too much of the hormone may encourage pancreatic tumor cells to grow and spread.

In the current study, the relationship between obesity and pancreatic cancer weakened somewhat when the researchers factored in diabetes.

This suggests that diabetes is one reason obesity is linked to pancreatic cancer, according to the researchers, led by Dr. Rachael Stolzenberg-Solomon.

"Our results, as well as those of others, may have important implications for cancer prevention particularly related to the avoidance of obesity," the researchers write.

The findings are based on data collected from more than 300,000 U.S. adults who were cancer-free and between the ages of 50 and 71 at the outset. Over roughly five years, 654 developed pancreatic cancer.

In general, the risk of the cancer climbed in tandem with body mass index, a measure of weight in relation to height. Severely obese study participants were at greatest risk. Among women, the odds of developing pancreatic cancer also increased along with waist size.

There was no relationship, however, between the disease and physical activity levels. Going into the study, the researchers note, they had hypothesized that regular exercise would lower the risk of pancreatic cancer -- given that it helps manage weight and type 2 diabetes.

It's possible, they write, that the study did not precisely measure people's activity levels, and more research is needed to see whether or not exercise helps reduce pancreatic risk.

SOURCE: American Journal of Epidemiology, March 1, 2008.