Pancreatic cancer risk decreased by one anti-diabetic therapy, increased by others

The antidiabetic medication metformin is associated with a reduced risk of pancreatic cancer in diabetics, according to a new study in Gastroenterology, the official journal of the American Gastroenterological Association (AGA) Institute. However, other commonly used therapies, such as insulin or insulin secretagogues, may be associated with increased risk for the deadly disease.

"The current study demonstrated a robust protective effect of metformin against pancreatic cancer in diabetes. Our major observations were that diabetics who ever used metformin, especially those with greater than five years of use, had a reduced risk of pancreatic cancer compared to diabetics who had not taken these drugs," said Donghui Li, PhD, of The University of Texas M. D. Anderson Cancer Center and lead author of the study. "This adds evidence to previous study findings indicating that antidiabetic therapy can affect the development of cancer."

Study authors found that diabetics who took metformin had a 60 percent lower risk of pancreatic cancer, compared with those that had not taken metformin. This difference remained statistically significant when the analysis was restricted to patients with duration of diabetes greater than two years or those who never used insulin.

Other diabetes-associated factors, including history of smoking, overweight or obesity, and glycemic control, did not have a significant effect on the relationship between metformin use and pancreatic cancer risk. In contrast, diabetics who had taken insulin or insulin secretagogues had 4.99- and 2.52-fold increased risks for pancreatic cancer, respectively, compared with never-users.

This hospital-based, case-control study, conducted at M. D. Anderson from 2004 through 2008, involved 973 patients with pancreatic adenocarcinoma (including 259 diabetics) and 863 controls (including 109 diabetics). Pancreatic cancer risk was estimated using unconditional logistic regression analysis.

"Further study is needed in other study populations to confirm or refute a possible role of antidiabetic therapy in pancreatic cancer. Since pancreatic cancer is a rapidly fatal, but a relatively uncommon cancer, epidemiological research on this disease is challenging," Dr. Li added. "If the finding that metformin is protective against pancreatic cancer is confirmed, metformin may offer a tool for the primary prevention of pancreatic cancer among people with type II diabetes."

Pancreatic cancer is the fourth leading cause of death from cancer for both men and women in the U.S. The association of type II diabetes mellitus and pancreatic cancer is complex. On one hand, type II diabetes can occur as a consequence of pancreatic cancer. On the other hand, there is accumulating evidence to strongly support a significant role of type II diabetes in pancreatic carcinogenesis.

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