Diabetes and the risk of pancreatic cancer

Background. Diabetes and pancreatic cancer are known to be associated, but the cause of the association and whether diabetes is a risk factor for pancreatic cancer remain controversial. Methods. A total of 720 patients with pancreatic cancer and 720 control patients from 14 Italian centers were enrolled in the study. All subjects were interviewed personally and in detail about their clinical history. The diagnosis of diabetes was based on criteria recommended by the American Diabetes Association. Results. One hundred sixty- four patients with pancreatic cancer (22.8 percent) and 60 controls (8.3 percent) had diabetes. In the majority of the patients with pancreatic cancer (56.1 percent), diabetes was diagnosed either concomitantly with the cancer (in 40.2 percent), or within two years before the diagnosis of cancer (in 15.9 percent). The association between the two conditions was significant (odds ratio, 3.04; 95 percent confidence interval, 2.21 to 4.17). However, when only patients with diabetes of three or more years' duration were considered, the association was no longer significant (odds ratio, 1.43; 95 percent confidence interval, 0.98 to 2.07). All the patients with pancreatic cancer whose diabetes had been diagnosed before the cancer had non-insulin- dependent diabetes; all but one of the control patients with diabetes had the non-insulin-dependent form of the disease. Conclusions. Diabetes in patients with pancreatic cancer is frequently of recent onset and is presumably caused by the tumor. Diabetes is not a risk factor for pancreatic cancer.