Diabetes and the risk of pancreatic cancer

Diabetes occurs more frequently in patients with pancreatic cancer than in the general population, and it has repeatedly been claimed that it is a risk factor for this tumor. However in most of the studies on this subject the duration of diabetes before the diagnosis of pancreatic cancer was not ascertained. In an attempt to clarify the cause of the association between these two pathologic conditions and to determine whether diabetes is a risk factor for pancreatic cancer we recently studied this association in a large number of patients with pancreatic cancer.

A total of 720 patients with newly diagnosed pancreatic cancer (415 men and 305 women; mean age 62.6 years, range 22 to 79 years) and 720 controls matched for sex, age, social class, and geographic region, 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.

One hundred sixty-four patients with pancreatic cancer (22.8%) and 60 controls (8.3%) had diabetes. In the majority of the patients with pancreatic cancer (56.1%), diabetes was diagnosed either concomitantly with the cancer (in 40.2%), or within two years before the diagnosis of cancer (in 15.9%). The association between the two conditions was significant (odds ratio, 3.04; 95% 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% 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.

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.