CANCER INCIDENCE IN A POPULATION-BASED COHORT OF PATIENTS HOSPITALIZED WITH DIABETES-MELLITUS IN DENMARK

Background: Diabetes has been associated with an increased risk of sev eral cancers, notably cancers of the pancreas, liver, endometrium, and kidney, Since most previous studies have involved a limited sample si ze or focused on specific cancer sites, we conducted a comprehensive a ssessment of the risk of cancer in a nationwide cohort of diabetics in Denmark, Methods: Discharge records of 109581 individuals hospitalize d with a diagnosis of diabetes from 1977 through 1989 were linked with national cancer registry records through 1993, Standardized incidence ratios (SIRs) were calculated for specific cancer sites, Results: The SIRs for primary liver cancer were 4.0 (95% confidence interval [CI] = 3.5-4.6) in males and 2.1 (95% CI = 1.6-2.7) in females, These SIRs remained elevated with increasing years of follow-up and after exclusi on of patients with reported risk factors (e.g., cirrhosis and hepatit is) or patients whose cancers were diagnosed at autopsy. Kidney cancer risk was also elevated, with SIRs of 1.4 (95% CI = 1.2-1.6) in males and 1.7 (95% CI = 1.4-1.9) in females, For both sexes combined, the SI R for pancreatic cancer was 2.1 (95% CI = 1.9-2.4), with a follow-up t ime of 1-4 years; this SIR declined to 1.3 (95% CI = 1.1-1.6) after 5- 9 years of follow-up, Excess risks were also observed for biliary trac t and endometrial cancers, The SIRs for kidney and endometrial cancers declined somewhat after exclusion of diabetics with reported obesity, Conclusions: Patients hospitalized with a diagnosis of diabetes appea r to be at higher risk of developing cancers of the liver, biliary tra ct, pancreas, endometrium, and kidney, The elevated risks of endometri al and kidney cancers, however, may be confounded by obesity.