Exocrine pancreatic cancer, cigarette smoking, and diabetes mellitus: A case-control study in Northern Italy

The role of cigarette smoking and diabetes mellitus as risk factors for exocrine pancreatic cancer ( PC) was investigated in a hospital based case-control study. Current smokers were at increased risk for PC (OR = 2.36, 95% CI 1.53 - 3.63): the magnitude of the risk was related to the lifetime amount of smoking (chi(trend)(2) = 17.00; P < 0.0001). Among former smokers, after 15 years from ceasing smoking, the risk for PC dropped to the level of a lifetime nonsmoker, whichever the lifetime smoking amount. Diabetes was associated with a 2.89-fold increased risk for PC (95% CI 1.71 - 4.86): the risk was 4.76 ( 95% CI 1.99 - 11.53) for diabetes diagnosed up to 2 years before the diagnosis of PC and dropped to 2.07 ( 95% CI 1.02 - 4.20) for diabetes diagnosed more than 5 years before PC. The risk for PC was estimated according to the treatment used to control diabetes: it was 6.49 (95% CI 2.28 - 18.48) for insulin treated diabetes and 2.12 ( 95% CI 1.16 - 3.87) for diabetes treated with oral hypoglycemic drugs. The risk of PC for diabetes treated for more than 5 years before the diagnosis of PC was 6.21 ( 95% CI 1.61 - 23.96) for patients treated with insulin and 1.21 ( 95% CI 0.50 - 2.92) for those treated with oral hypoglycemic drugs: the type of treatment needed to control the disease may discriminate between the diabetes that represents a consequence of cancer from the diabetes that could represent an etiological cofactor. More studies are needed to clarify whether long-lasting insulin-treated diabetes is an etiological co-factor in PC.