Cancer risk in patients with type 2 diabetes mellitus and their relatives

Epidemiological studies indicate that risks of certain cancers are increased in individuals hospitalized for type 2 diabetes mellitus (T2DM), which may not be representative of the entire population of T2DM patients as most of them are treated in primary health cares. To examine the subsequent cancer risk in individuals with T2DM from hospitals and primary health cares, and in their siblings and spouses, standardized incidence ratios (SIRs) were used to assess systematically risks of 35 cancer sites/types in individuals with T2DM using a nationwide Swedish database covering the period 1964 through 2010. Increased SIRs were recorded for 24 cancer sites/types in individuals with T2DM. The highest SIRs were for pancreatic cancer and liver cancer (2.98 and 2.43, respectively). A decreased SIR was noted for prostate cancer. Five cancers showed increased SIRs during the whole follow-up period: colon, liver, pancreatic, endometrial and kidney cancers. T2DM patients in inpatient, outpatient and primary health care showed similar risk patterns. The overall SIRs for cancer in the siblings and spouses of individuals with T2DM were 0.97 and 1.01, respectively. The insulin users showed an overall increased risk of cancer. This study showed increased risks of 24 cancers in individuals with T2DM, but not in their siblings or spouses, suggesting that the profound metabolic disturbances of the underlying disease may explain the observed increases. Further studies examining the endogenous and exogenous factors underlying these associations are needed. What's new? Environmental and genetic factors could be at work in predisposing patients with type 2 diabetes mellitus (T2DM) to malignant disease, but the degree to which either set of factors raises cancer risk in T2DM is unclear. In this study, cancer risk among T2DM patients and their siblings and spouses was assessed using data from health registries in Sweden. Members of the T2DM cohort had an overall increase in risk for 24 different cancers. Similar increases were not detected among relatives, indicating that shared environmental and genetic factors may have limited influence on cancer risk in T2DM.