Diabetes, chronic kidney disease and cancer risk.

The possible association between diabetes and cancer was first launched in 1932, when cancers in the intestine, uterus and pancreas were reported to occur more frequently among patients with diabetes [1]. However, it took some 70 years before the scientific community once more focused on this association. Several observational studies published over the last 10–15 years show unequivocally that there is an association between certain forms of cancer and type 2 diabetes. Figure 1 shows the relative risk for patients with type 2 diabetes to develop cancers by organ of origin. The relative risk appears to be highest for liver, pancreas and endometrial cancers [2–4]. There is also a 20–50% increase in incidence of breast, colon, kidney and bladder cancers [5–8], whereas cancer of the prostate actually appears to occur at a lower rate in these patients, although the outcomes of prostate cancer may be worse once established [9]. Indeed, it is a general finding that once the cancer has been diagnosed, the chance of dying from the cancer is higher in patients with diabetes than in patients without diabetes [10]. A difficulty in inferring a cause and effect relationship between type 2 diabetes and cancer is that both conditions are more prevalent with age and also with obesity. Obesity itself increases the risk of certain cancer forms, e.g. endometrial cancer, breast cancer, kidney cancer, colorectal cancer and pancreas cancer [11], and obesity itself also increases the risk of dying from the cancer disease [12]. It has therefore been postulated that the mechanism for cancer related to type 2 diabetes at least in part is a consequence of metabolic dysfunctional changes associated with obesity, insulin resistance, hyperinsulinaemia and also hyperglycaemia. The cancer rate is increased also in type 1 diabetes, but the cancer forms differ from type 2 diabetes in that the stomach, the cervix and the endometrium are the predominant sites in this condition [13].