Key points:

• Diabetes increase mortality in people with cancer.
• Aging, sex, obesity, physical activity, diet, alcohol, and smoking are common risk factors for diabetes and cancer.
• Diabetic patients should have routine screening for cancer.

Both diabetes and cancer are prevalent diseases whose incidence are increasing and have a great impact on the health worldwide. Individuals with diabetes may have an increased risk of cancer. It has been observed that cancer and diabetes are diagnosed within the same individual more frequently than would be expected by chance. Studies suggest that diabetes may significantly increase mortality in people with cancer.

Evidence suggests that people with diabetes are at significantly higher risk for many forms of cancer. Diabetes, predominantly type 2 diabetes (non-insulin-dependent diabetes), has been associated to certain cancers, while prostate cancer occurs less often in men with diabetes. The risk for cancers of the liver, pancreas, and
endometrium are about two fold or higher and lesser for cancers of the colon and rectum, breast, and bladder in individuals with diabetes. Other cancers (e.g., lung) are not associated with an increased risk in individuals with diabetes.

About 80% of pancreatic cancer patients have glucose intolerance or frank diabetes. In patients with Type II diabetes, the pancreas is generally exposed to substantial hyperinsulinemia for years, suggesting that insulin may be involved in the association between long-standing diabetes and pancreatic cancer. Recently-developed glucose intolerance or diabetes may be a consequence of pancreatic cancer and that recent onset of glucose intolerance or diabetes may be an early sign of pancreatic cancer.

Type 2 diabetes and cancer share many common risk factors, but potential biologic links between the two diseases are not clear. Potential modifiable and non-modifiable risk factors common to both cancer and diabetes are shown in figure below. In addition, evidence suggests that some medications used to treat hyperglycemia are also associated with either increased or reduced risk of cancer.