Cancer is a general term that can be applied to more than 200 diseases. Characterized by abnormal cell division, cancer typically invades and destroys healthy tissues in the body.  According to authorities such as the American Medical Association, the American Cancer Society and the National Institutes of Health’s National Cancer Institute, individuals with diabetes and prediabetes are at increased risk for developing and dying from certain types of cancer.

Research has most strongly linked diabetes to:

• Colorectal cancer
• Pancreatic cancer
• Endometrial cancer
• Liver cancer

Some research also associates diabetes with greater risk of esophageal cancer, cervical cancer, oral cancer, stomach cancer and other tumors.

The relationship between diabetes and cancer remains unclear. Experts have postulated that obesity, a hallmark of type 2 diabetes, predisposes many diabetic patients to various cancers. Some researchers suggest that factors such as obesity, diet and use of alcohol explain higher diabetic rates of cancer. Other research indicates that insulin resistance (a condition in which the body produces insulin but is unable to use the hormone properly) and hyperinsulinemia (elevated levels of insulin in the blood) promote the growth of cancer cells.

However, obesity, insulin resistance and hyperinsulinemia are traits of type 2 diabetes, not type 1 diabetes, which has also been linked to increased risk of some cancers. For example, a 10-year study of births in Sweden, a nation with one of the highest rates of type 1 diabetes, found that children of women with type 1 diabetes had more than double the risk of childhood cancer.

Researchers are still trying to explain the connection. Some experts believe that certain hormonal changes associated with diabetes may boost the risk of tumors. For instance, scientists found in 2006 that a molecule called p110 alpha, a common pathway for cancer, also helps control insulin and other hormones involved in diabetes.

Another diabetic risk factor for cancer: immunosuppressive drugs, which patients take after an islet cell transplant, pancreas transplant or kidney transplant.

Even in the majority of cancers not caused by diabetes, having diabetes can complicate recovery. Corticosteroids, some chemotherapy drugs and radiation can cause hyperglycemia. Patients may need fast-acting insulin added to their insulin regimen. Even nondiabetic cancer patients may need to begin treatment with insulin and in some cases are at risk of secondary diabetes. Hormone therapy for prostate cancer (hormonal medication or surgical removal of the testicles) has also been linked to risk of developing secondary diabetes.

Diabetes treatments may one day be used to fight cancer. For example, scientists are exploring whether thiazolidinediones, a class of antidiabetic agents, have a role in treating malignant and benign tumors.

Cancer studies may also lead to treatments for diabetes. For instance, cancer researchers found that a gene mutation involved in an endocrine tumor condition called multiple endocrine neoplasia may lead to a way to grow pancreatic islet cells. And some immunosuppressives used to treat lymphoma are being studied as a possible treatment for type 1 diabetes.