By Leslie Wade
CNN Medical Producer
Type 2 diabetes may increase the risk of developing cancer, according to a joint statement released by the American Diabetes Association and the American Cancer Society.
"The evidence is very strong, about a twofold higher risk of cancer among those with diabetes: liver cancer, pancreatic cancer and endometrial cancer. And to a lesser extent, diabetes looks to be a risk factor for colorectal cancer, breast cancer and bladder cancer," says Susan Gapstur, vice president of the Epidemiology Research Program at the American Cancer Society.
Some connections between the diseases are easier to decipher than others, researchers say. They looked at shared risk factors, biologic links, and the effects of drug treatment.
Both diseases are more common in those who are older, obese, physically inactive and have poor diets. These shared risk factors offer some explanation. Complex biology offers more clues.
"Some of the factors that may contribute to a cell becoming a cancer might include high insulin and glucose levels that result from diabetes," Gapstur explains. That's to say, spikes in insulin and blood sugar levels at different times throughout the course of the disease. Hormone-like substances from fat are also suspected of playing a role in promoting cancer.
Scientists are also looking at the possible link between diabetes treatment and cancer, though the evidence is mixed. Some studies suggest that metformin, a common type 2 diabetes drug, actually lowers the risk of cancer. Other research seems to indicate that insulin treatment may increase the risk. Experts encourage patients to talk to their doctor if at very high risk for cancer, before making any changes in treatment.
So what can diabetics do to reduce their chances of developing cancer? "First and foremost, prevention is key," explains Gapstur. She stresses the urgency of adapting healthy lifestyle habits such as maintaining a healthy weight, eating a balanced diet, and getting plenty of exercise. And have a conversation with your doctor about cancer screenings because catching early signs of cancer may make all of the difference.