Good and Bad News About Diabetes and Cancer

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Two studies published in the past few weeks have examined ways in which diabetes, cancer, and their treatments affect one another. While one study found that having diabetes is associated with a worse cancer outcome, another found that a class of diabetes drugs may lower the risk of one of the most commonly diagnosed cancers.

A study published in the May 1 edition of the International Journal of Cancer revealed that people who have diabetes and are diagnosed with cancer tend to be treated less aggressively and have a worse prognosis than people without diabetes. The researchers examined the medical records of more than 58,000 people diagnosed with cancer between 1995 and 2002 and followed their outcomes through the end of 2004. They found that people with diabetes were more often diagnosed with more advanced tumors and tended to be treated with less chemotherapy and radiation than people who didn’t have diabetes. After adjusting for age, sex, stage of cancer, treatment methods, and cardiovascular disease (heart disease and stroke), the researchers found that people with diabetes and cancer had a higher rate of death than people with cancer but no diabetes.

Previous research has linked diabetes with a higher risk of developing certain cancers; in this study, the highest rates of diabetes were found in people with pancreatic cancer (19%) and uterine cancer (14%).

The researchers involved in this study said that their findings highlight how one chronic health condition and its treatment can influence the treatment and outcome of another chronic condition. They also emphasized the need for a multidisciplinary approach to treatment when a person has more than one chronic health condition.

Another study, published in the April 20 edition of the Journal of Clinical Oncology, showed that men with diabetes who took a Type 2 diabetes drug in the class known as thiazolidinediones had a lower risk of developing lung cancer than men with diabetes who didn’t take one of those drugs. The drugs rosiglitazone (brand name Avandia) and pioglitazone (Actos) are in the thiazolidinedione class. These drugs help people control their diabetes by making the body’s tissues more sensitive to insulin and causing the liver to release less glucose into the bloodstream.

The study looked at rates of lung, prostate, and colon cancer in more than 87,000 men with diabetes aged 40 and older whose medical records were in a Veterans Affairs database. After adjusting for other risk factors, the researchers found that men who were prescribed thiazolidinediones had a 33% lower risk of lung cancer. (Reductions in risk of colon and prostate cancer were not statistically significant.) The reduction in lung cancer risk was greater in African-American men than in white men.

The researchers warn that these findings are preliminary and that doctors should not prescribe these drugs for cancer prevention. Further studies are being designed to look more closely at this relationship.

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