Obesity, Insulin Level Impact Prostate Cancer Survival

SUNDAY Oct. 5, 2008 -- Men who are overweight and who have high insulin levels when they are diagnosed with prostate cancer may be more likely to die from the disease, research shows.

This striking finding, published early online and expected to be in the November issue of The Lancet Oncology, is yet more reason to continue fighting the battle of the bulge, experts say.

"I don't want to be sensationalist, but obesity effects and the insulin effects are so big that I think if you had to choose between being thin and having a low insulin level or having access to the best chemotherapy, you would be more likely to survive without chemotherapy," said study senior author Dr. Michael Pollak, professor of oncology at McGill University in Montreal, Quebec, Canada.

"Tens of thousands of men are taking chemotherapy for prostate cancer -- as they should, because it is a good treatment. Doing so is actually helping," he said. "But potentially, dealing with insulin, obesity may one day be of more benefit."

The findings also have scientific import, giving researchers a clue that could lead to new prevention and treatment strategies.

Experts have long known that androgens, or male hormones, play a critical role in spurring prostate cancer.

In fact, these cancers are often treated with approaches that deprive the tumors of testosterone.

Smaller reports have suggested that obese patients with prostate cancer have a worse prognosis than patients of regular weight, though weight hasn't been related to actually developing a malignancy.

"We found in a large sample that obesity has a very important influence on prostate cancer outcome," Pollak said. "Then the question becomes, why would obesity make the outcome worse?"

Pollak and his colleagues looked at information on more than 2,500 men who had been followed for 24 years as part of the Physicians' Health Study. Information on body mass index (BMI) was available for all of these men, while information on C-peptide concentration (a marker of insulin levels in the blood) was available for 827 men.

Overweight men (those with a BMI of 25 to 29) had a 47 percent higher risk of dying from prostate cancer, while obese men (BMI of 30 or over) were more than two-and-a-half times more likely to die of the disease, compared with men of healthy weight (BMI under 25).

Men with the highest C-peptide concentrations also had more than double the risk of dying from their cancer compared with men with the lowest levels, the study found.

Finally, men who had a BMI of more than 25 and high C-peptide concentrations had quadruple the risk of dying from their cancer compared with men who had lower BMIs and lower C-peptide levels, the researchers reported.

"This suggests that there may be a whole new story to tell, whereby not just androgens have something to do with cancer behavior, but also insulin," Pollak said.

The insulin hormone may be latching onto insulin receptors located on prostate cancer cells, he speculated.

Some pharmaceutical companies are already testing drug candidates that target insulin signaling, Pollak added.

And the findings could have broader implications for other cancers, said study lead author Dr. Jing Ma, of Harvard University's Channing Laboratory.

"The simple things are still the important things. Don't drink, don't smoke, exercise, and eat well," said Dr. Ganesh Palapattu, assistant professor of urology, pathology and oncology at the University of Rochester School of Medicine. "This is yet another piece of evidence suggesting that obesity is not a good thing for many reasons."

"Obesity is the second leading cause of cancer death in this country next to tobacco," emphasized Dr. Jay Brooks, chief of hematology/oncology at Ochsner Health System in Baton Rouge, La. "Two years ago, I would never have told my patients that obesity is increasing their risk of death from cancer. Today, I do."

More information

There's more on prostate cancer at the U.S. National Cancer Institute.

Posted: October 2008


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