Obesity May Up Prostate Cancer Deaths

Obesity may more than double the odds of prostate cancer death among men newly diagnosed with the disease.

That news comes from researchers including Alan Kristal, DrPH, of Seattle's Fred Hutchinson Cancer Research Center and the University of Washington School of Public Health and Community Medicine.

"I was very surprised by the findings," Kristal says in a news release.

He notes that the risk was seen regardless of radical prostatectomy (surgery to remove the prostate), hormone therapy, low- or high-grade cancer, and prostate cancer spread.

If the finding is correct, it could be one more reason for men to reach and maintain a normal weight, but further study will be needed to prove that, Kristal says.

The study appears in the journal Cancer.

Prostate Cancer Study

The study included 752 men aged 40-64 and newly diagnosed with prostate cancer.

In interviews, the men provided their height and weight one year before their diagnosis.

Using those numbers, researchers calculated what the men's BMI (body mass index) had been one year before being diagnosed.

The researchers used BMI for the year before prostate cancer diagnosis in order to rule out any weight change from prostate cancer treatment.

Based on BMI, 17 percent of the men had been obese a year before being diagnosed with prostate cancer. Forty-nine percent had been overweight but not obese, and 34 percent had a normal BMI.

The men were followed for more than nine years, on average. During that time, 50 of them died of prostate cancer.

Obesity and Prostate Cancer

During the study, men who had been obese one year before prostate cancer diagnosis were 2.6 times more likely than men with a normal BMI to die of prostate cancer.

The results held when the researchers considered other risk factors, the prostate cancer's stage, and prostate cancer treatment.

Also, among men diagnosed with local or regional prostate cancer (cancer that hadn't spread far beyond the prostate), obesity in the year before diagnosis more than tripled the odds that the cancer would spread (metastasize)during the study.

Men who were overweight but not obese weren't more likely to die of prostate cancer or to have their prostate cancer spread than men with normal BMI.

Obesity a Risk Factor?

The study doesn't show how obesity might worsen prostate cancer prognosis.

Obesity may spur inflammation or hormonal changes that worsen prostate cancer outlook, the researchers suggest.

They note that neither prostate cancer death nor metastasis was very common in the study, which may have made it harder to detect subtle differences among the men.

In the late 1990s, other researchers found no link between obesity and prostate cancer death, metastasis, or recurrence. Kristal's team says that study included older patients than the ones they studied.

"It is possible that obesity is associated with poor prostate cancer
outcomes in younger men only, although a mechanism for such an effect is difficult to formulate," write Kristal and colleagues.

Next Steps

"I think this study represents the first good piece of evidence that
losing weight may in fact reduce the risk of dying of prostate cancer,"
Kristal says.

However, Kristal's team didn't test that theory, so further studies are
needed to find out if weight loss could cut prostate cancer death in obese
men.

"Although one would need a randomized clinical trial to definitively
determine whether weight loss could be an effective complementary treatment for obese men diagnosed with prostate cancer, these results offer yet another good reason for men to achieve and maintain a healthy weight," Kristal says.

By Miranda Hitti
Reviewed by Louise Chang
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