A man’s weight may affect his prostate cancer prognosis and raise the risk of the disease progressing, according a new study.

Researchers found men who were obese at the time their prostate cancer was diagnosed as well as those who gained weight quickly before their diagnosis were more likely to have an aggressive form of the disease. These men were more likely to have prostate cancer that progressed after surgical treatment.

Although previous studies have suggested a link between obesity and the risk of developing prostate cancer, researchers say this is the first study to show a relationship between a man’s weight at different ages and the risk of prostate cancer progression after diagnosis and surgical treatment.

Researchers say if further studies confirm these results, doctors should consider a man’s weight and his history of weight gain when designing a prostate cancer treatment plan, such as incorporating diet and exercise strategies to reduce the risk of prostate cancer progression.

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Obesity Tied to Prostate Cancer Progression

In the study, published inClinical Cancer Research, researchers followed 526 men with prostate cancer who were treated with surgery (prostatectomy). The study lasted about 4.5 years.

Researchers checked whether the men had rising prostate-specific antigen (PSA) levels following their initial prostate cancer treatment, which the researchers call biochemical failure.

"After surgery, a patient's PSA should go back to being undetectable, but if it begins to rise, that is an indicator of progression," researcher Sara Strom, PhD, associate professor at the University of Texas M.D. Anderson Cancer Center, says in a news release.

"Thirty percent of men who have biochemical failure will develop a life-threatening cancer metastasis, and so PSA is the only marker we have as yet to predict whose cancer will spread."

Overall, 18 percent of the men experienced biochemical failure, and the results showed that the men’s weight was associated with the risk of prostate cancer progression in at least three ways:

—Men who were obese at the time of prostate cancer diagnosis were more likely to experience rising PSA levels than those who were not obese. Obesity is defined as having a body mass index (BMI, a measure of weight in relationship to height) of 30 or more.

—Men who were obese at age 40 had a greater rate of biochemical failure.

—Men who gained weight at the greatest rate between age 25 and the time of their prostate cancer diagnosis experienced disease progression significantly sooner (after an average of 1.5 years) compared with those who gained weight more slowly during adulthood (an average of 3 years).

"These findings support the view that the development of aggressive forms of prostate cancer may be influenced by environmental effects that occur early in life," says Strom.

Researchers say it’s unclear exactly how obesity contributes to prostate cancer risk but possible explanations include hormonal changes, poor diet, and low physical activity.

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By Jennifer Warner, reviewed by Brunilda Nazario, MD

SOURCES: Strom, S. Clinical Cancer Research, Oct. 1, 2005; vol 11: pp 6889-6894. News release, University of Texas M.D. Anderson Cancer Center.