Obesity's effect on survival after prostate cancer Tx is minimal

Obesity does not appear to independently predict long-term prostate cancer survival after primary treatment of the disease, according to two new studies.

Researchers from the Mayo Clinic tapped their institution's database of nearly 15,000 men who have undergone radical prostatectomy in the PSA era. After identifying 5,314 men with documented height and weight data, and who underwent radical prostatectomy between 1990 and 1999, the researchers divided the subjects into three cohorts, according to National Cancer Institute-designated groupings of obesity.

With increasing body mass index, there was a progressively greater risk of high-grade (Gleason score of 7 or greater) cancer: 30.6% in those with a body mass index of 25 or less; 32% in those with a BMI of 25 to 29; and 40.3% in those with a BMI of 30 or higher, according to study author Michael L. Blute, MD, Mayo Clinic College of Medicine, Rochester, MN.

With a median 10.1-year follow up, BMI did not appear to have an impact in multivariate regression analyses on cancer-specific survival.

In a second study of nearly 6,500 men treated for localized prostate cancer, researchers found that being obese did not significantly impact the need for secondary treatment, nor did it result in decreased overall or disease-specific survival.

Lead author Phillip L. Ross, MD, of the University of California, San Francisco, and colleagues looked at a large database of men with prostate cancer from 31 sites around the country and identified 6,416 men with clinically localized prostate cancer treated between 1995 and 2005.

The researchers categorized patients into four weight groups: normal (less than 25 kg/m²), overweight (25 to 29.9 kg/m²), obese (30 to 34.9 kg/m²), and very obese (35 kg/m² or more). Following the subjects for a median 36.1 months, the researchers reported that the presence and type of secondary treatment was not associated with BMI.

Dr. Ross said that while this study suggests no association between BMI and prostate cancer outcomes, additional studies are needed to get to the bottom of this controversial issue.