NEW YORK, Aug 21 (Reuters) Obese men have an increased risk of prostate cancer recurrence and death after they have completed radiation therapy, according to results of a study published in the medical journal BJU International.

Obesity is known to predict prostate cancer progression in men who undergo radical prostatectomy, or complete surgical removal of the prostate gland, Dr David Palma and colleagues from the British Columbia Cancer Agency, Vancouver, Canada, pointed out.

The researchers therefore examined whether obesity is associated with outcome for patients who undergo external beam radiation therapy for prostate cancer. Of 706 patients treated with radiation from 1994 through 2000, 195 were normal weight, 358 were overweight, and 153 were obese.

There were no significant differences among the three groups in Gleason score (aggressiveness of the tumor); prostate-specific antigen (PSA) score (a prostate tumor marker) before treatment began; or cancer stage (how far the cancer has spread).

Blood levels of the male hormone testosterone were lower in obese men than in overweight and normal-weight men.

There were a total of 292 treatment failures detected by laboratory tests. The average times to relapse for normal-weight, overweight, and obese men were 93 months, 88 months, and 84 months, respectively.

The average times to prostate cancer death were 11.1 years for normal and overweight men, and 10.6 years for obese men, a statistically significant difference. The results of further analysis revealed a trend toward decreased overall survival by weight group.

''A number of explanations have been postulated to account for more aggressive prostate cancer in obese men,'' Palma and colleagues note. ''Possible mechanisms include dietary factors, and alterations in hormonal levels, such as estrogens, androgens, leptin, and IGF-1, although definitive mechanisms have not been elucidated.'' REUTERS SV BST0828