Obese men are less likely to benefit from radiation therapy for prostate cancer, a new study suggests.

Men who were considered moderately or severely obese had a 70 per cent greater risk of having a tumour recur or spread, despite radiation treatment, than non-obese patients.

Researchers tested for rising PSA levels to see if cancer was progressing.
(CBC)

Earlier results from the team at the University of Texas M. D. Anderson Cancer Center also found a history of weight gain or obesity around the time of diagnosis seemed to play a role in how aggressive the cancer became after surgery.

The study appears in the Aug. 1 issue of the journal Cancer.

Finding the same results from two groups of overweight patients taking different therapies points to how excess weight may influence tumour behaviour, said study author Sara Strom, a professor of epidemiology at the university.

A new study suggests being obese doesn't help certain prostate cancer patients.
(CBC)

"When patients and their physicians are uncertain about the need for further therapy, our research indicates that a man's weight should be factored into that decision," Strom said in a release.

The researchers looked back at the health records of 873 men whose prostate cancer was locally confined and who were treated with external beam radiotherapy between 1988 and 2001.

Only five per cent of the group were considered moderately to severely obese, which weakens the case for the link. The researchers defined obesity using the body mass index, a ratio of weight to height. 

The study's authors did not address why weight seems to play a role, though possibilities include hormones, diet and genetics.

Radiation technologies have improved since the study was done, and may be better able to target tumours surrounded by fat tissue, the study noted.

Emotion drives treatment decisions

A second study also appearing in the Aug. 1 issue of Cancer concluded men with prostate cancer tend to use emotion in making a treatment decision, rather than weighing clinical evidence.

Three factors entered into treatment decisions, Dr. Thomas Denberg of the University of Colorado at Denver found:

• Fear and uncertainty.
• Misconceptions about how well treatments work and their risks.
• Anecdotal information from other men's experiences with prostate cancer.

Although most of the 20 newly diagnosed patients knew prostate cancer grows slowly, such "abstract knowledge did little to dispel the vividly frightening, yet unlikely prospect of prostate cancer suddenly 'blossoming,'" the researchers wrote.