MONDAY, June 26 (HealthDay News) -- Obese men with prostate cancer are less likely to benefit from radiation therapy than men who aren't overweight.

The finding may help doctors determine which patients -- particularly overweight ones -- need to have more aggressive treatment.

"Prostate cancer for most men is quiet. It's a cancer with a good outcome," said study lead author Sara Strom, associate professor of epidemiology at the University of Texas M.D. Anderson Cancer Center in Houston. "Basically, what you would like in prostate cancer is to identify men who have more chances of having a bad outcome, so you can do something different with them. Obesity is something to take into consideration," she said.

But another expert cautioned restraint when interpreting the findings, which appear in the Aug. 1 issue of the journal Cancer.

"Not many of the patients in the study were obese, so you can't make a very strong case for this paper, even though it's possible it's true," said Dr. Murugesan Manoharan, associate professor of urological oncology at the University of Miami Miller School of Medicine. "The study was also done in the past [1988-2001], and things have changed since them. We have newer radiation technologies," he noted.

Obesity is the root of many health evils, from diabetes to joint problems and, as is increasingly evident, even cancer.

Previous studies have shown that obese men with prostate cancer tend to have more aggressive disease and higher death rates. They are also more likely to have a malignancy that progresses after a prostatectomy, which is surgery to remove all or part of the prostate.

Researchers still didn't know how obesity might affect disease progression after radiation treatment. The new study sought to examine any relationship between obesity and progression of disease after external-beam radiotherapy. It is the first study of its kind.

Strom and her colleagues reviewed the medical records of 873 prostate cancer patients who had received external beam radiotherapy as the only treatment for their illness. Eighteen percent of the men in the group were mildly obese, and 5 percent were moderately to severely obese.

As the patient's body mass index (BMI, a ratio of weight to height) increased, the risk of disease progression following radiation therapy also increased. Moderately and severely obese men had a 99 percent greater risk of higher levels of prostate-specific antigen, a protein linked to the presence of prostate cancer. The obese men also had a 70 percent greater risk of tumor recurrence or metastasis.

"We found that after taking all the other important risk factors for a bad outcome into consideration, obesity is still associated with an increased risk not only of PSA going up but of having a cancer that returns and, in some cases, becomes metastatic," Strom said. "That's really the bad outcome," she added.

The study did not explore the reasons behind the findings, but Strom speculated that hormones, diet and genetic susceptibility may all play a role.

A second study in the same issue of the journal found that men with prostate cancer were driven more by emotion than any clear understanding of the clinical evidence when making their treatment decisions.

A study of 20 men with prostate cancer revealed a high level of fear and uncertainty, along with a desire to have rapid results and a tendency to shun second opinions. Men also displayed misconceptions about the effectiveness of different treatment options and tended to rely on anecdotal information about others' experiences with the disease.

Doctors need to take patients' fears and misconceptions into account when guiding treatment, the authors stated.

Manoharan agreed.

"Ideally, patients should make at least two visits, one for diagnosis and an overview of treatment," he said. "Then, bring them back after two weeks, after they have reviewed written information," he added.

And with prostate cancer, there is time for this luxury.

"Prostate cancer does not kill anybody so rapidly, so time is on the side of the patients," Manoharan said. "Patients should be given the important information that this cancer is not going to kill them immediately," he said.

More information

For more on prostate cancer, visit the National Cancer Institute.