A new tool can help doctors estimate the risk of impotency for men deciding among various prostate cancer treatments, researchers said.
The tool, described September 20 in the Journal of the American Medical Association, provides formulas to help gauge those risks for three common treatments.
One expert called the findings a major step forward, but also warned patients and doctors not to use the results to choose between different types of treatment.
"It's really at this stage for the patient who has made up his mind that he's going to have surgery or radiation and then asks, 'What can I expect?'" said Dr Philipp Dahm, a urologist from the University of Florida in Gainesville who wasn't part of the study.
Erection problems after treatment
"This will give you a very good answer," he told Reuters Health.
In the new study, researchers used data from more than 1,000 men treated for prostate cancer at different hospitals across the country. All of the participants answered questions about their sex life before being treated with prostate surgery, external radiation, or brachytherapy.
More than a quarter of the men were impotent at baseline. Of those who weren't, 52% reported new erectile problems two years after their treatment.
In the surgery group, 60% of men who used to have a good sex life said they had become impotent. That figure was 42% among patients who received external radiation and 37% among those who had brachytherapy.
Obese men at higher risk
However, the chance of sexual problems varied greatly, depending on factors like age, race, weight, prior sexual function, blood levels of prostate specific antigen (PSA), hormone treatment and the specific kind of surgery.
For a normal-weight, 60-year-old African American with a good sex life, the chance that he would lose his ability to get an erection after brachytherapy was only 2%, for example.
An extremely obese 70-year-old white man getting the same therapy would have a 58% risk of becoming impotent.
"Sexual function is one of the things that are most commonly affected by prostate cancer treatment," said. Dr Martin G. Sanda, who heads the Prostate Centre at Beth Israel Deaconess Medical Centre in Boston and led the new study.
Formulas easily available
"Putting these formulas out there is really step one," he told Reuters Health. "Up to now there hasn't been something like this out there for side effects from prostate cancer treatment."
The next step is to make the formulas easily available, for instance as a web tool, and expand them to other side effects such as incontinence, Dr Sanda added.
He said the information necessary to calculate a man's risk isn't hard to get, and filling out the questionnaire would only take minutes.
His group also tested its predictions in a separate group of patients and found they held up well, although the individual risk estimates come with some uncertainty.
"In general for the surgical treatment the error bars might be a little broader, as much as 20% or 30%, than for some of the radiation groups," Dr Sanda said. "There is some variability, meaning there are some things that influence the outcome that may not be accounted for in the models."
In an editorial, Dr Michael J. Barry of Massachusetts General Hospital in Boston notes that the new formulas have some important limitations.
"First, this study is observational, and patients should use the findings cautiously to help choose among treatments," he writes.
Dr Dahm added that it is also important to look at other issues before choosing how to manage the disease, including cancer control and urinary problems.
"When patients make the decision they ideally should incorporate all these dimensions in their decision making," he said.
Nonetheless, he said he would use the new study when counselling patients.
"It provides the best available evidence out there," Dr Dahm concluded.
(Reuters Health, September 2011)