New Test Predicts Risk for Impotence After Prostate Cancer Therapy
The strategy could someday be one more ingredient in the decision-making process for men faced with the choice of whether to undergo certain prostate cancer therapies or simply "wait and see" if the tumor becomes aggressive.
"With cancer in general the most important goal is to prolong life and ensure survival," explained study senior author Dr. Martin G. Sanda, director of the prostate center at Beth Israel Deaconess Medical Center in Boston, as well as an associate professor of urology at Harvard Medical School. "But with early-stage prostate cancer most men do survive." The question then shifts, he said, to doing a better job predicting the kind of side effects each individual is likely to suffer from treatment for the disease.
"So, what we've got here," said Sanda, "is a simple, quick, but valid questionnaire that can greatly facilitate treatment decisions by moving away from a one-size-fits-all approach."
Based on an assessment of pre-treatment sexual function, quality of life, and tell-tale clinical markers, the tool could offer much-needed clarity for newly diagnosed patients, experts say.
Sanda and his colleagues report their findings in the Sept. 21 issue of the Journal of the American Medical Association.
Diagnostic tests -- such as the prostate-specific antigen (PSA) blood test -- can suggest the presence of a prostate tumor. The trouble is, many of these tumors are so slow-growing as to pose little threat to a man's health. But since it's still difficult to identify aggressive tumors, the decision to undergo active treatment becomes a tough one.
Most treatments come with side effects, of course. For prostate cancer therapy that often includes erectile dysfunction (ED), incontinence, bowel dysfunction and other problems. In this study, the researchers focused on erectile dysfunction because among quality of life outcomes, loss of "sexual function in previously potent men" is the most common side effect, they noted, and is closely related to how men feel about the treatment outcome.
So, any test that might predict the likelihood of post-treatment ED in particular patients would be valuable. To help devise such a test, between 1995 and 2007 Sanda's team tried to see if they could accurately predict treatment-linked ED risk via pre-treatment questionnaires. They handed out the questionnaires to more than 1,200 newly diagnosed men.
The surveys noted patient age, prostate cancer severity, PSA levels, body mass index, race and ethnicity, current sexual function, and prior history of ED or ED treatment.
Ultimately, all the patients went on to undergo some form of therapy, and all were tracked for two years following treatment.
According to the researchers, a man's risk of erectile dysfunction varied depending on the type of treatment given. For example, for men with no ED issues before treatment, surgical removal of the prostate was associated with new-onset ED in about 60 percent of cases within 2 years of therapy. Just over 40 percent of men without prior ED experienced the problem following external radiation, the study found, and the figure dropped to below 40 percent for those who underwent brachytherapy [radioactive "seeds" embedded within the prostate].
A subsequent analysis of questionnaire responses revealed that certain patient characteristics, such as high PSA levels, were also associated with higher impotence risk.
Other key pre-treatment variables included age, race, BMI, and sexual history. These factors were then scored alongside some particulars of treatment itself (such as the use of nerve-sparing surgical approaches and/or hormone therapy-enhanced radiation).
The researchers say that the test was 77 to 90 percent accurate in predicting a man's risk for developing treatment-related ED, depending on the type of treatment received. It could also assess an individual's likelihood for developing ED along a continuum, ranging from as little as 10 percent risk up to a high of 70 percent.
"Basically, how patients are doing at baseline before treatment is the issue, in terms of ED risk," noted Sanda. "And this sort of one-page questionnaire can get at that in a clinical setting in less than five minutes, and [be] scored in a minute or two. So I would say that this is a move forward, a step in the right direction, with personalizing medicine."
Dr. Michael J. Barry is medical director at the John D. Stoeckle Center, part of Massachusetts General Hospital in Boston, and the author of an accompanying journal editorial. He said that the key issue here is "making sure that patients are fully informed of their health care choices".
"This is a great study, because it points towards a way to help people understand the trade-offs that are important when making decisions about their treatment," he said.
"Now this is only focusing on one, although common, piece of the equation," cautioned Barry, who is also president of the Boston-based Foundation for Informed Medical Decision-Making. "But, it can really help people weigh the potential benefits of reducing the risk of dying from prostate cancer versus the price they might have to pay. And that is what informed consent is all about."
There's more on prostate cancer treatment at the U.S. National Cancer Institute .
Posted: September 2011