Feb. 24, 2009 -- Millions of healthy men may benefit from talking to their doctors about taking the drug Proscar to prevent prostate cancer, according to new guidelines from the American Society of Clinical Oncology and the American Urological Association.
The recommendation is based on evidence gathered from 15 clinical trials, including the large Prostate Cancer Prevention Trial (PCPT) of over 18,000 men aged 55 and older. In that study, men who took a Proscar pill daily for one to seven years were about 25% less likely to develop prostate cancer than men who took a placebo.
Proscar is a type of drug known as a 5-alpha reductase inhibitor (5-ARI). These drugs lower the level of the hormone dihydrotestosterone, which can contribute to the growth of prostate cancer. Currently, 5-ARIs are used to treat certain noncancerous conditions, including male-pattern baldness and benign prostatic hyperplasia.
Another 5-ARI, called Avodart, is also being tested as a prostate cancer preventive. While the guidelines call for discussing the whole class of drugs with your doctor, only Proscar has been proven to reduce cancer risk to date, notes says Barnett S. Kramer, MD, MPH, associate director for disease prevention at the National Institutes of Health and co-chair of the guidelines panel.
The key recommendations in the guideline include:
- Men with a prostate-specific antigen (PSA) level of 3.0 or below who are screened regularly, or who plan to get yearly PSA tests and who show no symptoms, are encouraged to talk with their doctor about the risks and benefits of taking a 5-ARI to further prevent their likelihood of getting prostate cancer.
- Men who are already taking a 5-ARI for other conditions should talk to their doctor about continuing to use the drug for the prevention of prostate cancer.
"Since age is the key risk factor for prostate cancer, I'd suggest that all men aged 55 and older talk to their doctor about the risks and benefits," Kramer says.
The discussion is likely to be complicated. Among the factors to consider:
- When the findings from PCPT first came out, use of Proscar appeared to be associated with an increased risk of developing high-grade tumors, which are more likely to spread. A more thorough look at all the evidence now suggests "that the increase in high-grade cancers among men on Proscar was most likely an artifact," Kramer tells WebMD. Still, uncertainty exists.
- The therapy could prove costly and it is unclear whether insurance companies will pay. According to Kramer, "you would have to treat 71 healthy men for about seven years to prevent one case of prostate cancer."
- Prostate cancers are so slow-growing that many cancers prevented by the use of 5-ARIs may never cause harm in the first place.
- It is still not known whether taking a 5-ARI will reduce the risk of dying from prostate cancer or extend life expectancy.
- There are possible, though typically reversible, side effects associated with the use of 5-ARIs. They include an increased risk of erectile dysfunction and a decrease in libido and ejaculation volume.
- The use of 5-ARIs carries certain benefits, chiefly a decreased risk of lower urinary tract symptoms such as having trouble urinating.
Howard M. Sandler, MD, a prostate cancer specialist at Cedars-Sinai Medical Center in Los Angeles, says that he would consider taking a 5-ARI for prostate cancer prevention on a trial basis.
"If I tried it for a month or two and developed side effects, it would probably not be worth taking. But if I had no side effects, I probably would take it. It might help me sleep better at night," he tells WebMD.
The guidelines will be published in the March issue of the Journal of Clinical Oncology and the March issue of The Journal of Urology.