Finasteride revisited: Does it lower prostate cancer risk?[SIZE=-1]An article in the New York Times last summer asked whether the drug finasteride (Proscar, and also generic) could help prevent prostate cancer for older men. There's been some controversy about finasteride, which is normally used to treat an enlarged prostate, but some of the experts quoted gave a clear message. "There is a tremendous public health benefit for the use of this agent,? said Dr. Howard Parnes, chief of the prostate cancer group at the National Cancer Institute.
So, should older men take finasteride to lower their risk of prostate cancer? In their guidelines on the topic, the American Society of Clinical Oncology and the American Urological Association hedge their bets. They say that healthy men with normal blood work, who are also having regular screening for prostate cancer, "may benefit from a discussion of both the benefits [of finasteride...] and the potential risks."
Why no firm recommendation one way or the other? Well, screening for prostate cancer is slightly controversial in the first place. A blood PSA test PSA test can pick up early signs of a tumor, but many prostate cancers grow so slowly that they never get big enough to cause problems. Therefore, having surgery after a positive blood test that leads to a diagnosis will put you at risk of various side effects, including incontinence and erection problems, to get rid of a cancer that might not have hurt you in the first place.
Another cause of uncertainty is the variety of ways the research on finasteride has been interpreted. One large study clearly found that men taking finasteride were less likely to get prostate cancer. In fact, the results were so clear that the trial was stopped early. About 18 in 100 men taking finasteride got prostate cancer, compared with 24 in 100 men who didn't.
Unfortunately, the men who did get prostate cancer while taking finasteride seemed to have worse tumors. About 6.4 in 100 men from the finasteride group got a more aggressive form of prostate cancer, compared with 5.1 in 100 men who took a placebo.
What was going on? Could finasteride be giving people the worst possible deal: preventing minor, harmless cases of prostate cancer, but actually causing the more aggressive kind?
When researchers examined the data again, they hit on another theory. Maybe finasteride didn't cause aggressive tumors; maybe it just made them easier to find. Finasteride shrinks the prostate gland, and searching in a smaller space means you're more likely to find what you're looking for. Imagine the guys from CSI searching around a dark area with flash lights. It's easier to find something on a bathroom floor than on a football field. Finasteride might have just been making biopsy results more sensitive.
Another effect of finasteride is to reduce levels of PSA in your blood. Higher PSA levels are the warning sign that prostate screening tests look out for. So, a drug that lowers your PSA might cut the chance of being offered a biopsy to look for cancer cells, and make it less likely that you'll be diagnosed in the early stages.
Where does all this leave us? The June 2008 edition of The Medical Letter (subscription required) breaks it down. One possibility is that finasteride prevents prostate cancer. The other is that it stops you being diagnosed in the early stages (remember that earlier diagnosis might be better if you want to have treatment). Finasteride might cause more aggressive tumors, or just make them easier to detect. The article concludes: "Until more evidence becomes available, the conservative course would be not to take it."
There are also side effects of finasteride to bear in mind. About 67 in 100 men who take it get erection problems, compared with 62 in 100 men taking a placebo. And 65 in 100 have a lower sex drive, compared with 60 in 100 men taking a placebo. There's also the financial cost of treatment, and the fact that insurers might not cover it.
Even after having gone through the evidence to write this blog, I don't have a clear picture of whether finasteride is beneficial or not. I can't help but think of an article I read this week by a British doctor, saying that too many healthy, older people are turned into patients by doctors too keen to prescribe preventative treatments with very minor benefits.
What you need to know. One interpretation of the research on finasteride is that it cuts the risk of prostate cancer. However, the experts don't agree. Get your doctor to explain the potential risks and benefits before you decide anything.
?Philip Wilson, patient editor, BMJ Group
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Read more on the risk factors and tests for prostate cancer, and find out what treatments work for an enlarged prostate (subscribers only).
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