18-Year Study Finds Drug Cut Prostate Cancer Risk
Follow-up focused on finasteride, the active ingredient in Proscar and hair-loss drug Propecia
"It shows that the higher proportion of high-grade disease doesn't really matter, because it doesn't affect the risk of death," said Dr. Otis Brawley, chief medical officer for the American Cancer Society.
Brawley said the increased diagnosis of high-grade prostate cancer likely occurs due to finasteride's effectiveness in shrinking enlarged prostates.
"You take Proscar for six months to a year and it halves the size of your prostate, but the cancer inside your prostate does not shrink," Brawley said. "If I'm performing a biopsy on a smaller prostate, I'm more likely to hit that cancer than if I am sticking into a larger prostate. This drug wasn't causing more prostate cancer. It's causing more prostate cancer to be diagnosed."
Since finasteride does not affect survival rates, its true value may lie in reducing the diagnosis of minor prostate cancers that should not be treated, Thompson and Brawley said.
Prostate cancer is the most commonly detected form of cancer in men, found in one in six men during their lifetimes, Thompson said. Prostate cancer kills only 3 percent to 5 percent of men, however.
Most men "will get away with it, dying of causes other than prostate cancer," Thompson said.
Because of this, prostate cancer has become an overtreated disease, with men suffering side effects such as impotence and incontinence because they received treatment for a cancer that wasn't likely to lead to their deaths, Brawley said.
"It does not affect a man's risk of death at all to take finasteride, but if he takes finasteride it will lower his risk of being diagnosed with prostate cancer," Brawley said. "Half to 60 percent of men who were diagnosed with localized prostate cancer, if it was never diagnosed, it would never have bothered them in their lifetimes. We cure some people who never need to be cured."