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Baldness drug may reduce prostate cancer risk

But it could trigger more aggressive form in other cases

(CNN) --A study released Tuesday indicates that a drug used to treat male pattern baldness reduces the odds of getting prostate cancer by about 25 percent.

But there's some bad news: The same study seems to show that if a man taking finasteride does get the disease, the drug appears to increase his chance of getting a more aggressive form.

"Finasteride is the first drug found to reduce the risk of prostate cancer," said Dr. Ian Thompson of the University of Texas Health Science Center at San Antonio, the study's lead author. "The drug worked for men at low risk for prostate cancer, as well as those at high risk."

The National Cancer Institute estimates that if 1,000 63-year-old men are tracked, after seven years, 60 of them would develop prostate cancer, with 18 of those men suffering with high-grade tumors, which spread quickly.

If the same men took finasteride for seven years, only 45 would get the cancer, but 22 would have the more aggressive tumors.

A low-dose version of finasteride used to treat hair loss is marketed under the trade name Propecia, while under the name Proscar it's sold as a treatment for enlarged prostates.

In the study, which was funded by the National Cancer Institute and published in the online version of the New England Journal of Medicine, researchers at 221 sites nationwide followed nearly 19,000 men older than 55 for seven years.

About half of them were assigned at random to take either finasteride, a drug that lowers male hormone levels, or a placebo.

By the end of the trial, those taking the drug reduced their risk of prostate cancer by nearly 25 percent over those on placebos.

Mortality in both groups was the same: Five in each group died of prostate cancer.

Promoter of mean types of cancer?

But researchers were not convinced that men should take the drug to prevent the disease, which, after skin cancer, is the most common form of cancer among men. While the men who took finasteride were diagnosed with fewer cases of the disease, they had more high-grade prostate cancers, which typically are more aggressive than other forms.

In all, 6.4 percent of the men on finasteride had high-grade tumors, versus 5.1 percent of men on placebos.

The reason for that disparity was not clear. Thompson said finasteride may result in the development of more aggressive tumors either by preventing only low-grade tumors or by making the prostate gland more favorable to aggressive tumors.

Dr. John Wasson, director of the Center for Aging at Dartmouth Medical School in Hanover, New Hampshire, and who served on the study's safety monitoring committee, said the tumor findings raised a number of questions: "What really is finasteride doing here? Is it a promoter of mean types of cancer, or a suppresser of meaningless types?"

The study was stopped a year earlier than planned because it was determined that the extra time was unlikely to yield new information. In addition, Wasson cited concerns over the apparent increased risk of more aggressive tumors.

Though the study is a major step forward, men should carefully weigh their options before opting to take the drug as a preventive measure, Dr. Harmon J. Eyre, chief medical officer of the American Cancer Society, said in a statement.

"There are still some important unanswered questions, especially regarding side effects, whether it can benefit men at increased risk, especially African Americans, who are twice as likely as white men to die of prostate cancer, and the mechanism by which men taking the drug develop higher grade tumors."

Other side effects

Despite the concerns, Dr. Nabil Khawand, a physician at Washington Hospital Center, said he would leave the decision to his patients. "I will tell him the result of the study and I will give him the option, whether he wants to be on it or he doesn't want to be on it."

Apparent side effects went beyond tumor aggressiveness. Men taking finasteride were more likely than men on placebo to experience sexual side effects such as impotence.

But men taking the placebos were more likely to be diagnosed with enlarged prostate and urinary problems.

This year, prostate cancer is expected to be diagnosed in more than 200,000 men and kill about 29,000 in the United States. It is typically a slow-growing cancer and most of the men who are diagnosed with it go on to die of something unrelated, even if they undergo no treatment for it.

For young men using the drug to promote hair growth, "I certainly wouldn't want to be taking a drug that potentially promotes cancer of the mean types," Dartmouth's Wasson said. "First, do no harm, that's the bottom line with any drug or treatment ... if you're a young guy, you should really be concerned about finasteride."

He predicted the study results would lead the Food and Drug Administration to take a fresh look at the safety data on the drug, which is made by Merck and requires a prescription. No one from the agency was immediately available to comment, and a call to the drug maker was not immediately returned.

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