Help or harm for prostate cancer?
Mary Duenwald
Thursday, June 26, 2003

NEW YORK A drug that doctors had hoped might prevent prostate cancer has been found to be both more effective and potentially more dangerous than expected.

After giving a daily dose of the drug, finasteride, sold by Merck under the brand name Proscar, to more than 4,300 healthy older men for seven years, researchers found that the men's chances of getting prostate cancer were 25 percent lower than for those of a like-size group of men who took placebos, according to a report released online by The New England Journal of Medicine.

But 280 of the men who took finasteride, or 6.4 percent, ended up with especially aggressive cases of prostate cancer, compared with 237 in the placebo group, or 5.1 percent. Whether or not a man should take finasteride to prevent prostate cancer is "an individual decision for a man and his physician," said Charles Coltman Jr., chairman of the Southwest Oncology Group in San Antonio, Texas, and a leader of the study.

Men who stand a particularly high risk of developing prostate cancer - black-Americans and men with close relatives who have had the disease - might consider taking the drug as a preventive measure, Coltman said. In the study, the drug proved to be as protective for high-risk men as it was for others.

But Peter Scardino, head of urology at Memorial Sloan-Kettering Cancer Center, in New York City, who wrote an editorial about the study for the journal, said most men should not take finasteride, because the possibility of developing a more aggressive form of cancer appeared to be too great. "The 25 percent reduction in cancers is quite impressive, and I think this study opened an enormous area of research," Scardino said. "But when doctors look at this carefully, I don't think they're going to prescribe Proscar to people to prevent prostate cancer."

Coltman said the National Cancer Institute ended the 10-year study 15 months early, not because it concluded that finasteride was dangerous but because the results had already conclusively demonstrated the drug's mixed effects. "More information wouldn't have changed the outcome," he said.

The men who took finasteride experienced a greater number of sexual problems, including reduced libido and erectile dysfunction.

Finasteride, which keeps testosterone from converting into a more active form, has been used since 1992 to treat benign prostatic hyperplasia, or enlarged prostate, a condition unrelated to prostate cancer. The drug shrinks the prostate and makes it easier to urinate.

Men who are now taking the drug to treat the condition are safe to continue doing so, Scardino said, as long as their doctors monitor them for signs of cancer, with blood tests and digital rectal examinations. "I wouldn't want to scare people who are already taking Proscar into stopping," he said. "I've been telling my patients, if you're on Proscar, we'll just keep an eye on things a little closer."

The same drug, sold under the brand name Propecia and administered in one-fifth the standard dose, is used to treat baldness. Men can safely continue taking Propecia, too, as long as they are careful to be checked for prostate cancer, Scardino said, noting that most men who take this drug are under 55.

Although the researchers do not know why the finasteride group ended up with more high-grade cancers, they speculate that the drug might clear the way for the growth of tumors that are less dependent on testosterone, and that such tumors can be more aggressive.

"We need more research to determine the reasons for the increase in the number of high-grade cancers," said Joseph Smith Jr., head of urologic surgery at Vanderbilt University Medical Center, in Nashville, Tennessee.

Prostate cancer is the second most common form of cancer, after skin cancer. An estimated 220,900 cases will be diagnosed in the United States this year, according to the American Cancer Society, and 28,900 men will die of the disease. Doctors have traditionally focused on diagnosing and treating the disease early, and have only recently turned their attention to finding ways to prevent it.

Are we putting ourselves at an increased risk for Prostate Cancer?