A huge federally funded cancer-prevention study has found that
finasteride, or Proscar, a popular medicine from Merck & Co. (MRK) for the treatment of enlarged prostates and baldness, can reduce a man's chances of developing prostate cancer by 25%. Proscar was an across-the-board success in the 10-year clinical trial: It worked equally well for men at both high and low risk of developing prostate cancer. Age, race, ethnicity, or family history had no affect on the drug's ability to prevent the disease.
The results were so convincing that the researchers ended the trial a year ahead of its scheduled finish in May, 2004, and they issued a strong recommendation. "Finasteride is the first drug to reduce the risk of prostate cancer," Dr. Ian Thompson of the University of Texas Health Sciences Center, director of the study, said in a statement. The study originally enrolled 18,800 men age 55 and older over a three-year period. But when results were analyzed for the first 9,000 to join the trial, the researchers decided the results were so convincing that they ended they study early and alerted the other 10,000 about the results.
The researchers also have some caveats. Men who developed prostate cancer while taking Proscar were more likely to have fast-spreading cancers than those found in the general population, But more than 97% of the men in the study who developed prostate cancer had early-stage tumors, which have a very high cure rate. Prostate cancer is the most common cancer in men, with 220,900 new cases expected to be diagnosed this year, according to the American Cancer Society. The disease will kill about 29,000 men this year.
FOLLOWING TAMOXIFEN. The results of the Proscar trial, published in the July 24 online issue of the New England Journal of Medicine, represents a big win for the nascent field of chemoprevention -- the search for a pill that can actually prevent cancer from occurring. So far, only one prevention drug has been approved by the Food & Drug Administration, AstraZeneca's (AZN) Nolvadex, also known as tamoxifen. It was O.K.'d in 1998 for the prevention of breast cancer for women at high risk of the disease after a similar federal trial spanning five years and involving 13,000 patients. The National Cancer Institute, which funded both the tamoxifen and Proscar studies, is also backing an ongoing trial in prostate cancer prevention testing two dietary supplements, selenium and vitamin E.
Proscar, which costs from $60 to $100 a month, was first approved in 1992 for the treatment of benign prostatic hyperplasia, or BPH, a noncancerous enlargement of the prostate that can block the urinary tract. Since then the drug, under the name Propecia, has also been approved at lower doses for male pattern baldness.
In the Proscar study, coordinated by a network of cancer centers known as the Southwest Oncology Group, healthy men age 55 and older were randomly assigned to receive either 5 milligrams of Proscar or a placebo daily for seven years. Each participant was given an annual digital rectal exam and a test to measure the levels of prostate-specific antigen (PSA), a marker for prostate cancer. They also had a prostate biopsy after seven years.
TUMOR ALERT. By the time the study ended this March, prostate cancer had been found in 18% of the men on the drug, or 803 out of 4,368 participants. Of the men on placebo, 24%, or 1,147 men out of 4,692, were diagnosed with the disease. More men taking Proscar experienced sexual side effects at some point during the study, while men on placebo complained more often of urinary symptoms.
The researchers noted that although the men on finasteride had
fewer prostate cancers overall, 6.4% had high-grade tumors, while only 5.1% of the men on placebo had similar growths. However, the scientists don't know if these high-grade tumors, all of which were discovered at a very early stage, will turn into aggressive cancer. Those men will continue to be followed long term.
Said Dr. Harmon J. Eyre, chief medical officer of the American Cancer Society, in a statement: "The study will no doubt prompt a lot of men to start asking their doctors whether they should be on the drug, and we would encourage men to carefully weigh their options as this information is very new." Eyre noted that "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." By Catherine Arnst in New York