June 25, 2003 -- On Tuesday, the National Cancer Institute (NCI) announced the early termination of the Southwest Oncology Group Prostate Cancer Prevention Trial (PCPT), which found that the 5-alpha-reductase inhibitor finasteride reduced prostate cancer risk by 25%.
The study was released Tuesday online by the New England Journal of Medicine, and it will be published in the July 17 print issue.
While finasteride is the first drug found to reduce the risk of prostate cancer, researchers cautioned that not all the news from the NCI-funded trial was positive. Men taking finasteride had fewer prostate cancers overall compared with men in the placebo group (18% vs. 24%), but more high-grade tumors were seen in patients receiving active treatment. Thirty-seven percent of the tumors in the finasteride group were high grade vs. 22% in the placebo group.
The negative finding did not appear to dampen the enthusiasm of officials with the NCI and the American Cancer Society (ACS). In a press statement, Leslie Ford, MD, the NCI Division of Cancer Prevention associate director for clinical research, noted that "PCPT and its findings mark a milestone for the field of cancer prevention, and we will continue to learn more in the years to come."
The ACS released a statement calling the study, "a major step forward, providing the first clear evidence that chemoprevention of prostate cancer can work.
"The study will no doubt prompt a lot of men to start asking their doctors whether they should be on this drug, and we would encourage men to carefully weigh their options as this information is very new," the statement read. "There are still some important unanswered questions, especially regarding side effects, whether it can benefit men at increased risk, especially African Americans..., and the mechanism by which men taking the drug develop higher-grade tumors."
Lead researcher Ian M. Thompson, MD, of the University of Texas Health Science Center, told Medscape that it is too soon to say whether the increase in high-grade tumors seen in the trial truly represents a more aggressive disease course. He adds that it is not yet clear whether chemopreventive treatment with finasteride will have an impact on prostate cancer deaths.
He does not foresee the drug being used in all men at risk for prostate cancer, but says he would recommend it to patients who are especially concerned about developing the disease.
"This is the patient who is probably already having an annual [prostate-specific antigen] test," he said. "If we can offer that man an intervention that can reduce his risk of being told that he has prostate cancer by 25%, that would have a significant public health impact."
The double-blinded study involved healthy men, aged 55 years and older, randomized to take finasteride or placebo daily for seven years. All of the men had normal digital rectal exams and American Urological Association symptom scores of less than 20 at recruitment.
The trial was originally scheduled to end in May 2004, but in March of this year an independent examining board voted to close it early on the strength of the data already collected.
In an editorial accompanying the study, Peter T. Scardino, MD, chief of urology at Memorial Sloan-Kettering Cancer Center in New York City, concluded that the drug, "does not seem to be an attractive agent for the chemoprevention of prostate cancer."
In an interview with Medscape, Dr. Scardino said the aggressive cancer detection methods used in the study make it difficult to determine if the identified tumors were clinically meaningful.
"We have no reason to believe that these tumors posed any real threat to life or health," he said. "On the other hand, there is a very real chance that (by taking this drug) a man would develop a high-grade cancer. That doesn't sound like a very good tradeoff to me."
Dr. Scardino said he would like to see studies evaluating the chemopreventive potential of finasteride in younger men.
"This study does tell us that preventing prostate cancer by manipulating androgen levels in the prostate is a reasonable possibility, but it doesn't prove that it works," he said. "And it certainly does not seem prudent at this point to tell tens of thousands of men that they should take this drug."
N Engl J Med 2003;349:213-222, 295-297
Reviewed by Gary D. Vogin, MD
Medscape Medical News © 2003
Cite this: Salynn Boyles. Finasteride Reduces Prostate Cancer Risk - Medscape - Jun 25, 2003.