Office of Public Relations — Newsroom
For Immediate Release
Contact: Tonya Ewers, 303-724-1524, tonya.ewers@uchsc.edu
Finasteride Unlikely Cause of High-Grade Prostate Cancer
AURORA, Colo. (Sept. 11, 2007) – It is unlikely that the drug finasteride causes high-grade prostate cancer, according to a group of researchers from the Southwest Oncology Group (SWOG). Rather, the drug’s gland-shrinking effect may make it easier for doctors to find aggressive cancer during biopsy.
The findings are published in the Sept. 19, 2007, issue of the Journal of the National Cancer Institute. Dr. M. Scott Lucia, associate professor of pathology, director of the Prostate Diagnostic Laboratory, co-director of the Prostate Cancer Research Laboratories and chief of Genitourinary and Renal Pathology at the University of Colorado at Denver and Health Sciences Center, is the paper’s lead author.
In 1993, more than 18,000 men at risk for prostate cancer joined a nationwide study to determine if taking a daily 5 mg dose of the 5 alpha-reductase inhibitor finasteride versus placebo would reduce the risk of prostate cancer. The Prostate Cancer Prevention Trial’s results, published in the New England Journal of Medicine in 2003, showed that the drug reduced the incidence of prostate cancer diagnosis by 25 percent in men who took it, compared to those who took the placebo, indicating that the drug did seem to prevent diagnosis of prostate cancer. However, there was a twist.
“Although the risk for prostate cancer dropped overall, it appeared that men were actually at increased risk of getting an aggressive (or high grade) cancer while taking the drug,” Lucia said. “That became a major problem for this drug if it was to be used in a prevention setting.”
Lucia and a team of researchers from cancer centers across the country compared tissue samples from prostate glands removed from men in the study. If the drug caused high-grade cancer, they would have seen more advanced high-grade cancer in the men taking finasteride than in those taking placebo. But they didn’t. In fact, the tumors in men taking the drug were less advanced than those taking the placebo.
“We cannot say without a doubt that the drug does not cause aggressive cancer, but it is less likely than originally thought,” he said. “This news should lessen fears of men who take finasteride and drugs like it for benign prostatic hyperplasia.”
Perhaps, the researchers thought, finasteride changed the structural appearance of cancer under the microscope by altering a certain hormone, as similar drugs did, making low-grade cancer appear to be a more aggressive type. But there was no difference between the appearance of tumors of those taking the drug versus the placebo.
So if there was no evidence the drug caused tumors to grow or caused the tumors to falsely display characteristics of aggressive cancer, why did the men in the Prostate Cancer Prevention Trial seem to have more diagnoses of aggressive cancer? Maybe the drug made it easier for doctors to find cancer in the prostate.
Biopsying the prostate to find cancer is truly searching for a needle in a haystack, Lucia said. If the prostate is large and the tumor is small, doctors have a smaller chance of hitting the tumor with a needle. But if the prostate is small, doctors have a better chance of hitting a tumor with the biopsy needle. Using biopsy to grade prostate cancer is an even more inexact science, he added.
Finasteride kills low-grade prostate cancer cells but has little affect on high-grade cancer cells; the Prostate Cancer Prevention Trial proved that. Finasteride also shrunk the prostate by an average 18 percent during the first year, and an average 25 percent over seven years. If the drug left the aggressive cells behind and shrunk the gland at the same time, it was more likely that a biopsy needle would hit the tumor.
The most accurate way to grade prostate cancer is to remove the prostate and examine the tumor, called prostatectomy. When the researchers compared how accurately the biopsy graded a tumor compared to prostatectomy, they found that the biopsy accurately detected high-grade cancer only 50 percent of the time in the placebo group. But in the finasteride group, the biopsy grading detected 70 percent of the high grade cancers.
“Shrinking the prostate using this drug can actually result in earlier diagnosis of high-grade prostate cancer,” Lucia said.
While he thought it unlikely that the cancer community would embrace finasteride as a global preventive tool, Lucia hopes the results of the SWOG study will give men at high risk of prostate cancer a new option for both prevention and diagnosis.
“A negative biopsy doesn’t mean you don’t have cancer, it means it could be there but we didn’t find it,” he said. “I hope the results of this study open up a door for discussion with patients who are at high risk of cancer about going on this drug to both prevent them from getting cancer and to shrink the gland so it is easier to find cancer if it’s there.”
The University of Colorado Cancer Center is the only National Cancer Institute-designated comprehensive cancer center in the Rocky Mountain Region. Headquartered primarily at the University of Colorado at Denver and Health Sciences Center, its four-part mission is excellence in cancer research, treatment, prevention and education. For more information, visit the Web site at http://www.uccc.info.
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