Public Health Sciences Division researchers played a key role in a nationwide study that shows a daily dose of the drug finasteride (Proscar) significantly reduces a man's chance of developing prostate cancer.
The prostate cancer prevention trial (PCPT), a 10-year, nationwide study conducted by the Southwest Oncology Group (SWOG), found that men age 55 and older who took the drug had a 25 percent lower prevalence of prostate cancer compared to men who took a placebo.
But researchers also found finasteride associated with a small but significant increased risk-6.4 percent in drug users compared to 5.1 percent in the placebo group-of a particularly aggressive form of prostate cancer.
The findings appear in today's print edition of the New England Journal of Medicine and were posted in June on the journal's Web site. Co-authors include Phyllis Goodman, Dr. Catherine Tangen, Susie Carlin and Dr. John Crowley, all members of SWOG's Statistical Center, which is housed jointly within PHS and Cancer Research and Biostatistics and directed by Crowley.
"These are exciting results," Tangen said. "I think the take-home message from the study is that men should be optimistic but stay tuned for more information as additional studies are completed."
Despite concerns that have been expressed over the drug's possible risk, Crowley said that the study overwhelmingly shows that finasteride can prevent prostate cancer, the most common cancer in men other than skin cancer.
"Men who think they are at considerable risk for developing prostate cancer may want to talk with their doctors about whether they would benefit from taking this drug," he said.
Functions of finasteride
Finasteride interferes with the conversion of testosterone to dihydrotestoserone, a hormone that stimulates the growth of prostate tumors. The drug has been prescribed for the last decade as a treatment for men with enlarged prostates and is also dispensed, in lower doses, as a treatment for baldness under the brand name Propecia.
The PCPT study, funded by the National Cancer Institute, involved 18,882 healthy men age 55 and older who were free of prostate cancer as determined by digital-rectal examination (DRE) and prostate-specific-antigen, or PSA, test. Half of the men were assigned randomly to a group that received a daily dose of finasteride, while the other half received a daily placebo. Incidence of cancer was monitored by yearly physical checkups that included DRE and PSA testing. After seven years, all participants were asked to undergo a prostate biopsy to test for the presence of cancer.
Many cancer experts question whether a significant number of men diagnosed with prostate cancer receive unnecessary treatment, since many prostate tumors never cause clinical symptoms. For that reason, Tangen said that a drug that prevents such tumors from ever forming could be of enormous benefit.
"Regardless of whether or not the cancers require medical intervention, many men go through the fear, stress and expense that accompany cancer diagnosis and treatment," she said. "Finasteride could reduce the number of men who must live through that experience."
Future SWOG biological studies will examine tumor biopsies and blood samples of the participants. These studies should provide additional information about the nature of the aggressive tumors and identify subsets of men who are more or less likely to benefit from taking finasteride.
The study, which began in 1993, was slated to run through May 2004. On March 3 of this year, the Data and Safety Monitoring Committee, an independent body that periodically examined the study, advised that the trial be closed early. The recommendation came because data already collected were sound, and the conclusions were extremely unlikely to change with the addition of more data.
The SWOG Statistical Center played an integral role in the study, which involved 219 clinical sites nationwide. More than 750 men participated from the state of Washington, including more than 500 from Seattle/Tacoma. Local participating sites included Virginia Mason, the University of Washington, Swedish Hospital Medical Center and Madigan Army Medical Center.
Goodman said that at the time of its inception, PCPT was the first large study to collect and process participant data entirely using an image-based system. The SWOG Statistical Center received and processed more than 4 million pages of faxed data during the trial and provided training to research staff at more than 200 study sites nationwide through semi-annual workshops, newsletters and videos.