National Study Finds Drug Prevents Prostate Cancer in Some Men
06/24/03 Portland, Ore.
Almost 600 Portland-area men and three local health and research institutions participated
Men who took a drug that affects male hormones reduced their chances of getting prostate cancer by nearly 25 percent compared with men who took a placebo, according to the results of a study released today online by the New England Journal of Medicine.
Portland research and health institutions Kaiser Permanente's Center for Health Research, Providence Health System and Oregon Health & Science University Cancer Institute were three of approximately 220 Prostate Cancer Prevention Trial (PCPT) study sites around the nation. Some 588 men in the region participated in PCPT, the largest, longest prostate cancer prevention study ever conducted in the United States. With 297 participants, the OHSU Cancer Institute was the 10th largest contributor of participants to the study in the nation. Providence Health System had 262 participants and the Center for Health Research had 39 participants.
The study data also suggest a note of caution. Although study participants taking the drug, known as finasteride, had fewer cancers overall, they had a greater number of high-grade prostate cancers. In the entire group of men taking finasteride who were evaluated, 6.4 percent had high-grade cancers compared with 5.1 percent of men evaluated in the placebo group had high-grade cancers.
Researchers are studying several possibilities to explain why some men on finasteride had more high-grade tumors. The drug affects the appearance of prostate cancer cells, and this may lead to a false estimate of tumor grade, which is determined visually by a pathologist. Another explanation being examined is whether finasteride truly causes more aggressive tumors to develop - either by preventing only low-grade tumors, or by making the prostate gland more favorable to aggressive tumors.
Prostate cancer is the most common malignancy among men and the second leading cause of cancer death in men in the United States. Overall, roughly one in six American men will develop prostate cancer during his lifetime -- a greater proportion than women who will develop breast cancer over a lifetime.
The American Cancer Society (ACS) estimates that 3,200 men in Oregon and 3,900 men in Washington will be diagnosed with prostate cancer in 2003. More than 220,900 men will be diagnosed nationwide. Four hundred men in Oregon, 500 men in Washington and 28,900 men across the nation will die of the disease in 2003, the ACS says.
Nearly 19,000 men around the country enrolled in the PCPT, which began enrolling men almost 10 years ago. The study was originally scheduled to close in May 2004, but study findings resulted in its early closing.
Men chosen for PCPT showed no evidence of prostate cancer at the start of the trial. To enter the study, men needed to have a normal digital rectal exam and a prostate specific antigen (PSA) level of 3 ng/ml or less. These tests were repeated annually.
Study participants were randomly divided into two groups. Half took one 5 mg tablet of finasteride per day for seven years. The other half took a placebo, which is an inactive pill that looks like finasteride. Neither the participants nor the study physicians knew which men were getting finasteride and which men were getting placebo The trial design, called "double-blinding," permits researchers to see the possible benefits and side effects of finasteride without being influenced by other factors, such as the expectations of participants or researchers.
The participants also agreed to have a prostate biopsy after they had participated for seven years. At the time the trial ended, about 9,000 men had undergone biopsies.
The FDA approved finasteride in 1992 for the treatment of benign prostatic hyperplasia (BPH), a noncancerous enlargement of the prostate gland. Because BPH and prostate cancer are influenced by similar hormonal factors, researchers believed the drug might also prevent cancer. Finasteride controls BPH by reducing levels of the hormone dihydrotestosterone (DHT) in the prostate. The drug works by blocking the activity of an enzyme that converts testosterone, the primary male hormone, to DHT.
The study was coordinated by a network of researchers called the Southwest Oncology Group (SWOG) and funded by the National Cancer Institute (NCI). Another large prevention study currently under way, the Selenium and Vitamin E Cancer Prevention Trial (SELECT) is available to men in the Portland area. For more information on PCPT or SELECT, the public may call the NCI's Cancer Information Service at 800 4-CANCER (800 422-6237) for information in English and Spanish. Or visit http://www.cancer.gov/pcpt on the Web.