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Chicago--In the wake of the surprising results of the Prostate Cancer Prevention Trial (PCPT), researchers continue to investigate possible therapies for prostate cancer prevention. Some focus on alternative therapies, with a major effort underway to determine the possible efficacy of selenium and vitamin E in the form of the Selenium and Vitamin E Cancer Prevention Trial (SELECT).
Alternative therapies are important now because of their widespread utilization, and because the PCPT trial, which compared the efficacy of finasteride with placebo in preventing prostate cancer on 16,000 men, surprised the medical community with results showing lower rates but more severe grades of prostate cancer among those who took finasteride.
"There will never be another finasteride study, because it takes too long, unless the government does it. But there might have been if it hadn't been for the curveball," said Franklin C. Lowe, MD, MPH, associate director, St. Luke's Division department of urology, Columbia University, New York, who has also been chairman of AUA's alternative medicine committee for 3 years.
The Finnish study found that the supplements had mixed effects, indicating that vitamin E supplementation reduced the incidence by 32%, but beta-carotene increased the incidence by 23.5% (N Engl J Med 1994; 330:1029).
"The ATBC study looked at smokers, and there were a whole host of other cancers, such as skin cancers, involved," Dr. Lowe said at the Johns Hopkins Institute's Advances in Genitourinary Health annual meeting. "People looked at beta carotene for other cancer issues, and there seemed to be some benefit."
While alternative therapies enjoy great utilization and may play a significant role in the prevention of prostate cancer, patients need to be mindful of potential issues with quality control and contamination, Dr. Lowe said, drawing a lesson from the recent experiences with the herbal therapy PC-SPES. While PC-SPES has been proven to have anti-estrogenic effects, Dr. Lowe said, a batch was found to be contaminated, leading to the closure of the supplier in 2002.
"It was found to contain diethylstilbestrol, a synthetic estrogen, which was the classic treatment for metastatic prostate cancer prior to advent of LHRH agonists, as well as warfarin and Xanax. These medications don't grow on trees and plants, so this was a real issue," Dr. Lowe said.
The developments were disappointing, because PC-SPES had been under clinical trials.
"There were signs in the early studies that people were responding in terms of reduction of PSA levels," Dr. Lowe said.
Another source indicating that selenium may have efficacy for prevention of prostate cancer was an Arizona Cancer Center trial (JAMA 1996; 276:1957-63). When selenium was taken daily for a mean of 4.5 years, patients had an incidence of prostate cancer that was decreased by 4.5 years. When the participants were followed for 7 years, they showed a reduction in risk of developing advanced prostate cancer of between 50% and 66%.
"The trial seems to correlate that people who had low levels of selenium were more apt to have prostate cancer," Dr. Lowe said.
He noted that while many of the trials focus on the use of natural remedies in the primary prevention of prostate cancer, many patients with cancer use these methodologies for secondary prevention.