SELECT Completes Randomization More than Two Years Ahead of Schedule
A large-scale clinical trial to investigate whether supplementation with the antioxidants vitamin E and selenium can prevent prostate cancer has just about completed enrollment of 32,400 participants, more than two years ahead of schedule. The NCI-sponsored trial - dubbed SELECT, for Selenium and Vitamin E Cancer Prevention Trial - began enrolling patients in August 2001. Achieving the randomization goal was expected to take approximately five years. Instead, it will take approximately 34 months, with randomization set to cease on June 24.
To complete randomization of this many participants in such a short period is rarely seen, said Dr. Charles A. Coltman, Jr., chair of the Southwest Oncology Group (SWOG), which is coordinating the trial. "This accomplishment is a tribute to the men who have volunteered to participate in SELECT at a rate of 1,000 a month and to the researchers and clinical research associates who did a masterful job of recruitment."
Although it is difficult to attribute this achievement to any single factor, Dr. Coltman said, one clearly important component is that all 428 study sites - spread across 50 states, Puerto Rico, and 6 Canadian provinces - are using a Web-based system to conduct nearly every aspect of the trial, including patient registration, randomization, and ordering of supplements.
The impetus for SELECT was the results of secondary analyses from two previous studies. A secondary analysis from the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, or ATBC, published in 1998, found that vitamin E supplementation in the form of 50 mg of alpha-tocopherol daily reduced prostate cancer incidence by 32 percent and prostate cancer death by more than 40 percent in Finnish male smokers. In a much smaller trial published in 1996 to examine the impact of selenium on the risk of skin cancer recurrence, a secondary analysis found that 200 micrograms of selenium daily yielded a 63 percent reduction in prostate cancer risk.
Participants in SELECT must be 55 years or older, have a clean digital rectal examination, and a prostate-specific antigen level of less than or equal to 4.0 ng/ml. Black participants can be as young as 50, because they tend to get prostate cancer earlier. In addition, black men in the United States have the highest incidence of prostate cancer in the world. Participants are being randomly assigned to one of four treatment groups: 200 micrograms of selenium daily plus placebo, 400 mg of alpha-tocopherol daily plus placebo, 200 micrograms of selenium and 400 mg of alpha-tocopherol daily, or two placebos daily.
"SELECT is far from over," said Dr. Leslie Ford, associate director for clinical research in the NCI Division of Cancer Prevention. "We appreciate the dedication of the men participating who will continue in the study for several more years in order for us to get the true answers about the benefits and risks of selenium and vitamin E."
Such answers are vitally important. Prostate cancer is one of the most deadly forms of cancer. It is estimated that in 2004 there will be more than 230,000 new cases, and approximately 30,000 men are expected to die from the disease.
Other investigations will be conducted as part of SELECT, including those to determine the effect of selenium and vitamin E on the risk of lung and colon cancer, the genetic underpinnings of prostate cancer risk, and the associations between diet and cancer.