"While both implants were extraordinarily successful at preventing major long-term complications, Palladium-103 was superior to Iodine-125 in preventing moderate long-term complications by 13 percent," said Richard Peschel, M.D., professor of therapeutic radiology at Yale School of Medicine. "Our study is the first to compare prostate cancer implant therapies, and the results could lead to improved outcomes for patients."

In the seven-year study, Peschel and his team also found that the minimum dose for Palladium-103 could be increased without increasing side effects. This increased dose has the potential for improving cure rates, Peschel says

Published in the Oct. 29 issue of Radiation Oncology Investigations: Clinical and Basic Research, the findings are significant for men facing a treatment decision for prostate cancer.

When diagnosed with prostate cancer, most men are presented with two treatment options: radical surgery and implant therapy, which involves placing 75 to 100 small radioactive seeds throughout the prostate using a one-time, minimally invasive procedure. Implant therapy is an increasingly popular choice because it is a cheaper, simpler out-patient procedure that involves far less recovery time, a lower complication rate and cure rates that are equivalent to radical surgery.

For 10 to 15 years, Iodine-125 was the most frequently prescribed implant treatment, but newer therapies have emerged, including Palladium-103. Prostate cancer implant programs using either Iodine-125 or Palladium-103 radioactive seeds have been extremely successful in treating early prostate cancer. About 30,000 prostate implants will be performed in the United States in the year 2000.

The research included an analysis of the potential long-term side effects that are predicted using a modern radiobiology model of the effects of implant therapy on normal tissues, such as the bladder and rectum. The model predicted that Iodine-125 would produce more long-term side effects than Palladium-103, a prediction that mirrors the clinical results. Side-effects can include inflammation of the urethra and inflammation of the rectum or anus.

Prostate cancer is the most commonly diagnosed cancer and the second most common cause of death in American males. With prostate- specific antigen (PSA) screening programs, the majority of prostate cancers can be detected early, when the cancer can still be cured with local therapies such as radical prostatectomy or prostate implant.

Peschel's research team at Yale included Zhe Chen, assistant professor of therapeutic radiology; Kenneth Roberts, associate professor of therapeutic radiology; and Ravinder Nath, professor and chief of radiological physics.