Prostate cancer research may be faster with prostate-specific antigen endpoints

A new study from Columbia University Medical Center researchers at NewYork-Presbyterian Hospital/Columbia, who are members of the Southwest Oncology Group (SWOG), suggests that certain changes in prostate-specific antigen (PSA) levels may serve as surrogate endpoints for prostate cancer survival.

Researchers looking to speed up the process of clinical trials have suggested that these biomarkers could be used to measure treatment efficacy.

Currently, the U.S. Food and Drug Administration accepts only survival as an endpoint of measure. Survival as a primary endpoint was used in phase III studies of novel chemotherapeutic drugs for men with androgen-independent prostate.

Daniel P. Petrylak, M.D., associate professor of medicine at Columbia University College of Physicians & Surgeons and director of the genitourinary oncology program at NewYork-Presbyterian/Columbia, together with his research team, retrospectively analyzed results of 551 men with prostate cancer treated in the Southwest Oncology Group Protocol S9916. By reviewing the clinical trial, it was noted that there were several different changes in PSA levels, which could possibly serve as surrogate endpoints for survival.

The authors observed that the risk of death, in men whose serum PSA levels declined by at least 30 percent in the first three months of treatment, was reduced more than 50 percent. Findings are published in the Journal of the National Cancer Institute (April 19, 2006 issue).

"The findings show that PSA levels can be a reliable endpoint measure of prostate cancer treatment efficacy," said Dr. Petrylak, lead investigator. "However, this and other candidate surrogate endpoints must be validated in independent clinical trials of men with prostate cancer."

This study is a follow-up to a landmark phase III trial published in the New England Journal of Medicine (Oct. 7, 2004), by the same Columbia University Medical Center and NewYork-Presbyterian Hospital/Columbia research team, who are members of SWOG, one of the largest cancer clinical trials cooperative groups in the United States. The study found that men with androgen-independent (hormone-refractory) metastatic prostate cancer who were treated with the chemotherapy drug Taxotere. (docetaxel) Injection Concentrate in combination with the drug estramustine survived 20 percent longer than similar patients receiving the standard therapy.

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