For decades, physicians have known that male hormones fuel prostate cancer growth. That's why therapies that block the production of androgen - or testosterone - provide some of the most effective treatments for men with advanced prostate cancer. Certain drugs, for example, cause the tumor to shrink and PSA levels to decline. But despite initial success with therapies that block testosterone production, prostate tumors inevitably return and are resistant to further treatment.

Now, research conducted by Memorial Sloan-Kettering Cancer Center investigators sheds new light on why existing therapies don't stop the disease from returning. The findings, published in the November 3rd issue of the Journal of the National Cancer Institute, challenge current thinking about how to treat prostate cancer. The study dovetails with recent research also published by Memorial Sloan-Kettering investigators that offers new strategies to treat this lethal form of the disease.

In the current study, investigators at Memorial Sloan-Kettering evaluated the effectiveness of hormonal therapy to treat human prostate cancer in mice. They found that withdrawing testosterone caused the majority of the tumor cells to go into a dormant, or growth arrested state, but that very few cells died.

"Until now we thought that blocking the production of testosterone killed most of the prostate cancer cells and that the few remaining "resistant" cells were what caused the disease to recur. But this study suggests that few cells die after testosterone is blocked," said Dr. Howard Scher, Chief of Genitourinary Oncology at Memorial Sloan-Kettering Cancer Center and senior author of the study in the Journal of the National Cancer Institute.

To determine why therapies that block the production of testosterone ultimately fail to prevent a recurrence of prostate cancer, the researchers injected mice with human prostate cancer cells and once the disease had developed, withdrew testo
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Contact: Kelli Stauning
publicaffairs@mskcc.org
212-639-3573
Memorial Sloan-Kettering Cancer Center
1-Nov-1999