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Herbal Mixture May Protect Against Prostate Cancer Clinical Trial of 'PC-SPES' Moving Forward By Joyce Frieden Reviewed by Gary D. Vogin, MD Aug. 31, 2000 -- A combination of eight Chinese and American herbs has been shown in animal studies to reduce the number of new cases of prostate tumors by up to 40%. The mixture, called PC-SPES, is sold as an over-the-counter powdered food supplement and contains isatis, licorice, lucid ganoderma, pseudo-ginseng, rubescens, saw palmetto, and scute. "PC-SPES is a very interesting mixture, and [we need] more patients to enroll in clinical trials" of the preparation, says Jan Geliebter, PhD, who spoke on the subject at a recent Washington, D.C., press conference sponsored by the American Institute for Cancer Research. In addition to reducing the occurrence of tumors, PC-SPES also lowers many patients' level of prostate-specific antigen (PSA), a protein produced by the prostate gland. A high PSA level is a possible indicator of prostate cancer. Well over half of patients taking PC-SPES see a decrease in PSA to a nearly undetectable level, says Geliebter, an assistant professor of microbiology and immunology at New York Medical College, in Valhalla, N.Y. Geliebter and his fellow researchers conducted a series of studies to find out whether the lower PSA levels brought about by PC-SPES would result in a lower incidence of cancer. In one study, rats were injected with a dose of cancer cells that usually cause deadly tumors. The same rats were also fed diets supplemented with PC-SPES. In that test, 40% of the rats did not develop any tumors. To date, studies in humans have been on too small a scale to draw conclusions from, he says. Researchers think PC-SPES works by mimicking the action of estrogen, a female hormone. "There is no estrogen in PC-SPES, but its estrogenic effects may play a role in its results," says Geliebter. It also plays a role in some unwanted ways, by causing side effects such as nipple tenderness and breast enlargement, Geliebter says. The preparation's most serious side effect is blood clotting, which has been reported in a very few patients. PC-SPES does appear promising, says Glenn Bubley, MD, director of genitourinary oncology at Harvard Medical School and Beth Israel Deaconess Medical Center, in Boston. Bubley says he has recommended it to some of his patients for whom hormone therapies didn't work. Hormone therapies are the first line of treatment in prostate cancer, he says, but when they don't work, he now tries PC-SPES before resorting to chemotherapy or other aggressive forms of treatment. Bubley is currently involved in a study comparing PC-SPES to a drug called diethylsilbestrol (DES). "DES was the first drug prescribed for prostate cancer in 1950," he says. "We got rid of it because it caused blood clots. We need to know that PC-SPES is not just garden-variety DES." There are several practical problems in conducting a clinical trial with an over-the-counter preparation such as PC-SPES, which costs about $400 per month, Bubley says. Normally, a drug company trying to get a new drug approved for the market will supply an expensive drug for free. But PC-SPES is already on the market -- and the company distributing it is "making more money than God," Bubley says -- which lessens its interest in giving away samples for a clinical trial. And if the results are unfavorable to PC-SPES, the company may very well lose money. On the other hand, study investigators cannot ask patients to pay for such an expensive drug themselves. "At Harvard, we can't get a study approved by the institutional review board if the patient has to pay for the medication," he says. "That would be a study for the rich, and that's unethical." The Harvard researchers finally managed to convince the company to give them some free PC-SPES, enabling the study to go forward. One thing the researchers are hoping to find out is what the correct dosage should be. "If PC-SPES had gone through the normal drug development process, we would know what the optimal dose is, but as far as I can tell, no one has a clue," Bubley tells WebMD.
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