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• No proof it slows disease
• Book popularized treatment
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(AP) -- Shark cartilage, often touted as a cancer cure, has proved worthless in the first careful scientific study in people with advanced tumors.

Doctors estimate that 50,000 U.S. cancer victims have tried shark cartilage, either alone or with standard drugs.

This and dozens of other herbs and potions sold as dietary supplements have proliferated since 1994, when Congress exempted them from regulation by the Food and Drug Administration.

Recently, however, doctors have attempted to subject some of these alternative therapies to the same rigorous testing that the FDA demands of prescription drugs to make sure they are safe and valuable.

The latest study, conducted and largely financed by the independent Cancer Treatment Research Foundation in Arlington Heights, Illinois, tested shark cartilage powder on terminally ill cancer patients and found it did nothing to slow their disease or improve their quality of life.

"It doesn't work," said Dr. Denis R. Miller, who directed the study.

The results were published in the November issue of the Journal of Clinical Oncology.

The three-month study was conducted on 60 patients with cancer of the brain, breast, lung, colon, prostate, bladder or lymph system. In no case did patients' tumors go away or even shrink.

In 10 of the patients, tumors temporarily stopped growing for periods ranging from three to 10 months. However, Miller said this would be expected in any group of advanced cancer patients, even if they got no treatment.

"Shark cartilage by itself won't result in any measurable clinical response," Miller said. "It won't improve quality of life. As a single agent, it has no role in treating cancer."

Shark cartilage's wide use for cancer resulted in part from William Lane's book "Sharks Don't Get Cancer." Lane Labs, headed by Lane's son Andrew, makes the BeneFin brand of shark cartilage.

"We definitely have seen it work in some people with cancer. There's no doubt about it," said Andrew Lane.

He criticized the study for taking people off treatment too soon and for using what he considered to be an inferior brand of shark cartilage. He said his company is sponsoring three new studies of shark cartilage on 60 victims of brain and breast cancer.

Barrie Cassileth, a psychologist who wrote "The Alternative Medicine Handbook," said shark cartilage's popularity as a cancer treatment has already peaked. But it remains widely used for joint problems, against which it also has no proven benefits.

She said that while few doctors ever believed that it cured cancer, "the benefit of this article is that it documents for the general public the uselessness of this over-the-counter food supplement."

Dr. Patricia Ganz of the University of California at Los Angeles said she is glad to have clear data she can give to desperate cancer patients who ask her about shark cartilage.

"In advance disease, when the medical community says we don't have much to offer you, people are looking for anything that will give them hope," she said.