About half of America's cancer patients have either tried or seriously considered turning to quack medicine for a cure, says a University of California School of Medicine physician.

"It's a lucrative $10 billion to $25 billion business, and the majority of people affected are the elderly," Dr. Jerry Lewis told the Ogden Surgical Society.Part of the reason cancer sufferers turn to non-traditional medicine is their doctors don't offer the personal attention quacks do, Lewis said.

"Discuss quackery with your patients, encourage them to participate in their own care," he urged. "Don't just tell them there is nothing that can be done."

The Davis, Calif. doctor said quackery has been around for years, and described it as the second-oldest profession.

"The first (prostitution) exploits women, and quackery exploits sick people, and both are lucrative and likely to continue being around for a long time," Lewis said.

Quack doctors generally rely on unsubstantiated treatments; point to testimonials instead of objective data; fail to fully evaluate, examine, test or X-ray a patient; use bizarre studies to prop up claims, and seldom have the proper medical degrees.

"Did you know you doctors out there didn't have to spend all that time earning your medical degrees? There are places that sell them," Lewis said.