• 10/22/2004
  • Linda Marsa
  • The Grand Rapids Press

Because the early signs of oral cancer — white spots or red areas in the mouth — are painless and difficult to detect, diagnosis usually occurs only after the disease has reached the point of requiring aggressive, disfiguring treatments. Half of those diagnosed will die of the disease.

But a soy-derived experimental treatment is being tested that could reduce this deadly toll by stopping oral cancers from developing.

“Mortality rates haven’t changed in 40 years because we don’t have any good treatments beyond surgery and no way of preventing cancers from returning,” says Dr. Frank L. Meyskens Jr., an oncologist at the Chao Family Comprehensive Cancer Center at the University of California (Irvine) Medical Center.

Meyskens and other scientists hope if the drug proves effective, it may be used to protect against oral cancer in people who are at increased risk.

“This approach seems promising,” says Sol Silverman, a professor of oral medicine at the University of California (San Francisco) Medical School and spokesman for the American Dental Association.

About 30,000 Americans are diagnosed with oral cancer each year, and only 57 percent survive more than five years. Tobacco use is the culprit behind about 75 percent of oral cancer cases, and alcohol also is a major contributing factor.

Oral cancer is the leading cancer among men in India, and incidence rates can be as high as 40 percent in Southeast Asia, where people chew betel nuts, which contain lye, or tobacco laced with lime, both of which irritate mouth tissue.

The soy derivative, known as the Bowman-Birk inhibitor, seems to work by blocking the production of certain enzymes that can prompt cells to turn cancerous. (Scientists had noticed people whose diets were rich in soybean products had a lower incidence of cancer, which prompted studies of soy’s chemical constituents.)

A 1999 study of 32 patients with leukoplakia, a potentially precancerous disease of the mouth in which white patches form on the tongue and inside the mouth, was promising. Volunteers took a twice-daily dose of the soy derivative in a mouth rinse, which they swished around their mouths and then swallowed. After a month, there was an overall 24.2 percent decrease in lesion size.

“In a couple of patients, the lesions were completely gone, which we found very encouraging for such a short study,” Meyskens says.

Researchers are in the midst of a longer study of 130 patients. Half receive a placebo, while the remainder take the drug for as long as two years to determine whether it can completely eradicate lesions and protect against recurrences of the precancerous condition.

If it works, the next step is to test it on people with head and neck cancers, which have high rates of recurrence.

“Right now, these patients have no preventive options,” Meyskens says.