Don't be shocked if your doctor asks you to spit into a cup during a checkup in the near future. A new study shows that a simple saliva test can detect cancer of the mouth and throat at its earliest stages, even before symptoms develop.

The test looks for distinct genetic differences in saliva and is over 90 percent accurate in detecting oral cancer, says David T. Wong, DMD, DMSc, associate dean of research at the UCLA School of Dentistry and the Jonsson Comprehensive Cancer Center.

His team has already shown that the approach has similar predictive powers for head and neck cancers. And now they're testing the saliva screen in breast cancer patients as well.

"In the future, one drop of saliva could be screened for all sorts of diseases, not just cancer," Wong tells WebMD. "Unlike tests that require drawing blood, a saliva test is totally noninvasive."

The findings were presented at the annual meeting of the American Association for Cancer Research.

Genetic Fingerprint Points to Cancer

Analyzing markers in saliva, blood, or other body fluids that signal early cancer has long been a goal of scientists seeking quick, easy, and reliable screening tests that can be done in a doctor's office.

Many researchers have focused on detecting the proteins produced by cancers. But Wong's team decided to look at gene patterns -- or genetic fingerprinting.

It wasn't easy developing the test. The breakthrough came only about three years ago, when engineers developed high-tech, highly sensitive sensors that can detect molecules at minute levels, he says.

The new study shows that distinct gene patterns are not only measurable in saliva but can also indicate a developing tumor, he says.

The test showed that saliva contains 3,000 genes. However, Wong's team shows that four of them are enough to pinpoint oral cancer.

Saliva Reveals Cancers Accurately

The study included 64 people with oral cancer and 64 people without cancer.

The presence of four genetic markers (defining a pattern) predicted with 91 percent accuracy whether a saliva sample was from a person with oral cancer or a person without it, Wong says.

Then, the researchers looked at the genetic profile in the participants' blood.

The researchers found a similar pattern for oral cancer in blood as well. "But the accuracy was only 88 percent. At least for oral cancer, saliva has a slight edge over blood testing."

By 2007, the researchers hope to identify genetic signatures for at least 10 common diseases, including other cancers, heart disease, and diabetes, Wong says.

Experts Welcome Early Detection Saliva Test

John Mendelsohn, MD, president of the University of Texas M.D. Anderson Cancer Center in Houston and moderator of a news conference to discuss the study, says the findings are encouraging.

Being able to predict who will respond to a particular treatment is becoming more and more important, as many of the new targeted cancer drugs are very selective -- not to mention expensive, he says. Plus, catching cancer early saves lives.

"A test like this meets both these goals," Mendelsohn tells WebMD. And there's a real edge over other tests in development. "Spitting is a lot easier than giving blood or dragging a stool sample to the doctor," he says.

By Charlene Laino, reviewed by Brunilda Nazario, MD

SOURCES: 96th Annual Meeting of the American Association for Cancer Research, Anaheim, Calif., April 16-20, 2005.

David T. Wong, DMD, DMsc, associate dean of research, University of California, Los Angeles, School of Dentistry, Jonsson Comprehensive Cancer Center. John Mendelsohn, MD, president, University of Texas M.D. Anderson Cancer Center, Houston.