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Spit Tests May Someday Catch Cancer

Saliva analysis detected nine of 10 oral cancers in study

TUESDAY, April 19, 2005 (HealthDay News) -- The day may come when patients will spit in the doctor's office, and no one will be offended.

That's because researchers have designed a test based on human saliva that may detect oral, breast and other cancers in their very early stages.

How soon before such tests are reality? "My prediction for oral cancer tests is a year to a year-and-a-half," said senior investigator Dr. David T. Wong, a professor and associate dean of research at the UCLA School of Dentistry and the Jonsson Comprehensive Cancer Center, in Los Angeles. For breast cancer testing, he said, it will be longer, because that research is not as far along.

A spokesman from the American Cancer Society, who is familiar with the research, said that more study is needed before the tests can be expected to be in widespread use, however.

Wong's team will present their findings Wednesday at the American Association for Cancer Research, in Anaheim, Calif.

In the study, genetic "biomarkers" isolated in saliva predicted oral cancer in about nine out of 10 cases. A biomarker, Wong said, is a kind of genetic "fingerprint" for the disease. "These 'fingerprints' occur in a totally noninvasive fluid, saliva," he said.

Wong's team isolated the genetic material, called messenger RNA, from saliva to evaluate whether it might have diagnostic value for detecting cancer in its earliest stages. Messenger RNA's job is to carry a copy of the genetic code of DNA -- housed in the nucleus of the cell -- to other parts of the cell for purposes of protein manufacture. The scientists looked for patterns or changes in this mRNA that might predict cancer.

Overall, the researchers collected saliva and blood samples from 32 patients with oral cancer, 40 patients with breast cancer, and from the same number of healthy controls. They then compared samples from each group, looking for telltale patterns or changes in the mRNA.

"In saliva," said Wong, "there are 3,000 different mRNAs. But only four [patterns] predict oral cancer. We don't know [yet] how many predict breast cancer."

"There are patterns of mRNA for oral cancer, and now we are discovering the pattern for breast cancer," Wong said. As the cancer grows, he said, "there is a significant pattern in the saliva of these individuals with oral cancer." Work on breast cancer is not as advanced, he added.

Both the saliva and the blood samples held clues to help detect cancer, but the saliva sample was a better predictor for both forms of cancer, Wong noted.

Another expert familiar with Wong's work called the approach very novel. "Many researchers are looking at DNA molecules," said Paul Denny, professor of diagnostic sciences at the University of Southern California's School of Dentistry. "Most research involving biomarkers is looking at DNA molecules or protein." Focusing on the messenger RNA is more unusual in cancer research, Denny said.

The research, Denny added, "really opens up the door for early diagnosis." And, he added, for cancer, "the earlier the diagnosis, the better."

Someday, he speculated, a doctor may routinely ask a patient to spit into a cup, then send that saliva sample to the lab for analysis, looking for numerous diseases based on changes at the molecular level.

If additional research bears out, the results from the saliva tests could be back in 30 minutes, Wong said.

Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society, praised the research but cautioned that more work is needed.

"This is interesting, it is certainly hopeful, and appears to be a test where it is easy to get a specimen," he said. "The bottom line is, there has been a long and ongoing search for some sort of biochemical marker that can detect cancer in its earliest stage. This is not the first, and won't be the last, study."

But there is a long way to go, he added, before such tests are definitely proven effective and ready for mass use.

More information

To learn more about cancer, visit the American Cancer Society.

SOURCES: David T. Wong, D.M.D., D.MSc., professor and associate dean, research, UCLA School of Dentistry and Jonsson Comprehensive Cancer Center, Los Angeles; Paul Denny, Ph.D., professor, diagnostic sciences, University of Southern California, Los Angeles; Len Lichtenfeld, M.D., deputy chief medical officer, American Cancer Society, Atlanta; April 20, 2005, presentation, American Association for Cancer Research annual meeting, Anaheim, Calif.
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