Hopkins seeks saliva test for mouth, throat cancers Dentists could perform new screening method

March 30, 1998|By Jonathan Bor | Jonathan Bor,SUN STAFF

Someday, getting screened for cancers of the mouth and throat could start with spitting into a cup.

Researchers with the Johns Hopkins Oncology Center reported progress yesterday toward a simple and inexpensive test that would find genetic evidence of these cancers in saliva. The evidence would come from cells that slough off from tumors, including those too small to produce symptoms or detect through conventional means.

Dr. David Sidransky, a Hopkins cancer researcher, said the screening method would be of particular value to people who smoke, chew tobacco or drink alcohol -- habits that account for almost all of the 40,000 cancers of the mouth and throat that occur each year in the United States.

"We're looking at the possibility for a simple saliva test being able to diagnose a very deadly cancer in its early stage, its most curable form," Sidransky said. "This is an easy test from the point of view of a patient -- easy to do with very high compliance."

The test could be offered by dentists, who would take saliva and blood samples and submit them to a laboratory equipped with the necessary genetic probes, Sidransky said. Many dentists already take part in the fight against oral cancers, routinely looking for suspicious lesions on the gums, lips and tongue.

Sidransky discussed his research at the annual meeting yesterday of the American Association of Cancer Research in New Orleans.

Mouth and throat cancers are particularly deadly because they often do not cause symptoms until the tumors are too large to cure. Often, patients feel well until they have trouble swallowing or have mysterious ear pain that cannot be tied to ordinary infections.

Looking for 'junk DNA'

"A lot of these tumors became very advanced before they can be detected," said Dr. Michael F. Spafford, a Hopkins head and neck surgeon involved in the research. "These are people who have to have parts of their tongue, jawbone or larynx removed."

Overall, the survival rate is about 50 percent.

The test looks for strange repetitious patterns in genetic sequences that are sometimes known as "junk DNA." The sequences do not play any direct role in the patient's cancer, but can serve as markers that cell growth is spiraling out of control in a cancerous cycle.

Scientists compare a patient's blood and saliva.

The genetic sequences seen in the blood are considered normal; differences seen in the saliva are evidence of cancer.

Cancer markers

Hopkins researchers studied patients undergoing surgery for mouth and throat cancers. They found cancer markers in the saliva of 80 percent of them.

Sidransky said he hopes to refine the test so it can identify the cancers in more than 90 percent of such cases.

The test would then be sensitive enough to screen people with no previous diagnosis of cancer.

Monitoring recurrence

The Hopkins group is using the test experimentally to see whether cancerous tissue is left behind after surgery or if the cancer has spread in the months that follow.

"We're going to continue to check saliva as patients go through treatment to see if they have recurrence, which can be as high as 50 percent in this group of patients," Spafford said.

The Hopkins group is using the same technology to develop screening for other cancers in body fluids. Researchers hope to screen urine for bladder, prostate and kidney cancers.

The tests probably would cost about $150, Sidransky said.

"Potentially, this test could be used to screen for any cancer where a bodily fluid or secretion can be obtained," he said, including cancers of the colon, breast and ovaries.

Pub Date: 3/30/98

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