Scientists Report New Diagnostic Test for Cancer : Medicine: Markers of the disease are matched with cells in tissue, body fluids. Researchers hope the breakthrough will lead to earlier detection.

BALTIMORE — A diagnostic test for cancer that could revolutionize screening for the deadly disease has been developed by researchers at Johns Hopkins Medical Institutions.

The new test, reported in today’s issue of Proceedings of the National Academy of Science, identifies replication errors in DNA that occur frequently in cancer. The errors, known as clonal markers, are used as a fingerprint for cancer.

Researchers hope the breakthrough will bring a general cancer screening method to identify cases sooner than existing tests.

The researchers compare markers from several types of cancer with cells found in tissue, body fluids or secretions from a suspected cancer site. If the markers match, there is a strong indication that the patient has cancer.

“Clonal markers are a definitive indicator of cancer. If you see these markers, you know you’ve found disease,” said Dr. David Sidransky of the Johns Hopkins Oncology Center and principal investigator of the study.

Use of the test on people at high risk for bladder and cervical cancers could begin within a year, Sidransky said. He said the test could also be used to detect other cancers, including cancers of the lung, breast, colon and prostate.

“What makes this so easy is that it’s just a very simple technology,” Sidransky said. “It’s a one-step thing. The whole thing can be done in one day.”

Sidransky said he believes the test, expected to cost about $50, may become part of routine medical care, providing an easy method of detecting cancer in its earliest and most treatable stages.

However, he said the test is still in its experimental phase and must be validated through a series of larger trials, which could take years to complete. Further trials also are needed, he said, to verify that the test identifies cancer earlier than standard methods.

“But the reason we’re so confident is that even if you only detected half of all cancers--even if we fell short of expectations--you’d be detecting a lot more cancers than you are now,” Sidransky said.

Researchers also plan to use the test on cancer patients whose tumors have been surgically removed in an effort to see if the patients have any residual cancer cells.