Cancer test a failure. Researchers say the CEA test commonly used for detecting the return of colon cancer should be discontinued. The main problems:

• 40 percent have false negatives, which delays cancer detection.
• 20 percent have false positives, requiring unnecessary further testing.
• Despite its cost, the test increased survival rate by less than 1 percent.

Source:Journal of the American Medical Association

TEST TO DETECT COLON CANCER DOESN'T WORK/MAYO RESEARCHERS SAY PROCEDURE UNRELIABLE, SHOULD BE ABANDONED

A common blood test used to detect a recurrence of colon cancer is highly unreliable and expensive and can lead to needless tests and even surgery on healthy patients, researchers at the Mayo Clinic and elsewhere say.

The procedure - called a CEA test - identifies a protein-like substance called carcinoembryonic antigen. The antigen may be produced in large quantities by cancer in the large bowel and can be accurately identified in blood.

But in their study, published in today's edition of the Journal of the American Medical Association, the researchers found that the test has such a low success rate that it should be abandoned.

"We found the test extremely unreliable and hope that it will be abandoned,"' said Dr. Charles Moertel, professor of oncology at the Mayo Clinic in Rochester and chief author of the study.

In a telephone interview from Alaska, Moertel said that his research team also hopes that the study stimulates a search for a better way to give colon cancer patients a second chance.

When the CEA test was developed about 20 years ago, some experts thought it could be used as a screening tool for colon cancer, the nation's second-leading cancer killer behind lung cancer. Colon cancer will kill about 57,000 Americans this year.

Although follow-up research showed that the test was too insensitive to serve as a screen, it became the standard way to monitor patients after colon cancer surgery. To determine the test's effectiveness, researchers at the Mayo Clinic, the Fred Hutchinson Cancer Research Center in Seattle, Temple University School of Medicine and the University of Pennsylvania, both in Philadelphia, and the Grand Forks Clinic in Grand Forks, N.D., followed 1,216 patients who had undergone colon cancer surgery. Of those, 1,017 were monitored by CEA testing.

"The fundamental objective of the test is to pick up a recurrence at a stage when it can be cured," Moertel said. But one-year survival rates for study participants who experienced a recurrence were 2.3 percent for those who underwent CEA monitoring and 2 percent for those who did not.

Moertel said there are two major problems with the test.

About 40 percent of patients have false negatives, which means that many colon cancers go undetected until they have spread.

About 20 percent of patients have false positives. To rule out a recurrence, they must unnecessarily endure numerous tests. And in some instances, patients with false positives also must undergo rigorous exploratory abdominal surgery at a cost of about $10,000.

"Our uncontrolled study indicates that the maximum anticipated gain from CEA monitoring will be a small number of lives saved ... probably less than 1 percent of the patients monitored,"' the authors wrote.

Moertel said about 80 percent of U.S. physicians now use the test to monitor more than 500,000 patients annually. During the normal five-year monitoring period, patients can have from 10 to 40 CEA tests, each costing about $50.

To give an idea of the costs involved, the researchers calculated that monitoring and conducting associated tests on the 1,017 patients in the study totaled nearly $1.5 million.

"No more lives are saved despite the added expense," Moertel said.

A) From what is discussed in the article. Explain whether the CEA test is accurate, inaccurate or you can't say. Then explain if it is reliable, unreliable or you can't say.

B) In the last four paragraphs the article says ". . . small number of lives will be saved;less than 1% of patients monitored." And later ". . .more than 500,000" patients are monitored each year. What role does theprecisionof the numbers play in your analysis/understanding of these statements?

C) determine aninterval estimate of the cost of using the CEA test for one yearin the United States