AP MEDICAL WRITER

Brenda Coleman

CHICAGO (AP)—A blood test commonly used to detect new malignancies after surgery for colon cancer—the second leading U.S. cancer killer—is virtually worthless, researchers found in a large new study.

About 500,000 Americans now get the test at least once and possibly many times after colon-cancer surgery, researchers estimated in Wednesday’s issue of The Journal of the American Medical Association.

The $55 test, called CEA, for ‘‘carcinoembryonic antigen,’‘ measures blood levels of a carbohydrate-protein molecule that colon cancers may produce in large quantities, researchers said.

Though the test often warns that cancer has reappeared in the colon or elsewhere, it misses many recurrences. In other patients, it often suggests the presence of malignancies when none exist, the researchers found.

When the test result is right, it often is too late; and when it is wrong, far more expensive tests and even surgery are needed to rule out cancer, they found.

The researchers, led by Dr. Charles G. Moertel of the Mayo Clinic, studied 1,216 colon-cancer patients treated after surgery at cancer centers, universities and community clinics in a number of states.

In 84 percent, or 1,017, of the cases, doctors measured CEA levels to try to get an early warning for new cancers, researchers found in the eight-year study completed this year.

Exploratory surgery was performed on 115 patients with elevated CEA levels, and malignancies were surgically removed from 47 patients, the researchers said.

Yet only 2.3 percent of all CEA-monitored patients who had second operations were alive and cancer free a year later, compared with 2 percent of those who were not CEA monitored and had second operations.

‘‘The results of this study are singularly disappointing in meeting the bottom-line objective of CEA monitoring, that is, an increase in cure rate,’‘ the researchers said.

Not only that, but the cost for each possible cure totaled $500,000 or more, including all the followup tests and operations among CEA-monitored patients, the researchers calculated.

‘‘The article shows clearly that a common practice, at best, has very, very small effects,’‘ said Dr. Robert H. Fletcher, an adjunct professor of medicine at the University of Pennsylvania who did not participate in the study.

‘‘And that comes at a high cost both in human terms—all of the testing and retesting prescribed—and in dollars,’‘ he added by telephone Monday from Philadelphia, where he also co-edits the Annals of Internal Medicine.

Fletcher agreed with the study’s authors, who suggested the total costs of CEA monitoring aren’t worth the few extra cures.

In the past, it was hoped CEA monitoring might save one in five patients with recurring cancer and reduce the colon-cancer death rate 5 percent overall, Moertel and his team said.

Colon cancer will kill about 57,000 Americans this year, second to lung cancer, which will kill 149,000, the American Cancer Society estimates.