Blood Test May Predict Colon Cancer Risk
Excerpt By Merritt McKinney, Reuters Health

NEW YORK (Reuters Health) - A simple blood test that looks for a certain genetic alteration may identify people at risk of colorectal cancer, preliminary research released Thursday suggests.

The blood test, still in the experimental stages, does not detect colorectal cancer, but it may identify people who are likely to develop the disease and who would benefit from additional screening, the study's lead author told Reuters Health.

"This is preliminary and needs to be confirmed by more research," said Dr. Andrew P. Feinberg. "But we hope that it will be possible to identify patients in the general population at risk of cancer before they develop cancer."

In an interview, Feinberg, who is at Johns Hopkins University Medical School in Baltimore, Maryland, noted that "we have made much progress" in identifying people who are at risk of cardiovascular disease, such as those with high cholesterol. These people can be treated early, even before disease develops.

"We hope eventually to do the same kind of thing for cancer," he said.

The new blood test may identify people who should undergo more frequent screening for colorectal cancer, according to Feinberg. On the other hand, he said, people who have a low risk may be able to be screened less often.

But the researcher emphasized that "there is a lot of work that needs to be done" to show that a person who tests positive on the blood test is more likely to develop cancer in the future.

He noted that the present study looked at the risk of past or present cancer, but not the risk of cancer in the future.

And for the blood test to become practical, Feinberg said that it needs to be refined and made easier and cheaper to perform.

The test looks for "loss of imprinting" in the gene for a protein called insulin-like growth factor II (IGF2). Imprinting marks on DNA tell whether a gene came from the mother or the father.

Previous research has shown that loss of imprinting in the IGF2 gene occurs in about 30% of people with colorectal cancer, compared with only 10% of people without the disease.

To see whether the loss of imprinting in this gene could be used to identify people at risk of colorectal cancer, Feinberg used a DNA-based blood test to look for the alteration in 172 people who were undergoing the cancer screen colonoscopy.

Loss of imprinting was much more common in people with a family history of colon cancer and those who had the disease themselves, Feinberg's team reports in the March 14th issue of the journal Science.

People with a family history of the disease were about five times more likely to have lost imprinting in the IGF2 gene. And people with a history of growths called adenomas, which can become cancerous, were more than three times more likely to have loss of imprinting than people with no history of the growths.

Loss of imprinting was almost 22 times more common in people who had colorectal cancer or who'd had it in the past than in those with no personal history of the disease.

The study is "a step toward the goal of developing a noninvasive test for detecting cancer," according to Dr. David F. Ransohoff of the University of North Carolina at Chapel Hill.

In a related editorial, he, too, points out that the test does not look for cancer itself, but a person's "tendency" to develop cancer.

If this test is sensitive enough, however, Ransohoff adds, it may be useful in identifying people who can forego conventional cancer screening because they have a low lifetime risk of colorectal cancer.

Feinberg and a co-author are entitled to a percentage of any royalties that Johns Hopkins may receive through the sale of the technology used in the study. In addition, Feinberg is a paid consultant to the German biotech company Epigenomics AG, which has a licensing arrangement with the university.

SOURCE: Science 2003;299:1753-1755.

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