New Blood Test May Spot Early Colon Cancer

Study Shows Measuring Levels of CD24 Protein Can Detect Colon Cancer

By Charlene Laino
WebMD Health News

Reviewed By Louise Chang, MD

Jan 20, 2010 -- A new blood test has potential for detecting -- and even preventing
-- colon cancer, a study shows.

The test spots a protein called CD24 that is elevated in the presence of both colon cancer and growths that are destined to become colon cancer. In contrast, levels of the protein are low in healthy tissue.

CD24 is produced early in colorectal cancer development and may be involved in the spread of tumor cells, says researcher Sarah Kraus, PhD, of the Tel Aviv Souraski Medical Center in Israel.

"Colon cancer is often diagnosed at a late stage, when it has a poor prognosis. The idea of the new test is to detect the cancer earlier when it is more curable," she tells WebMD.

The test may also prove useful for identifying patients who would benefit most from colonoscopy, Kraus says.

The findings were released today in advance of the annual Gastrointestinal Cancers Symposium, being held later this week in Orlando, Fla.

Colorectal cancer is one of the most common forms of cancer, diagnosed in more than 150,000 people each year in the U.S. Although colonoscopy can detect the disease at an early stage when it is most curable -- and even prevent it by finding polyps before they become cancerous -- many people shun the procedure because of discomfort, pain, and a small risk of complications.

There are other noninvasive tests for colorectal cancer, such as the fecal occult blood test, which looks for blood in the stool. But occult, or hidden, blood is also found in the stool of people with a host of other conditions, such as hemorrhoids, resulting in a high rate of false-positive results.

CD24 not only predicts the presence of the cancer with a low false-positive and false-negative rate, but also can detect high-risk precancerous growths, Kraus says.

Removing them can prevent colon cancer from developing, she explains.

Testing for Colon Cancer

In the new study, Kraus and colleagues first measured levels of the CD24 protein in 63 people with colon cancer, 19 people with adenomas, or precancerous colon growths, and 68 healthy people.

"CD24 was [dramatically] elevated in colon cancer and adenoma patients, compared with healthy subjects," Kraus says.

Then, they further tested the accuracy of the CD24 blood test in 73 people: 11 had colon cancer, 24 had adenomas, and 38 showed no signs of colon cancer.

The researchers found that the test accurately detected colorectal cancer in 92% of cases; only 8% of colon cancers were missed. It gave false-positive results to 8% of people who didn't have the cancer.

As for adenomas, the test accurately caught 84% of growths. The false-positive rate was 11%.

The next step is to validate the findings in studies of larger groups of people, Kraus says.

The test is expected to cost less than $50, she says.

This isn't the first time researchers have reported they're a step closer to developing a blood test for colon cancer. Just last year, two teams of European investigators said they had developed tests that look for genetic fingerprints of tumor growth and spread in the blood, for example.

Which tests will eventually make it out of the lab and into the clinic is still anyone's guess, doctors concede.

"People are putting a lot of thought into developing blood tests that are highly accurate and can detect colon cancer at an early stage," says Robert P. Sticca, MD, of the University of North Dakota School of Medicine and Health Sciences and moderator of a news briefing.

"The research is very preliminary, but [if it pans out], it will be a very useful tool given how common colon cancer is," he tells WebMD.

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SOURCES: Press Program, Gastrointestinal Cancers Symposium.

Sarah Kraus, PhD, Tel Aviv Souraski Medical Center, Israel.

Robert P. Sticca, MD, University of North Dakota School of Medicine.

American Cancer Society web site.

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