Blood Test Detects Colon Cancer

Jan. 24, 2008 (Orlando) -- A novel blood test holds promise for both detecting and preventing colon cancer, researchers report.

The test spots a protein called colon cancer-specific antigen-2 (CCSA-2) that is elevated in the presence of colon cancer or growths that are destined to become colon cancer. In contrast, the protein appears to be rare in low-risk colon polyps and healthy tissue.

"Right now, we really don't have a simple, accurate, and noninvasive method for detecting colon cancer. CCSA-2 is a blood protein that predicts the presence of the cancer with a low false-positive and false-negative rate," says Nicholas J. Petrelli, MD, of the Helen F. Graham Cancer Center in Wilmington, Del.

"Just as importantly," Petrelli tells WebMD, the test detects "high-risk premalignant polyps which, if left alone, will directly lead to cancer. If we remove them, we can prevent colon cancer from developing."

Petrelli moderated a news briefing to discuss the findings, which are being presented at the annual Gastrointestinal Cancers Symposium (GCS) this weekend in Orlando.

CCSA-2 Test Unique

Colorectal cancer is one of the most common forms of cancer, diagnosed in more than 150,000 people each year in the United States. 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 avoid 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 false-positive results in up to 90% of cases.

The same research team reported earlier last year that two of CCSA-2's cousins, known as CCSA-3 and CCSA-4, can also indicate the presence of colorectal cancer.

The CCSA-2 test is unique in that it can distinguish between people who have advanced, high-risk adenomas (growths almost certain to become colon cancers) and non-advanced, low-risk adenomas or polyps that almost certainly will not lead to cancer, says researcher Eddy S. Leman, PhD, an instructor in the department of urology at Johns Hopkins Hospital in Baltimore.

"The higher the level of CCSA-2 in the blood, the greater the chance of having colorectal cancer or a high-risk adenoma," he tells WebMD.