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New Colon Cancer Test Shows Promise

WebMD Health News
Reviewed by Gary D. Vogin, MD

Jan. 30, 2002 -- Perfecting a simple, accurate, and noninvasive diagnostic test has been the elusive Holy Grail of colorectal cancer research. The best existing tests are highly invasive and widely perceived as uncomfortable or painful. As a result, many people who should be tested for colon cancer are not, and thousands of people die needlessly each year from the disease.

Now, researchers from Baltimore's Johns Hopkins University say they have developed a safe and reliable noninvasive test that can detect early colon cancers and precancerous polyps. The test involves the identification of a specific genetic marker in stool samples and may be clinically available within three years. Though it is not designed to replace invasive tests like colonoscopy or sigmoidoscopy, it could prove to be a valuable new screening tool.

"From a patient's point of view, this test is even simpler than a fecal occult blood test, because they only need to collect one sample instead of three," lead researcher Bert Vogelstein, MD, tells WebMD. "We hope this will be a good option for people at average risk who elect to have a noninvasive test, rather than an invasive one like colonoscopy or sigmoidoscopy."

The findings are the culmination of a decade of work by Vogelstein and Johns Hopkins colleagues. In the early 1990s, the researchers identified the adenomatous polyposis coli (APC) gene, and mutations in the gene were shown to be associated with molecular and cellular errors leading to tumor formation. The researchers have since developed a way to reliably detect the tumor marker in fecal DNA.

In the current study, published Jan. 31 in TheNew England Journal of Medicine, stool samples were analyzed from 28 people with early colon cancers, 18 people with premalignant polyps, and 28 people without disease. The test detected the genetic mutation in 61% of those with cancer, half of those with polyps, and none of the cancer-free controls.

The genetic marker test is not as reliable as colonoscopy -- the gold standard of colorectal cancer screening that has a sensitivity of 90%. The sensitivity of the APC test is comparable to sigmoidoscopy, Vogelstein says.

"The existing tests are good, but there is plenty of room for new tests that people would be more comfortable with," he says. "Right now, half a million people a year die of colon cancer worldwide. Most of those deaths could be prevented and much of that sickness spared if those tumors were found early."

Roughly 135,000 new cases of colorectal cancer are diagnosed in the United States each year, and there are 60,000 deaths from the disease. Routine screening is recommended for everyone 50 and older, but fewer than half of those eligible are screened.

The CDC's Cancer Prevention and Control center estimates that colorectal cancer deaths would drop by a third if everyone at moderate to high risk for the disease were tested. Moderate risk includes anyone who is 50 or older. You are at high risk if you have a close relative who has had colorectal polyps or colorectal cancer, or if you have inflammatory bowel disease.

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