A blood test may one day be used to determine a person's risk for colon cancer and could replace some of the invasive techniques currently used to screen for the disease, researchers say.
In a study appearing Friday in the journal Science, researchers at Johns Hopkins University Medical Center say that a molecular change that switches on a usually inactive gene signals a patient's increased risk of developing colon cancer and can be detected with a blood test.
"Up to now, there have been no tests for common cancer risks," said Dr. Andrew P. Feinberg, senior author of the study. "There are for other diseases, but not for cancer. Ultimately, that's what we hope this test will do."
Colon cancer is the third most deadly cancer in America. Each year about 148,000 new cases are diagnosed and about 56,000 people die from the disease. It is considered one of the most curable of the serious cancers because its early stages can be detected with a colonoscopy. But studies have shown that many patients dread and avoid the test, which involves drinking several quarts of a solution to clean the colon, followed by being deeply probed with a medical instrument.
A blood test that accurately defines a patient's colon cancer risk could reduce the need for such invasive procedures, experts say.
In the Hopkins study, Feinberg and his team analyzed blood samples from 172 patients who had had colonoscopies. The researchers were searching for chemical evidence of a process called "loss of imprinting," or LOI, in the insulin-like growth factor, or IGF2, gene from the patient's mother.
The Hopkins team found that those with a family history of colon cancer were five times more likely to have the LOI marker. Patients who had polyps, an early stage of cancer development, were three times more likely to have LOI, while patients with a personal history of colon cancer were 22 times more likely to have LOI. Among healthy patients with no family history of cancer, about one in 10 had the LOI marker.
Feinberg said that to prove LOI is a valid marker for colon cancer, the researchers will have to look at blood samples from many more randomly selected patients and follow them for several years. He said it may be five years before the test would be ready for general use.
"If the test proves out, then it could be used in the same way that lipid (cholesterol) testing is done now to evaluate heart disease risk," said Feinberg. He said people found to be at higher risk of colon cancer could then have further testing and close follow-up, while those with no indication of risk would need less monitoring.
Dr. Paul J. Limburg, director of the colorectal cancer center at the Mayo Clinic, said the Feinberg study "has the potential to be an important advance" in the detection of colon cancers.
"It would be very desirable to have a simple way to test patients through their blood to predict their risk of cancer in the colon and in organs as well," said Limburg. "Markers like this one may allow us to do that."
The study was funded by the National Cancer Institute, and the technology being developed is licensed by Hopkins to a firm called Epigenomics AG. Feinberg and some members of his team are entitled to a share of any royalties developed from the technology.
By Paul Recer
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