A blood test designed to enable simple screening for colon cancer has been hailed by experts as a major advance. The test detects cancer due to a chemical change called methylation that occurs disproportionately in two key genes in colorectal tumor cells.

Since more people should be willing to have a simple blood test, the screening method could help identify those patients who need a more invasive, more diagnostically rigorous colonoscopy.

The U.S. death toll from the condition is around 50,000 a year. The American Cancer Society recommends that men over the age of 50 have about one colonoscopy every 10 years, and that those at a higher risk be screened earlier and more often. Yet until now, only invasive colonoscopies and stool tests have been available and compliance by those deemed in need of screening is disappointingly low, at less than 50 percent. Screening programs have been shown to cut deaths by allowing more victims to receive earlier, curative treatment so a simpler test could save lives by encouraging more people to get screened.

The developers of the new test, OncoMethylome Sciences, based in Liège, Belgium, say their method, which relies on one three-milliliter sample of blood, has the potential to boost compliance rates and conserve precious health service resources.

The test identifies the presence of methylated SYNE1 and FOXE1 genes, which mark out colorectal cancer cells. The researchers compared test results from 686 healthy control patients with 193 patients already diagnosed with the disease. The test was able to detect colorectal cancer in 77 percent of those subjects with the disease, according to data presented at the Congress of the European Cancer Organization in Berlin, Germany, on Monday. It correctly identified healthy, noncancerous patients in 91 percent of cases.

"This test has potential to provide a better balance of performance, cost-effectiveness, and patient compliance than other options currently available for colorectal cancer screening," says Joost Louwagie, vice president of product development at OncoMethylome.

Louwagie hopes that with further testing and refinements the test will become more sensitive and provide fewer false-positive results. But he says that even a 77 percent sensitivity would be "very useful" if it were applied to the large numbers of people who decide not to have screening using more-intrusive methods. He stresses, however, that colonoscopies remain the gold standard for diagnosing the disease.

Ernst Kuipers, head of the colorectal screening program and a professor of medicine at Erasmus University Medical Center in Rotterdam, praises the results. "This is an excellent new method, technically very well done," he says. "It represents a major advance on what we have now."