Methylated DNA Blood Test Detects Colon Cancer

A new test uses free-floating DNA gleaned from blood for the early detection of colorectal cancer.

The presence of the methylated form of DNA encoding the so-called Septin 9 gene is found in the plasma of up to 57% of patients with all stages of colorectal cancer at high levels of specificity (95%), according to data presented at the annual meeting of the American Association for Cancer Research in Washington (DC, USA) in April 2006.

The data were gathered by scientists at Epigenomics AG (Frankfurt, Germany), a molecular diagnostics company developing tests based on DNA methylation. "The presence of methlated Septin 9 DNA in blood is a marker suited as an excellent population screening tool to identify a large number of asymptomatic cancers,” said Catherine Lofton-Day, Ph.D., vice president, molecular biology, at Epigenomics. "A blood-based screening assay will be more patient-friendly than the conventional colorectal cancer screening tool, which requires patients to collect and submit fecal samples for fecal occult blood testing--a considerable obstacle to patient compliance.”

The data came from two independent studies that determined Septin 9 levels in a total of 1,500 patients in three distinct categories. One group was known to be free from colon cancer after a colonoscopy. A second group included people with noncolorectal cancers and other noncancerous conditions, and a third group consisted of patients with a confirmed diagnosis of colorectal cancer. In an initial study of 501 samples, 57% of the colorectal cancers were detected. After validating the Septin 9 assay among the three known-status groups in a set of several hundred samples, Dr. Lofton-Day and colleagues predicted the diagnosis of colorectal cancer in an independent set of 790 patients. In this study the detection rate for all colorectal cancers was 50% (104 detected in 209 cases). The false-positive rate for both studies was 4-6%.

"Different stages of colorectal cancers were detected with similar sensitivity, and detection was not affected by location of the tumor in the colon,” explained Dr. Lofton-Day. "This is a reliable, noninvasive method to detect many patients with colorectal cancer who show little or no symptoms.”

The test to identify methylated Septin 9 DNA in blood is not intended to replace periodic colonoscopy or sigmoidoscopy screening but for use as part of routine yearly check-ups. Epigenomics has validated a panel of DNA methylation markers for incorporation into a colorectal cancer screening test in three large clinical studies involving about 2,000 patient samples. The first marker from the panel has been exclusively licensed to Roche Diagnostics (Basel, Switzerland).



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