Blood-Based Methylation Assay Detects Colorectal Cancer

An on-going evaluation of a blood-based methylation assay for the screening and detection of colorectal cancer (CRC) has produced promising results.

The outcome of the evaluation was presented on September 21, 2009 at the 15th Congress of the European Cancer Organization and 34th Congress of the European Society for Medical Oncology in Berlin, Germany. Data on the method of methylation marker selection, the analytical performance of the test and the first results from a multi-center feasibility study was presented. The ultimate goal of the program was to provide a sensitive, specific, and patient-friendly option for colorectal cancer screening.

The blood-based methylation assay was developed by OncoMethylome (Liege, Belgium). Methylation is a natural control mechanism that regulates gene expression in DNA. Abnormal methylation of certain genes, such as tumor suppressor genes, can silence gene expression and is associated with cancer development. Genes, whose methylation is linked to cancer, are called methylation markers. OncoMethylome owns proprietary technology that is highly sensitive and capable of detecting methylation markers, and thereby cancer, even in early stages of cancer development.

"We optimized the methods of DNA extraction and methylation detection so that we could detect low levels of methylated genes in blood samples of people with colorectal cancer," says Dr. Louwagie, OncoMethylome's VP of product development, "and we were able to find a high frequency of two newly reported methylation genes, SYNE1 and FOXE1, in colorectal cancer patients. Equally important, the same methylation genes occurred infrequently in noncancerous individuals."

Once the test is validated, it will be a more acceptable alternative for those not wanting to undergo a colonoscopy or to do a fecal occult blood test (FOBT). More colorectal cancers will be discovered at an early stage of the disease.

Colorectal cancer (CRC) occurs in approximately one in every 17 people during their lifetime and is the second leading cause of cancer-related death in the United States and Europe, where a combined total of about 560,000 people develop the disease each year and 250,000 die from it. CRC typically occurs in adults (over age 50) but, because symptoms are often not present in early-stage disease, less than 40% of patients are diagnosed at an early stage when the disease is most treatable.

Colonoscopy, where the interior of the colon and rectum is examined using a tiny camera mounted on a flexible tube, is the most sensitive test currently available and has the benefit of allowing removal of precancerous polyps. Colonoscopy, however, is invasive, expensive, requires bowel preparation and skilled practitioners, thereby making it inaccessible or unacceptable for many patients.

Fecal occult blood testing (FOBT), where patients give stool samples to be analyzed, is less invasive than colonoscopies, inexpensive and is used in national screening programs in some European countries. This test detects the presence of blood in a stool sample, which can be due to CRC but also to other noncancerous conditions. Due to patients' reluctance to handle stool samples, compliance for even the best-organized national screening programs in Europe is often less than 50%. In the US, less than 20% of the targeted population undergoes FOBT screening within a two-year period.

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