DNA test shows promise for identifying patients with colorectal cancer

Testing for DNA changes in stools might provide a new, accurate, and less invasive way to screen patients for colorectal cancer, conclude the authors of a research letter in this week’s issue of THE LANCET.

Colorectal cancer is one of the most common cancers in the industrialised world, and early detection might help to reduce the risk of death from the disease. However, although several methods of detection are available, these procedures are either uncomfortable for the patient or are not specific or sensitive enough to be suitable as screening tools.

Hannes M Müller from the Medical University Innsbruck, Austria, and colleagues investigated whether patients with colorectal cancer could be identified by testing stool samples for changes in DNA methylation-a form of genetic alteration that is common in colorectal cancer cells. The researchers used a polymerase chain reaction (PCR) assay to identify DNA changes in stools from patients with the disease and from healthy controls, to assess the most promising DNA methylation markers from a long list of candidate genes. They then tested for these potential markers in samples from two sets of patients and healthy controls, comprising a total of 49 individuals.

A gene known as SFRP2 was methylated more frequently in DNA from the stools of patients with colorectal cancer than in samples from people without the disease, with a sensitivity of 77-90% and specificity (a measure of reliability, relating to proportion of “false-positive” and “false-negative” results) of 77%. SFRP2 methylation could, therefore, be useful as a marker in screening for colorectal cancer.

Martin Widschwendter, the principle investigator of this study, comments: ”To our knowledge, SFRP2 methylation represents one of the most sensitive markers for identifying colorectal cancer, besides mutation analysis and protein analysis, in stool samples. Whether a panel of genetic and epigenetic markers in stool could be used to identify colorectal cancer at an early stage remains to be shown.”

Contact:
Dr Martin Widschwendter, Department of Obstetrics and Gynecology, Medical University Innsbruck, Anichstrasse 35, A-6020 Innsbruck, Austria. Fone: +43 512 504 81055; Fax: +43 512 504 23112; Email: martin.widschwendter@uibk.ac.at