| [ Summary ] |
In the new guidelines for colorectal cancer screening edited by the U.S. Multisociety Task Force on Colorectal Cancer, stool DNA testing is referred to as one of the emerging technologies for screening for colorectal cancer. The rationale of this screening strategy comes from the evidence that diverse arrays of molecular alterations are involved in multi-step colorectal tumorigenesis, and that higher fecal DNA derived from exfoliated colonocytes yields from patients with colorectal cancer than from persons with no disease. According to the U.S. Guideline, subjects for stool DNA testing should be asymptomatic, average-risk individuals 50 years of age or older who are also subjects of conventional screening strategies, but not those in high risk categories such as hereditary cancer syndromes. During the ten year period starting in 1990, early detection of K-ras oncogenes in clinical samples by highly sensitive PCR-based methods represented the paradigm of single gene testing for colorectal cancer in stool samples. In the recent years, somatic DNA testing has included tests for multiple mutations in a set of genes known to alter in association with colorectal cancer, because of the concept that no single mutation has been identified that is expressed across all colorectal tumors. The sensitivity for detecting cancer is higher (about 60%) with DNA testing for multiple genes than that for single genes, while specificity is similarly high (90-100%) in both types of testing. In the future, stool DNA testing may hold promise for colorectal cancer screening as a non-invasive method, together with developing imaging technologies, including virtual colonoscopy and FDG-PET. |