DNA Test Detects Early Colon Cancer

A safe and reliable DNA stool test can detect the earliest, curable stages of colon cancer, according to scientists at the Kimmel Cancer Center at Johns Hopkins (Baltimore, MD, USA). Studies of the test were reported in the January 31, 2002, issue of the New England Journal of Medicine.

Mutations in the APC gene cause the molecular and cellular errors that result in colon cancer. To detect these, scientists had to develop a new way to reliably identify the mutated DNA in the stool of patients with early-stage colon cancer. What made this difficult was that there are thousands of possible mutations that can occur in the gene and finding just one can be very difficult. The scientists developed new technology called Digital Protein Truncation (Dig-PT), which allows extracted DNA to be divided into separate, smaller portions so that mutated copies stand out. Dig-PT was used to analyze all of the stool samples in the current study.

The investigators analyzed stool samples from 74 individuals, including 28 with early colon cancers, 18 with premalignant colon tumors, and 28 with no disease. The test detected a genetic mutation in 61% of those with early colon cancer, half of those with premalignant adenomas, and in none of those who were free of disease. The test holds promise as a screening test because it is painless, risk-free, and yields no false-positives.

"The advantage of using the APC gene as a biomarker is that, unlike tests for hidden blood or some previously used markers, it is exquisitely specific and found in the earliest and curable stages of tumor formation,” said Bert Bogelstein, M.D., professor of oncology at the Kimmel Cancer Center. "If this test identifies mutations of the APC gene, it means there is extremely likely to be a cancer or premalignant growth.




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