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New Method for Early Detection of Colon Cancer

Genetic variations allow noninvasive test (September 4)

A new method to detect genetic variations that initiate colon cancer could be readily used for noninvasive colon cancer screening, according to a new study published in Cancer Prevention Research, a journal of the American Association for Cancer Research (AACR).

About 60% and 40% of patients with colorectal cancer have genetic variations in the genes APC and KRAS, respectively. Because these variations are also present in precancers, methods for spotting them can help detect colon cancers early. The new method described in the study can detect a single cancer-specific gene variation among 10,000 times the amount of normal DNA, and is up to 5,000-fold more sensitive than other noninvasive screening methods.

Bettina Scholtka, PhD, and colleagues used 80 human colon-tissue samples representing cancers and precancers to detect genetic variations using a combination of two techniques. First, locked nucleic acid (LNA)-based, wild-type blocking (WTB) polymerase chain reaction suppressed the normal DNA present in large quantities in the sample. Next, high-resolution melting (HRM) enhanced the detection of genetic variations.

The researchers were able to detect APC variations in 41 of the 80 samples. They were also able to detect previously unknown variations in APC. In contrast, the routinely used technique (direct sequencing) could detect variations in only 28 samples.

The researchers then analyzed 22 stool samples from patients whose colon tissues had APC variations, and nine stool samples from patients whose colon tissues did not have APC variations (controls). The researchers were able to detect APC variations in 21 out of 22 samples.

“By using our technique for examining a selection of genes that become mutated during the process of colon cancer formation, it is possible to detect the very first stage of colon cancer and even precancers in a stool sample,” said Scholtka. “It will be possible to prevent cancer in many cases by removing the precancerous lesions after early detection.”

Source: AACR; September 4, 2013.

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