New Test May Better Identify Certain Colorectal Cancer Types

Some people with colorectal cancer have defects in their so-called DNA mismatch repair genes. Researchers test for these mutations by looking for a gene marker called microsatellite instability, which is caused by those gene defects. These mutations indicate that the cancer is likely an inherited condition called Lynch syndrome. It's important to identify patients with Lynch syndrome because they and their family members are at an increased risk of colorectal and other cancers. Patients with a non-hereditary form of colorectal cancer that shows microsatellite instability tend to have a better prognosis than other cancer patients, but they don't respond to a common cancer drug called 5-fluorouracil.

Rosa M . Xicola, a graduate student at the Germans Trias i Pujol Hospital in Barcelona, and colleagues tested two different methods, a standard method and an experimental method, of identifying patients with microsatellite instability. They found that the experimental method better identified--and more accurately ruled out--patients with defects in DNA mismatch repair genes. Furthermore, their results suggest that an even simpler test could be developed to identify patients with these mutations.

"The improved test could result in more patients being assigned to proper treatment based on their disease profile," the authors conclude.

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