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Computer model helps identify a genetic cause in colon cancer patients

By Sharon Gray

A new research paper concludes that a model called “MMRpredict” shows the best discriminating ability of four models evaluated to help identify colorectal cancer patients who should be screened for Lynch syndrome, an inherited cancer condition that accounts for about three per cent of all colorectal cancers. Its use could substantially reduce the proportion of colorectal cancer patients who are unnecessarily referred for genetic testing.

In a paper published Feb. 24 in the Journal of The National Cancer Institute, Dr. Roger Green and colleagues Drs. Patrick Parfrey, Michael Woods and Ban Younghusband of Memorial University’s Faculty of Medicine, discuss the results of a study on the ability of four models to distinguish between individuals who did and did not carry the inherited mutations responsible for Lynch syndrome. Mutations in genes that repair DNA are the cause of Lynch syndrome.

“It is important to identify mutation carriers because their treatment will be different and because members of their extended families must also be screened,” said Dr. Green. “However, the models to help identify Lynch syndrome patients were designed for use in high-risk patient populations and their value in the general patient population was unknown.”

The study carried out by Dr. Green and his colleagues examined a series of 725 colorectal cancer patients whose mutation status they had previously determined. By analyzing such factors as the age of the patient, the type of cancer, and the number of affected relatives, the model “MMRpredict” was the best of the four in predicting which patients carried a Lynch syndrome mutation.

“With the current criteria 50 per cent of all colon cancer patients would be candidates for molecular testing – but at this time testing is done only on a research basis,” explained Dr. Green. “If the MMRpredict model were used in the clinic, it would reduce this to 11 per cent, which is a more feasible number to test as part of clinical services.”

For colorectal cancer patients 75 years at diagnosis, MMRpredict appears to be an excellent screening tool that identifies an at-risk group that should undergo further diagnostic workup, he added.