Genetic cause of 15 percent of colorectal cancer diagnoses identified

From University of Texas M. D. Anderson Cancer Center:

IMAGE: This is Y. Nancy You, M.D. view more

Credit: MD Anderson Cancer Center

Up to 15 percent of colorectal cancers show a genetic mutation known as DNA mismatch repair deficiency, or dMMR. Until now, little has been known about how the mutation behaves in rectal cancer patients, what causes dMMR, and which treatments may be most effective.

A study at The University of Texas MD Anderson Cancer Center uncovered new data about dMMR’s hereditary basis in rectal cancer which may guide physicians in diagnoses, treatment and preventive measures, and in explorating of potential new therapy options. Results from the study, which examined 62 patient records from 1992 to 2012, were reported in the July 18 online issue of the Journal of Clinical Oncology.

The retrospective study provided a benchmark for current treatment approaches including chemotherapy and surgery and confirmed dMMR patients likely are to have a good prognosis. The study also highlighted the need to pay attention to long-term care after surviving rectal cancer.

DNA mismatch repair is the body’s method for repairing mutations or gene defects that occur during cell division. Sometimes things go awry with this vital tool, resulting in increased mutations and cancer. Four genes – MLH1, MSH2, MSH6 and PMS2 – previously have been associated with DNA mismatch repair. Until now, researchers believed MLH1 and MSH2 were the main culprits causing the DNA repair machinery to break down. The MD Anderson study found MSH2 and MSH6 to be most commonly found among dMMR rectal cancer patients.

The paper’s author believes such genetic information allows for a more tailored approach to diagnosis and treatment known as precision medicine, which is the focus of President Obama’s Precision Medicine Initiative that launched in 2015. Precision medicine encourages therapeutic options …

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