Up to 15% 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 MD Anderson uncovered new data about dMMR’s hereditary basis in rectal cancer which may guide physicians in diagnoses, treatment and preventive measures, and in exploring potential new therapy options. Results from the study were reported in the July 18 online issue of the Journal of Clinical Oncology.
The study provided a benchmark for current treatment approaches including chemotherapy and surgery and confirmed dMMR patients likely are to have a good prognosis. It 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 tailored to specific characteristics, such as a person’s genetic makeup, or the genetic profile of an individual’s tumor.
“Our paper provides a perfect illustration of how the power of precision medicine can be realized,” said Y. Nancy You, M.D., associate professor of Surgical Oncology. “This new genetic understanding of dMMR provides immediate implications for telling patients how well they will do long term and for choosing the best surgical and chemotherapy options.”
Read more about this study in MD Anderson's newsroom.