Although it is recommended for all colorectal cancer patients, most are not being screened for a common genetic syndrome that increases the risk of several forms of cancer and can influence treatment outcomes, according to a new study in JAMA Oncology.

In the largest U.S. study of its kind, researchers at Fox Chase Cancer Center studied compliance with DNA mismatch repair (MMR) deficiency testing with a focus on younger patients, and with a goal of understanding why so many are not screened despite the recommendation.

The researchers found that only 28 percent of adult colorectal cancer patients undergoing colorectal cancer resection were reported to have MMR deficiency testing performed on their tumours, including 43 percent of those ages 18-49.

Testing is especially important for younger patients, because that group has an increased incidence of Lynch syndrome.

MMR deficiency or its absence can impact treatment decisions and outcomes for colorectal cancer patients, and individuals and their family members who have this mutation may be at risk for additional malignancies.

Colorectal cancer is the second leading cause of cancer-related death in men, and the third-leading cause of cancer-related death in women.

“MMR deficiency is a characteristic feature of Lynch syndrome, and while Lynch syndrome causes only ~2-3% of colorectal cancers, MMR deficiency and is estimated to affect as many as 15 percent of colorectal cancer patients,” said Michael Hall, MD, associate professor, Department of Clinical Genetics at Fox Chase and an author of the paper. “MMR deficiency status is a marker of good prognosis and can help us guide treatment recommendations.”

The National Comprehensive Cancer Network updated its guidelines in 2014 to recommend screening for all colorectal cancer patients; previously the guidelines recommended screening only those patients whose family history suggested increased risk for MMR deficiency.

“This test tells physicians whether they must develop a prevention and early detection plan to reduce a patient’s risk for subsequent cancers associated with Lynch Syndrome,” said Nestor F. Esnaola, MD, MPH, associate director of Cancer Health Disparities and Community Engagement and professor of surgical oncology at Fox Chase. “Furthermore MMR deficiency testing helps identify patients who may not benefit from certain types of chemotherapy, but may experience a benefit from immunotherapy.”

The authors said that non-compliance with the screening guideline is a pervasive problem.

Their research identifies groups least likely to be screened and factors that contribute to underuse of the test, which may be valuable in planning interventions to encourage wider use.

Source: Fox Chase Cancer Center