Nonadherence to Mismatch Repair Deficiency Testing High in Patients With Colorectal Cancer

11/16/17

Testing for mismatch repair deficiency remains underused among adults with colorectal cancer (CRC), despite the existence of well-established guidelines aimed at high-risk populations, according to a recent study.

Mismatch repair deficiency of DNA occurs in up to 15% of cases of sporadic CRC and is an important sign of Lynch syndrome, which occurs more frequently in adults younger than 50 years with CRC.

Talha Shaikh, MD, radiation oncologist, Fox Chase Cancer Center (Phildelphia, PA) and colleagues assessed 152,993 adults with invasive colorectal adenocarcinoma diagnosed between 2010 and 2012 and known mismatch repair deficiency. Mean patient age was 66.9 years, and 51.4% of patients were men.

Patients were classified as adults (younger than 30 years to at least 70 years) or young adults (younger than 30 years to 49 years). Patient data was obtained from the National Cancer Database. The researchers defined the primary outcome as receiving testing for mismatch repair deficiency. Independent predictors of testing in adult and/or young adult patients were identified through multivariable logistic regression.

Results of the study were published in JAMA Oncology (online November 9, 2017; doi:10.1001/jamaoncol.2017.3580).

Among the total patient population, only 43,143 (28.2%) received testing for mismatch repair deficiency. Results showed that the proportion of patients who received testing had increased between 2010 (22.3%) and 2012 (33.1%). However, only 7422 (43.1%) young adult patients with CRC received testing, with this proportion increasing between 2010 (36.1%) and 2012 (48.0%).

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The researchers found that higher education level, later year of diagnosis, early stage disease, and the number of regional lymph nodes examined (at least 12) were independently associated with receiving MMR deficiency testing, regardless of age. However, factors including older age, Medicare, Medicaid or uninsured status, nonacademic vs academic/research facility type, rectosigmoid or rectal tumor location, unknown grade, and not receiving definitive surgery were associated with the underuse of testing.

“Despite recent endorsement of universal use of [mismatch repair] deficiency testing in patients with CRC and well-established guidelines aimed at high-risk populations, overall utilization of testing is poor and significant underuse of testing among young adults persists,” the researchers concluded. “Interventions tailored to groups at risk for nonadherence to guidelines may be warranted in the current era of universal testing.”—Christina Vogt