MMR Deficiency Tests Underused in Young Adults With Colorectal Cancer

Utilization of testing for mismatch repair (MMR) deficiency was poor and underused in a large population of patients with colorectal cancer, according to the results of a study published in JAMA Oncology.

MMR deficiency is a characteristic of Lynch syndrome, which has an increased incidence in young adults diagnosed with colorectal cancer. In addition, confirmation of MMR deficiency can affect prognosis and response to chosen systemic therapy.

“Our study demonstrates that, despite growing interest in and endorsement of universal testing for MMR deficiency in patients with colorectal cancer during the study period, as well as longstanding, well-established guidelines aimed at high-risk populations, utilization of testing in this population was limited and significant underuse of testing among younger adults persisted,” wrote Talha Shaikh, MD, of Fox Chase Cancer Center in Philadelphia, and colleagues.

The study evaluated the use of MMR deficiency testing in adults with colorectal cancer from the National Cancer Database. The researchers looked at all adults aged < 30 to ≥ 70 years with a colorectal cancer diagnosis between 2010 and 2012. They identified 152,993 adults with a mean age of 66.9 years.

MMR deficiency testing was performed in only 28.2% of patients. The proportion of patients who underwent testing was higher in the 17,218 younger adult (< 30 to 49 years) patients (43.1%). The proportion of patients who underwent testing increased among the total population from 22.3% in 2010 to 33.1% in 2012 (P < .001), and among younger patients as well, from 36.1% in 2010 to 48.0% in 2012 (P < .001).

The researchers identified several characteristics associated with increased likelihood of MMR deficiency testing, including higher education level (odds ratio [OR], 1.38), later diagnosis year (OR, 1.81), early-stage disease (OR, 1.24), and number of regional lymph nodes examined (12 or greater; OR, 1.44).

In contrast, underuse of MMR deficiency testing was associated with older age (OR, 0.31); Medicare (OR, 0.89), Medicaid (OR, 0.83), or uninsured (OR, 0.78) status; nonacademic vs academic/research facility type (OR, 0.44); rectosigmoid or rectal tumor location (OR, 0.76); unknown grade (OR, 0.61); and nonreceipt of definitive surgery (OR, 0.33).

“Of particular concern, our study noted significant independent associations between patient socioeconomic and insurance status, as well as cancer program location and type and utilization of MMR deficiency testing, suggesting that patient and healthcare system–level interventions tailored to groups at risk for nonadherence are warranted to ensure optimal and uniform implementation of newly endorsed, universal testing guidelines,” the researchers wrote.

In an editorial published with the study, Stanley R. Hamilton, MD, of the University of Texas MD Anderson Cancer Center in Houston, called the study by Shaikh et al “sobering,” pointing out that in the years since the study (2012), “additional professional groups and organizations have recommended universal testing of colorectal cancer, including a recent clinical practice guideline developed in accordance with the Institute of Medicine (now National Academy of Medicine) process for unbiased guidelines.”

“Efforts must continue to meet the goal of universal testing and be accompanied by studies to evaluate the clinical utility of high-level microsatellite instability/deficient MMR testing in reducing mortality from colorectal cancer,” Hamilton wrote.