Mismatch Repair–Deficiency Testing in Patients With Colorectal Cancer

Key Points

  • MMR deficiency testing was performed in 28% of all patients with colorectal cancer.
  • Testing was performed in 43% of younger patients.

In a study reported in JAMA Oncology, Shaikh et al found that despite existing recommendations, mismatch repair (MMR)-deficiency testing is underused in patients with colorectal cancer, including younger patients. As noted by the authors, MMR deficiency is observed in up to 15% of sporadic colorectal cancers and is characteristic of Lynch syndrome, which has a higher incidence in younger adults with colorectal cancer.

The study involved National Cancer Database data from 152, 993 adult patients (aged < 30 to ≤ 70 years), including 17,218 younger patents (aged < 30 to 49), with invasive colorectal adenocarcinoma diagnosed between 2010 and 2012 and a known MMR deficiency testing status.

MMR Deficiency Testing

Among all patients, 43,143 (28.2%) underwent MMR deficiency testing, with the proportion increasing from 22.3% to 33.1% between 2010 and 2012 (P < .001). Among the younger adult patients, 7,422 (43.1%) underwent testing, with the proportion increasing from 36.1% to 48.0% between 2010 and 2012 (P < .001).

Factors Associated With Testing

Irrespective of age, factors independently associated with an increased likelihood of testing were higher educational level (odds ratio [OR] = 1.38, 95% confidence interval [CI] = 1.15–1.66), later diagnosis year (OR = 1.81, 95% CI = 1.65–1.98), early-stage disease (OR = 1.24, 95% CI = 1.18–1.30), and number of regional lymph nodes examined (≥ 12; OR = 1.44, 95% CI = 1.34–1.55). Factors associated with a reduced likelihood were older age (OR = 0.31, 95% CI = 0.26–0.37), Medicare (OR = 0.89, 95% CI = 0.84–0.95), Medicaid (OR = 0.83, 95% CI = 0.73–0.93), uninsured status (OR = 0.78, 95% CI = 0.66–0.92), nonacademic vs academic/research facility type (OR = 0.44, 95% CI = 0.34–0.56), rectosigmoid or rectal tumor location (OR = 0.76, 95% CI = 0.68–0.86), unknown grade (OR = 0.61, 95% CI = 0.53–0.69), and no receipt of definitive surgery (OR = 0.33, 95% CI = 0.30–0.37).

The investigators concluded: “Despite [the] recent endorsement of universal use of MMR deficiency testing in patients with [colorectal cancer] and well-established guidelines aimed at high-risk populations, overall utilization of testing is poor and significant underuse of testing among young adults persists. Interventions tailored to groups at risk for nonadherence to guidelines may be warranted in the current era of universal testing.”

The study was supported by the National Cancer Institute.

Nestor F. Esnaola, MD, MPH, MBA, of Fox Chase Cancer Center, is the corresponding author of the JAMA Oncology article. 

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.




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