HealthDay News — Fewer than half of younger adults with colorectal cancer (CRC) undergo mismatch repair (MMR) deficiency of DNA testing, according to a study published online in JAMA Oncology.

Talha Shaikh, MD, from Fox Chase Cancer Center in Philadelphia, and colleagues examined use of MMR deficiency testing in adults with CRC. They used data from the National Cancer Database to identify adult (<30 to ≥70 years) and younger adult (>30 to 49 years) patients with invasive colorectal adenocarcinoma diagnosed between 2010 and 2012 who had known MMR deficiency status. Data were included for 152,993 adults with CRC, of whom 43,143 underwent MMR deficiency testing.

The researchers found that 43.1% of the 17,218 younger adults underwent MMR deficiency testing, with an increase in the proportion from 2010 to 2012 (36.1% to 48%).

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Higher education level, later diagnosis year, early-stage disease, and number of regional lymph nodes examined (≥12) were independently associated with MMR deficiency testing regardless of age (odds ratios, 1.38, 1.81, 1.24, and 1.44). Associations were found for older age, Medicare, Medicaid, and uninsured status (odds ratios, 0.31, 0.89, 0.83, and 0.78) and for nonacademic versus academic/research facility type, rectosigmoid or rectal tumor location, unknown grade, and nonreceipt of definitive surgery (odds ratios, 0.44, 0.76, 0.61, and 0.33, respectively) with underuse of MMR testing.

“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 authors write.

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Shaikh T, Handorf EA, Meyer JE, et al. Mismatch repair deficiency testing in patients with colorectal cancer and nonadherence to testing guidelines in young adults [published online November 9, 2017]. JAMA Oncol. doi: 10.1001/jamaoncol.2017.3580