MMR/MSI Testing for CRC Climbs, But Variations Persist

TOPLINE:

Testing for mismatch repair (MMR) and microsatellite instability (MSI) among patients with colorectal cancer (CRC) increased from 22.7% in 2012 to 71.5% in 2021, but variations in access remain, with testing rates differing by cancer stage, individual hospital, patient sex, race, and insurance status.

METHODOLOGY:

• In 2017, the National Comprehensive Cancer Network (NCCN) recommended universal testing for MMR and MSI among patients with CRC, but studies suggest that testing may still be underused.
• To assess trends and factors associated with MMR/MSI testing in the United States, researchers evaluated 834,797 patients diagnosed with stage I to IV CRC between 2012 and 2021 across 1366 Commission on Cancer–accredited hospitals in the National Cancer Database.
• The variability in MMR/MSI testing was assessed in relation to both patient and hospital-level factors.
• Overall, 70.7% patients had colon cancer, 7.3% had rectosigmoid cancer, and 22.0% had rectal cancer. The median patient age was 66 years; just over half (53%) were men, 81.8% were White, and 11.9% were Black.

TAKEAWAY:

• Overall, 43.9% patients underwent MMR/MSI testing, but testing rates increased more than threefold between 2012 and 2021 — from 22.7% to 71.5%. Still, testing rates varied depending on a range of factors.
• About 22% variability in MMR/MSI testing was attributed to hospital-level variations, with the best vs worst performing hospitals reporting testing rates of 90% vs 2%. This hospital-level variation may be due to testing protocol differences at individual institutions, the authors said.
• The likelihood of undergoing MMR/MSI testing was lower in patients with stage IV vs stage I disease (adjusted odds ratio [aOR], 0.78) but higher in those with stage II (aOR, 1.53) and III (aOR, 1.40) disease.
• The likelihood of undergoing MMR/MSI testing was slightly lower for men than for women (aOR, 0.98) and for Black patients than for White patients (aOR, 0.97). Having a lower household income, public or no insurance (vs private insurance), or living a longer distance (more than 5 miles) from the treatment facility was also associated with lower odds of testing.

IN PRACTICE:

“This cohort study indicated that MMR/MSI testing increased markedly, suggesting increased NCCN guideline adherence,” the authors said. However, variations still exist by cancer stage, hospital, and patient factors. Implementing “widespread institution-level reflexive testing for every initial diagnostic biopsy” can improve testing rates and reduce disparities, the authors suggested.

SOURCE:

This study, led by Totadri Dhimal, MD, University of Rochester Medical Center, Rochester, New York, was published online in JAMA Oncology.

LIMITATIONS:

The study lacked clinical granularity, and potential coding inaccuracies and incomplete data could have affected the interpretation and generalizability of the findings.

DISCLOSURES:

No funding information was provided for the study. One author reported receiving author royalties from UpToDate outside the submitted work.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.