Mismatch repair (MMR) and microsatellite instability (MSI) testing has increased among patients with colorectal cancer (CRC) from 22.7 percent in 2012 to 71.5 percent in 2021. However, there are still access issues, with testing rates varying depending on the stage of the cancer, the individual hospital, the patient’s sex, race, and insurance status.
METHODOLOGY:
Although studies indicate that testing may still be underused, the National Comprehensive Cancer Network (NCCN) recommended universal MMR and MSI testing for CRC patients in 2017.
Researchers looked at 834,797 patients who were diagnosed with stage I to IV CRC between 2012 and 2021 at 1366 Commission on Cancer–accredited hospitals in the National Cancer Database in order to evaluate trends and factors associated with MMR/MSI testing in the United States.
Both patient-level and hospital-level factors were taken into consideration when evaluating the variation in MMR/MSI testing.
7.3% of patients had rectosigmoid cancer, 22.0 percent had rectal cancer, and 70.7% of patients had colon cancer. The average age of the patients was 66; 53 percent were men, 81.8% were White, and 11.9% were Black, making up just over half.
TAKEAWAY:
Although testing rates increased more than threefold between 2012 and 2021, from 22.7% to 71.5 percent, 43.9% of patients underwent MMR/MSI testing. Still, a variety of factors affected testing rates.
Hospital-level variations were responsible for approximately 22% of the variation in MMR/MSI testing, with the best and worst performing hospitals reporting testing rates of 90% and 2%, respectively. According to the authors, there may be differences in testing protocols between institutions that account for this variation at the hospital level.
Patients with stage IV disease were less likely to undergo MMR/MSI testing than those with stage I disease (adjusted odds ratio [aOR], 0.78), but those with stage II disease (aOR, 1.53) and stage III disease (aOR, 1.40) were more likely to do so.
Men were slightly less likely than women to undergo MMR/MSI testing (aOR, 0.98), and Black patients were less likely than White patients to do so (aOR, 0.97). A lower likelihood of testing was also associated with living a longer distance (more than 5 miles) from the treatment facility, having public or no insurance (as opposed to private insurance), or having a lower household income.
IN PROCESS:
According to the authors, “This cohort study indicated that MMR/MSI testing increased significantly, suggesting increased NCCN guideline adherence.” However, there are still variations based on the cancer stage, the hospital, and the patient. The authors suggested that “widespread institution-level reflexive testing for every initial diagnostic biopsy” could reduce disparities and increase testing rates.
SOURCE:
The online version of this study was published in JAMA Oncology by Totadri Dhimal, MD, of the University of Rochester Medical Center in Rochester, New York.
LIMITATIONS:
The study lacked clinical granularity, and the findings’ interpretation and generalizability may have been impacted by possible coding errors and incomplete data.
DISCLOSURES:
The study did not have any information regarding its funding. Outside of the submitted work, one author reported receiving author royalties from UpToDate.
As part of the process, several editorial tools, including AI, were used to create this article. Before being published, this content was reviewed by human editors.
