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MMR deficiency testing remains low in colorectal cancer patients

 

Key clinical point: Utilization of mismatch repair (MMR) deficiency testing is poor among patients with colorectal cancer, and remains particularly low among young adults despite national guidelines calling for universal testing.

Major finding: Only 28% of patients overall, and only 43% of younger patients, underwent MMR deficiency testing.

Data source: 152,993 cases from the National Cancer Database.

Disclosures: This study was funded by a grant from the National Institutes of Health, National Cancer Institute. The authors reported having no conflicts of interest.

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Study highlights “sobering” lack of testing

 

The findings by Shaikh et al. are sobering, given the overwhelming published evidence regarding the importance of MMR deficiency testing, and they underscore a need to determine the causes of the low testing rates, according to Stanley R. Hamilton, MD.

Importantly, they also highlight areas that are “potentially actionable.” For example, the higher frequency of testing among those with higher educational levels, and underuse of testing in older patients and those from nonacademic facilities suggest that better education of physicians and patients about the value of testing could improve adherence to guidelines, Dr. Hamilton wrote in an editorial (JAMA Oncol. 2017 Nov 9. doi: 10.1001/jamaoncol.2017.3574).

Further, the lower frequency of testing among certain demographic groups suggests a need to address underserved and underresourced patient populations, he said, concluding that efforts must continue to meet the goal of universal testing and that those efforts must be accompanied by studies to evaluate the clinical utility of testing in reducing CRC mortality.
 

Dr. Hamilton is with the University of Texas MD Anderson Cancer Center, Houston. He is a member of the Fred Hutchinson Cancer Research Scientific Advisory Committee, a consultant for LOXO Oncology, and a member of the HalioDx Scientific Advisory Committee. He has a financial relationship with The Johns Hopkins University School of Medicine and with Merck.


 

FROM JAMA ONCOLOGY

 

Overall utilization of mismatch repair (MMR) deficiency testing is poor among patients with colorectal cancer, and utilization also remains low among young adults despite national guidelines calling for universal testing, according to an analysis of cases from the National Cancer Database.

The findings suggest that interventions that target groups at risk for nonadherence to guidelines may be warranted, wrote Talha Shaikh, MD, and colleagues at Fox Chase Cancer Center, Philadelphia. The report was published in JAMA Oncology (2017 Nov 9. doi: 10.1001/jamaoncol.2017.3580).

Of 152,993 adults with colorectal cancer (CRC) who were included in the study, only 28% underwent MMR deficiency testing, and of 17,218 aged 30-49 years, only 43% were tested. The proportion of patients tested in both groups increased between 2010 and 2012 (from about 22% to 33%, and from about 36% to 48%, respectively).

After the researchers controlled for all other covariates, factors significantly associated with being tested were higher educational level (odds ratio, 1.38), later diagnosis year (OR, 1.81), early-stage disease (OR, 1.24), and number of regional lymph nodes examined (OR, 1.44 for 12 or more lymph nodes). Factors associated with underuse of testing were older age (OR, 0.31), insurance status (Medicare, Medicaid, uninsured; ORs, 0.89, 0.83, and 0.78, respectively), research facility type (nonacademic vs. academic; OR, 0.44), rectosigmoid or rectal tumor location (OR, 0.76), unknown grade (OR, 0.61), and nonreceipt of definitive surgery (OR, 0.33).

MMR deficiency occurs in up to 15% of sporadic CRC and is a feature of Lynch syndrome, which occurs most often in patients under age 50 years. National guidelines have long recommended routine MMR deficiency testing for CRC patients in that age group, and universal testing has been recommended since 2014.

“Although the proportions of patients tested increased during the study period, our results suggest that underutilization of MMR deficiency testing was significant and pervasive, even among young patients with CRC with a well-established risk of Lynch syndrome. Our study ... identifies significant groups at risk for potential nonadherence to newly implemented universal testing guidelines moving forward,” the investigators said, noting that the associations between type and utilization of patient testing and socioeconomic status, insurance status, and cancer program location are of particular concern.

Ongoing analyses to track progress toward “closing this important clinical service gap,” will be needed, they concluded.

This study was funded by a grant from the National Institutes of Health, National Cancer Institute. The authors reported having no conflicts of interest.

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