Oct. 31, 2023
Colorectal cancer (CRC) is one of the most preventable forms of cancer, but it remains a leading cause of cancer associated death. The U.S. Preventive Services Task Force recommends that adults ages 45 to 75 get screened for CRC. According to Derek W. Ebner, M.D., a gastroenterologist at Mayo Clinic in Rochester, Minnesota, participation in CRC screening is improved when a patient's medical team reviews the different types of screening tests available, and then provides the opportunity to choose the strategy that works best for the patient.
However, one factor that can compromise the effectiveness of colonoscopy is the presence of significant interoperator variability in polyp detection rates. This fact led Dr. Ebner and co-investigators to conduct a study that examined whether having pre-procedure knowledge of a positive multitarget stool DNA (mt-sDNA) test improves neoplasia diagnosis rates among colonoscopists with lower baseline adenoma detection rates, independent of withdrawal time. The results of that study were published in Digestive Diseases and Sciences in 2023.
Why is this an important research topic right now?
We know that when individuals pursue colonoscopy, an adequate colon preparation is required, and the proceduralist must meet or exceed certain quality metrics. For example, the rate at which polyps are identified during a screening colonoscopy is an important variable. In fact, this data is monitored for the purpose of quality control and has been shown to protect patients against the development of CRC after colonoscopy. However, there is a lot we do not know about colonoscopists' performance during a follow-up colonoscopy in patients who have a positive stool-based test.
What was the primary question that your research team sought to answer, and how did you design your study to address that?
Our study attempted to address this question: For follow-up colonoscopies after a positive mt-sDNA test, does the diagnosis of polyps increase simply because it is an enriched sample? Previous work by our group, published in Gastrointestinal Endoscopy in 2017, did not necessarily support this. Greater rates of polyp diagnosis were observed when a proceduralist was aware they were doing a colonoscopy after a positive mt-sDNA test, compared with rates of polyp diagnosis that occurred when the colonoscopist was blinded from the mt-sDNA test result. However, we wanted to examine whether these differences were associated with differences among the proceduralists.
To explore this further, we looked at proceduralists who conducted the highest volume of follow-up colonoscopies performed after mt-sDNA testing. We then grouped these individuals based upon their performance during standard screening colonoscopies. Within each quartile of colonoscopists, we analyzed baseline colonoscopy adenoma detection rates (ADRs) and serrated lesion detection rates and compared this data with post-mt-sDNA colonoscopy neoplasia diagnosis rates. We also measured withdrawal times from negative exams.
What were your key findings, and how might these findings guide clinical practice or clinical trials in the future?
What we found was surprising. Although the rates of polyp diagnosis were increased across all groups when colonoscopists had awareness of positive mt-sDNA test results, we observed significantly greater improvement among individuals with the lowest polyp detection at baseline screening colonoscopy.
Among 35 gastroenterologists performing screening colonoscopies, the median adenoma detection rate was 32%, and the median serrated lesion detection rate was 13%. Among gastroenterologists performing follow-up colonoscopies for patients with a positive mt-sDNA test, the median adenoma detection rate increased to 47%, and the median serrated lesion detection rate increased to 31%.
Our work suggests that awareness of a positive mt-sDNA test impacts the behavior of the individual conducting the colonoscopy. Perhaps awareness of the positive mt-sDNA test heightens attention during colonoscopy in an effort to find the cause for the test being positive. Because we evaluated these groups using established quality markers, our study findings have important clinical implications. Specifically, we can help inform anticipated polyp diagnosis rates for follow-up colonoscopy, and this data can be used to monitor colonoscopy quality.
What additional research is needed to further clarify the issues discussed in your article?
Our study was retrospective, so an important next step would be to conduct a prospective study to validate these results. Admittedly, evaluating factors that influence human behavior is challenging to study. However, future technologies may provide additional ways in which this can be measured. In the meantime, our group is continuing to explore the real-world performance of mt-sDNA tests, and we look forward to comparing our findings to mt-sDNA 2.0.
For more information
Ebner DW, et al. Neoplasia diagnosis after multi-target stool DNA is enhanced among lowest baseline detectors. Digestive Diseases and Sciences. 2023;68:3721.
Johnson DH, et al. Multitarget stool DNA test: Clinical performance and impact on yield and quality of colonoscopy for colorectal cancer screening. Gastrointestinal Endoscopy. 2017;85:657.
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