Colonoscopy Screening: Where Do We Go From Here?

Screening for colorectal cancer (CRC) effective and cost effectiveOne of the earliest tests for colorectal cancer screening is to detect occult blood in the stool and perform a colonoscopy if the test is positive. In an annual randomized clinical trial of fecal occult blood testing in the United States, 18% reduction 18-year follow-up colorectal incidence and 33% reduction Persistent colorectal cancer mortality through 30 years of follow-up. Screening by colonoscopy became popular in the early 2000s, observational study A 60-85% reduction in the incidence of colorectal cancer has been reported.

In the United States, colonoscopy is now the most common screening method for colorectal cancer. It has the advantage of being able to detect not only early cancers but also precursor lesions such as polyps. Therefore, colonoscopy is a tool for early cancer detection and cancer prevention. Despite widespread enthusiasm for colonoscopic screening, data from randomized clinical trials regarding its benefits have been lacking.

Recent colonoscopy results garnered considerable attention Superficially, results are given that suggest colonoscopies are less effective than previously thought. However, this study has some limitations, and if patient screening promotes the atrophic effect, the harm is greater.

Interpretation of the latest colonoscopy studies

of Nord ICC Trial It was a practical randomized trial. test for effectiveness of colonoscopy. Between 2009 and 2014, in this study he randomized 84,585 people to colonoscopy versus usual care (no screening) in his 1:2 ratio. The study reported that colonoscopy screening reduced CRC incidence by 18% and did not reduce CRC mortality, a result that surprises and disappoints readers. I was.

There are three important considerations in interpreting the results. First, this study was intended as a screening trial. This means that individuals randomly assigned to the colonoscopy arm were invited to undergo screening. This demonstrates how randomized trials should and should be conducted to maintain randomization and balance known and unknown confounders. However, the colonoscopy rate was very low, at only 42%. Compare this to the Minnesota Fecal Occult Blood Screening Randomized Trial, which had >84% uptake of fecal occult blood testing followed by colonoscopy. The group randomly assigned to colonoscopy was counted in the denominator regardless of completion, thus showing low utilization of colonoscopy and how the comparison shows a dilution effect. increase. This is when looking at per-protocol or compliance-adjusted estimates. In this trial, the adherent had a 40% reduction in her incidence of colon cancer. Still not as high as expected, but still above 18%.

Second, decades of research on this topic have shown that colonoscopy is highly operator-dependent and that only a high-quality colonoscopy can reduce subsequent colorectal risk. It has been shown to detect and remove early cancer and precancerous polyps that provide protection. As a result, the United States has developed a set of validated quality indicators for the risk of developing colorectal cancer in the near future. The best studied are cecal intubation rate and adenoma detection rate (ADR).the standards we set 95% and 25% respectivelyof these two indicators.

In the United States, many colonoscopies are performed ( 15 million yearly), and we do them well. U.S. endoscopists who perform this procedure most often meet and exceed these criteria. However, the endoscopists in the NordICC study did not meet these criteria. Nearly 30% of her had an ADR <25% and a cecal intubation rate <95%. The study reports only his 35 endoscopists who performed 30 or more colonoscopies during the study period. This casts doubt on the generalizability of the study, particularly to the United States.

Third, the study lacks the ability to detect differences in CRC mortality between the two groups. Colonoscopies detect precancerous polyps that would otherwise take 8 to 20 years to develop into cancer and another 5 to 10 years to progress, spread, and be fatal. Therefore, the benefit of reducing mortality from such lesions is expected to be realized over the long term. With registrations ending in 2014 and follow-up in 2020 (national death registries are generally two years behind), the follow-up period is insufficient to expect differences in mortality risk. The authors continue to follow these individuals and may have more information on CRC mortality at 5 and 10 years. Therefore, conclusions that there is no benefit in CRC mortality are premature.

The final, and perhaps most important aspect of this study is that its generalizability to the entire US population is questionable. The way the study was designed, individuals did not consent (or be informed) to be randomized to colonoscopy or usual care. Therefore, the authors assessed these individuals, including body mass index, baseline colorectal cancer risk, smoking history, and dietary and other lifestyle factors known to be associated with colorectal cancer risk. do not have information about the risk factors for Many subgroups of the US population. Benefits may therefore not reflect efficacy in at-risk populations in the United States. Taken together, it is difficult to see how this applies to our practice.

Put your research in a broader context

Randomized clinical trials are the holy grail of scientific evidence. Estimates from observational studies are generally overstated, and we have repeatedly seen that the tighter rigor of randomized trials makes these estimates smaller and more conservative. hidden assignment Applies. In the context of colonoscopy, we expected some reduction in estimates and more stringent 95% confidence estimates compared to results from observational studies, but this study achieved its goals due to its limitations. it may not have been possible.

Our hope is that this study will be interpreted in the context of the body of evidence on the efficacy of colonoscopy, and that people will see that this is another data point and that more will come from ongoing trials. It’s about getting them to understand that the data is available. We also need to educate the public that screening for colorectal cancer reduces the risk of developing and dying from CRC, and that colonoscopy is a highly effective modality. Clinicians must ensure that patients understand this and continue to encourage screening. Don’t throw your baby out with the hot water yet.

Aasma Shaukat, MD, MPH, Robert M. and Mary H. Glickman are professors of medicine and gastroenterology and directors of outcome studies in the Department of Gastroenterology and Hepatology at NYU Langone in New York City. She is a practicing physician and researcher in colon cancer screening and colonoscopy quality indicators.