A negative result on a screening colonoscopy appears to be highly predictive of no colorectal cancer even when screening intervals exceed 10 years, according to a recent large study. The finding suggests it may be safe to extend the currently recommended screening interval beyond 10 years in patients with a negative exam, particularly those considered to be at low risk.
“This is a very positive study because it really demonstrates the protective power of colonoscopy for substantial periods of time,” said Douglas K. Rex, MD, MASGE, a distinguished professor emeritus at the University of Indiana School of Medicine, in Indianapolis.
Aasma Shaukat, MD, MPH, the Robert M. and Mary H. Glickman Professor of Medicine at the NYU Grossman School of Medicine, in New York City, also interpreted the study as part of an encouraging trend. “For the purpose of guidelines, there has been some discussion in the past whether we could start lengthening intervals for repeat screening colonoscopy. This is definitely a step in the right direction.”
The new study is not the first to indicate that patients who have a negative screening colonoscopy may not need another one for at least 10 years, and that its protective effect might extend beyond a decade. “The same authors published data—though not direct observational data as in this study—suggesting a negative colonoscopy is protective against colon cancer for more than 20 years,” Dr. Rex told Gastroenterology & Endoscopy News (Gastroenterology 2020;159[6]:2235-2237; J Clin Oncol 2011;29[28]:3761-3767).
Another study, carried out by the Polish Ministry of Health, suggested that the protective effect of a negative colonoscopy screening might stretch out as long as 17 years (Ann Intern Med 2020;173[2]:81-91). In addition, a study by Dr. Rex and co-investigators found fewer adenomas and advanced neoplasms (ADNs) in patients undergoing a second screening colonoscopy 10 years after a negative screening colonoscopy than in those undergoing their initial screening colonoscopy in the same practice (Gastrointest Endosc 2018;87[1]:254-259).
“We had a similar finding, but this recent study is more powerful because it has such a large number of patients,” Dr. Rex said.
Rate of ADNs Low After Negative Exam
In the current study, researchers in Germany conducted a registry-based, cross-sectional study of 120,298 patients 65 years of age or older, who had undergone a negative screening colonoscopy at least 10 years before (JAMA Intern Med 2023 Jan 17. doi:10.1001/jamainternmed.2022.6215).
They found a prevalence of ADNs of 3.6% in women and 5.2% in men 10 years after a negative exam. The prevalence increased to 4.9% and 6.6% in women and men, respectively, 14 years or more after a negative colonoscopy. The prevalence of ADNs was consistently 40% lower in women regardless of the length of time between initial and repeat colonoscopy. This sex-related difference was even more pronounced in participants younger than 75 years.
The investigators concluded that the prevalence of ADNs 10 years after a negative screening exam is low, and that extending the recommended screening interval beyond 10 years—especially in women and younger, asymptomatic patients—may be warranted.
The study has some limitations, Dr. Shaukat noted. “This is an observational study, so there’s a potential for selection bias. We don’t know how patients who underwent a repeat colonoscopy at 15 years differ from those who got a second exam at 10 years.”
Also, little is known about the quality of colonoscopies that patients in this registry received, Dr. Shaukat said. But that could be interpreted in a positive light. “Assuming it was a broad spectrum of quality of colonoscopy, that should reassure us that even when we don’t know about the quality of colonoscopy, we can be reasonably sure we’re not increasing the risk of ADN by waiting beyond 10 years.”
She noted that the 10-year interval is one of several quality indicators for colonoscopy, although adherence to it isn’t particularly high among physicians in the United States.
“There’s a lot of data showing that most repeat screening colonoscopies happen about five to seven years after the first exam,” Dr. Shaukat said. “Most of these colonoscopies are of extremely low value. They probably do not contribute to the additional reduction in risk of colon cancer but add cost and risk of complications.
“This study should reassure us that the 10-year interval is safe, and open us to the possibility of lengthening that interval to beyond 10 years, particularly for lower-risk individuals,” she said.
Dr. Rex said he anticipated that as colonoscopy and other forms of colorectal cancer screening continue to evolve and improve, we may reach a point where patients with negative screening exams or minor findings can safely undergo only one or two colonoscopies in their lifetime.
“We have high-definition optics, quality metrics that emphasize the measurement of the adenoma detection rate, progressive rises in ADR, increased attention to the importance of sessile serrated lesions, as well as a bunch of adjuncts to detection,” he said. “And we’re going to see artificial intelligence programs that will measure how well we’re examining the colon and give us real-time feedback. As colonoscopy continues to improve, it will probably be more cost-effective to do it at 15-year intervals, at least by people who are high detectors.”
—Monica J. Smith
Dr. Rex reported financial relationships with Boston Scientific, Braintree, Endokey, Erbe, GI Supply, Medivators, Medtronic, Norgine, Olympus and Satisfai Health. Dr. Shaukat reported financial relationships with Freenome, Iterative Health and Motus.
This article is from the March 2023 print issue.