In a new retrospective analysis of patients with above-average risk of colorectal cancer, multiple negative fecal immunohistochemical tests (FITs) were associated with a lower risk of advanced neoplasia. The findings suggest that multiple negative FITs could potentially identify individuals in high-risk surveillance who aren’t truly high risk, which could in turn ease the logjam of colonoscopies and free resources for truly high-risk individuals.
The study, conducted in Australia, was published online in Clinical Gastroenterology and Hepatology. It included patients who completed at least two FIT exams between surveillance colonoscopies and had no neoplasia or nonadvanced adenoma at prior colonoscopy. Above-average risk was defined as a family history or by findings at surveillance colonoscopy.
The study has some limitations. It is a retrospective analysis between the years 2008 and 2019, and colonoscopy guidelines in the United States have since changed, with a recommendation of surveillance colonoscopy at 7-10 years following 1-2 adenomas discovered at surveillance colonoscopy, and the current study includes follow-up colonoscopy at 5 years. “These data are informative for patients up to 5 years, but they’re not really informative afterwards. They just don’t have those data yet,” said Reed Ness, MD, who was asked to comment on the study.
The authors also don’t describe what they mean by a family history of colorectal cancer risk. “My take was that it’s an interesting result which would seem to support the possibility of returning some patients with a family history or adenoma history to a noncolonoscopy screening regimen after a negative surveillance colonoscopy. We’ll need to see where the data lead us in the future,” said Dr. Ness, who is an associate professor of medicine at Vanderbilt University Medical Center, Nashville, Tenn.
“We’re letting people go 10 years now, and some people are uncomfortable with allowing patients to go 10 years. So you could think of a scenario where you use FIT to try to find people that might have higher-risk lesions that need to come back for colonoscopy within that 10 years,” said Dr. Ness. That issue is particularly relevant given the wide range of adenoma detection rates among gastroenterologists, because FIT could detect a polyp that was missed during a colonoscopy.
The study included two groups with increased risk – those with a family history of colon cancer, and those with previously detected adenomas. The family history cohort may be useful for clinical practice, according to Priyanka Kanth, MD, who was also asked to comment on the study. “Some people may not need [a colonoscopy] at 5 years if they have no polyps found and negative FIT,” said Dr. Kanth, who is an associate professor of gastroenterology at Georgetown University, Washington.
She feels less certain about the group with previously detected adenomas, given the change in U.S. guidelines. “We have already changed that, so I don’t think we need to really do FIT intervals for that cohort,” said Dr. Kanth. “I think this is a good study that has a lot of information and also reassures us that we don’t need such frequent colonoscopy surveillance,” she added.
Steve Serrao, MD, PhD, who was also asked for comment, emphasized the importance of high-quality colonoscopies that reach the cecum 95% of the time, and achieving high adenoma-detection rates. The system can get overwhelmed conducting colonoscopies on patients with good insurance coverage who have already undergone high-quality colonoscopies. “That pushes out patients that haven’t necessarily had a colonoscopy or a FIT. People who don’t have access are kind of crowded out by these false-positive tests. The best modality is actually to do a high-quality colonoscopy and then to have a really well-directed strategy following that colonoscopy,” said Dr. Serrao, who is division chief of gastroenterology and hepatology at Riverside University Health System, Moreno Valley, Calif.
The researchers analyzed data from 4,021 surveillance intervals and 3,369 participants. A total of 1,436 had no neoplasia at the prior colonoscopy, 1,704 had nonadvanced adenoma, and 880 had advanced adenoma. Participants completed no or one to four FIT tests between colonoscopies, with the final colonoscopy performed within 2 years of FIT tests. The median age was 63.9 years; 53.6% were female; 71.1% had a prior adenoma; and 28.9% had a family history of colorectal cancer. A total of 29.4% of participants had one negative FIT; 6.9% had four negative FITs during the interval period; and 31.0% did not complete any FIT tests.
Of follow-up colonoscopies, 9.9% revealed advanced adenomas. Among the patients with no prior neoplasia, those with one negative FIT had a cumulative index function for advanced neoplasia at 5 years of 8.5% (95% confidence interval, 4.9%-13.3%). This was higher than for those with three negative FITs (4.5%; 95% CI, 2.0%-8.6%) or four negative FITs (1.9%; 95% CI, 0.5%-5.0%). The association held for individuals with prior nonadvanced adenoma but not those with advanced adenoma.
Over the 5-year interval, three or more negative FIT tests were associated with a 50%-70% reduction in advanced neoplasia risk at follow-up colonoscopy (P < .001). There was no significant association over a 3-year interval. Dr. Kanth, Dr. Serrao, and Dr. Ness have no relevant financial disclosures.