A French study challenges the three-month rule after a positive FIT, but an Australian expert warns against relaxing targets.
A nationwide French study has challenged long-standing assumptions about how quickly patients need a colonoscopy after a positive bowel screening test.
The study found no evidence that waiting longer than the commonly recommended one to three months for colonoscopy after a positive faecal immunochemical test adversely affects colorectal cancer outcomes.
Leading Australian gastroenterologist Professor Alex Boussioutas, director of Gastroenterology, The Alfred and Professor Central Clinical School, Monash University, and head of GI Risk Management, Peter MacCallum Cancer Centre, said the results needed to be treated with caution.
“It’s [the study] is reasonably well done but it’s completely antithetical, it’s completely the opposite of what we would expect and what almost every other study has actually shown,” he told Oncology Republic.
However, he did say there were some positive take-homes from the study, especially for patients who had returned positive FIT results but remained asymptomatic.
“The median time for colonoscopy is 62 days [after a positive screening test in Australia], which is pretty good across the country,” he said.
“I don’t think any health service realistically can get 30 days, which is what we’re meant to do, and the reassuring thing of this study that that we’ve probably got a bit more time.
“We’ve probably got 60 to 90 days of leeway, and we probably shouldn’t stress out about doing it within 30 days.
“The earlier the better, sure. But I guess what this paper is saying is that, you know, maybe we don’t keep chastising ourselves of not doing it for 30 days because no one can get there.”
According to the researchers, whose paper was published in BMJ Gut, colorectal cancer screening protocols in several countries advise that individuals with a positive faecal immunochemical test (FIT) undergo colonoscopy within one to three months.
The rationale has been to minimise the risk of progression during the interval. Yet given that most colorectal cancers develop over years rather than weeks, the clinical urgency of such short timelines has remained uncertain, particularly in health systems facing endoscopy capacity constraints.
In the retrospective cohort study, researchers analysed nationwide data from France covering 2016 to 2019.
The study included 374,113 individuals with a positive FIT result who underwent colonoscopy within 24 months. Compliance with colonoscopy after a positive FIT was high at 86.6%, and the investigators identified 21,616 colorectal cancers and 122,359 advanced adenomas during follow-up.
Using a two-to-three-month interval between positive FIT and colonoscopy as the reference category, the researchers assessed risks of colorectal cancer, advanced-stage colorectal cancer and advanced adenoma across longer waiting intervals up to 24 months.
After adjustment for individual and socio-geographic characteristics, they found no increased risk associated with delays beyond three months.
For colonoscopies performed 12 months or later after a positive FIT, the adjusted odds ratio for colorectal cancer was 0.93 (95% CI 0.83 to 1.03), for advanced-stage colorectal cancer 1.04 (0.85 to 1.25) and for advanced adenoma 0.88 (0.82 to 0.93), compared with the two to three months group.
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Across the full three to 24 months range, no excess risk of cancer or advanced-stage disease was observed.
“Our findings do not support the previous consensus and suggests that the aim of health policies may no longer focus on an ideal one-three month time to colonoscopy after a positive FIT result, as recommended by most guidelines, but rather to ensure that every individual with a positive FIT result uptake colonoscopy,” the researchers wrote.
They said their findings suggested that, at least within a 24-month window, extended intervals did not translate into more advanced pathology at diagnosis.
“This is obviously not a reason to recommend waiting two years before performing a colonoscopy,” the researchers concluded.
“For us, performing the colonoscopy within one-three months after the positive FIT result is too stringent a time target.
“Based on our results, we suggest that the priority in all CRC screening programs is not to focus on the time to follow-up colonoscopy, but to ensure that every participant with a positive FIT result complies with colonoscopy.”
The study also highlighted the prognostic importance of faecal haemoglobin concentration.
Individuals with f-Hb levels of 200µg/g or higher were eight times more likely to have colorectal cancer, 11 times more likely to have advanced-stage colorectal cancer and twice as likely to have advanced adenoma compared with those in the 30–40µg/g range. These data reinforce the potential value of risk stratification based on quantitative FIT results.
In addition to maximising compliance with colonoscopy after a positive FIT, the researchers said it might be worth considering prioritising patients with the highest faecal haemoglobin concentrations for earlier procedures while maintaining efforts to ensure that all FIT-positive individuals ultimately complete diagnostic evaluation.
Professor Boussioutas said he was concerned that health bureaucrats might latch onto studies like these and reduce the benchmarks for colonoscopy timing. He agreed with the sentiment that routine 24-month waits for a colonoscopy was not ideal.
“The message here is don’t take your foot off the accelerator. This is not a sign to actually relax on colorectal cancer,” he said.
“We’ve still got the highest rates in the world. I mean, since our screening program, amazingly we’re starting to turn the corner in terms of our rates.
“Getting screening happening and good colonoscopy, that’s the other key here to be able to diagnose in a timely way.”
