Stool blood levels may help tailor colonoscopy follow-up: NTUH study

Taipei, July 14 (CNA) The amount of hidden blood detected in stool tests could help doctors decide when patients need another colonoscopy after polyp removal, according to a study led by National Taiwan University Hospital (NTUH), which found higher levels were linked to about 1.7 times the colorectal cancer risk.

"We aimed to answer a very practical clinical question: after polyp removal, how long should patients wait before undergoing their next colonoscopy? The answer should not be a one-size-fits-all approach," Chiu Han-mo (邱瀚模), director of NTUH's Health Management Center, said at a press conference in Taipei on Monday.

He said the study showed a clear "dose-response" relationship between fecal hemoglobin concentration and future colorectal cancer risk, meaning that "the higher the concentration, the greater the subsequent risk."

The finding could be particularly relevant in Taiwan, where colorectal cancer claimed 7,146 lives in 2025, making it the country's third-leading cause of cancer death after lung and liver cancer, according to Ministry of Health and Welfare data.

Using fecal hemoglobin levels to guide follow-ups could also help Taiwan make better use of the country's limited colonoscopy capacity, as positive fecal immunochemical test (FIT) results -- indicating hidden blood in stool -- generally prompt a diagnostic colonoscopy.

Around 400,000 colonoscopies are performed in Taiwan annually by just over 600 endoscopists, equivalent to about 666 procedures per physician, according to figures presented by Chiu, who described the workload as heavy and staffing tight.

Nationwide screening data

The study analyzed records from 3,929,387 people who underwent FIT screening under Taiwan's national colorectal cancer screening program between 2010 and 2015.

Among them, 89,771 people aged 50-74 had positive FIT results, underwent a complete colonoscopy, had polyps removed, and were followed for an average of 5.5 years.

After adjusting for age, sex and adenoma risk category, participants with fecal hemoglobin concentrations of at least 450 micrograms per gram of feces had 1.72 times the risk of developing colorectal cancer after polyp removal as those with concentrations of 20-49 micrograms.

Chiu said post-polypectomy surveillance guidelines generally followed in Taiwan set follow-up intervals mainly according to the number, size and pathological characteristics of removed polyps, without considering fecal hemoglobin concentrations.

Under those guidelines, patients are classified into two broad risk groups: low-risk patients, who are generally advised to undergo another colonoscopy in seven to 10 years, and high-risk patients, who are advised to return after three years.

Tailoring follow-up to individual risk

The researchers proposed adding the fecal hemoglobin concentration recorded in the positive FIT that led to the diagnostic colonoscopy to create more finely stratified follow-up intervals better aligned with each patient's risk.

Under their statistical model, a low-risk patient with a relatively low level of blood in the stool could wait up to 10 years for another colonoscopy, while one with a higher level could return after six or seven years.

High-risk patients could undergo a follow-up after two or three years, depending on their fecal hemoglobin level, according to the study.

Among the 89,771 patients in the study cohort, the model projected that 160,316 follow-up colonoscopies would be needed over nine years if the precision strategy were adopted, compared with 177,766 under current guidelines, a reduction of 9.8 percent.

The reduction came mainly from less frequent examinations among low-risk patients, whose projected colonoscopy demand fell by 39 percent, while demand among high-risk patients remained virtually unchanged.

The model also projected a 6.7 percent reduction in overall colorectal cancer risk compared with the current guidelines.

Gradual path to clinical adoption

Although the study was published online in the medical journal Gastroenterology on April 1, Chiu said the proposal to use fecal hemoglobin levels to guide follow-up colonoscopy intervals remained at the "advocacy" stage, with no timetable for clinical use.

Health Promotion Administration officials are aware of the findings, but the approach would first need to be validated in a separate group of patients before broader adoption, he added.

Implementation would likely be gradual, Chiu said, with a possible first step being to shorten follow-ups from three years to two for high-risk patients with high fecal hemoglobin levels.

Longer intervals for lower-risk patients could be considered only after the approach gains wider acceptance, he added, as some may be reluctant to wait seven or eight years for another colonoscopy despite their low estimated risk.

"We have provided the scientific basis, but whether patients are willing to accept the approach will require dialogue between doctors and patients," Chiu said.