Fecal test levels refine post-polypectomy surveillance

A large population-based study of nearly 90,000 patients found that fecal hemoglobin levels can be used to individualize post-polypectomy surveillance intervals, reducing colonoscopy demand by about 10% without increasing colorectal cancer risk.

In the study, published in Gastroenterology and led by Han-Mo Chiu, MD, PhD, of National Taiwan University Hospital, Taipei, investigators analyzed data from a nationwide fecal immunochemical test screening program to evaluate whether fecal hemoglobin concentration could refine current surveillance recommendations after polypectomy.

Study design and population

The prospective cohort study drew from 3.9 million participants aged 50 to 74 years in Taiwan’s colorectal cancer (CRC) screening program between 2010 and 2015. Among these, 269,600 patients underwent colonoscopy after a positive fecal immunochemical test, and 89,771 patients with adenomas who received polypectomy formed the analytic cohort.

Patients were classified as low risk or high risk based on guideline-defined adenoma features. About half fell into each category. Participants were followed for a mean of 5.5 years, during which 1,413 incident CRCs were identified, corresponding to an overall incidence of 2.8 cases per 1,000 person-years.

The investigators used a time-to-event model to quantify CRC risk across fecal hemoglobin strata and then derived adjusted surveillance intervals. These intervals were shortened for higher fecal hemoglobin levels and extended for lower levels, while remaining within current guideline boundaries.

Key findings

A clear dose-response relationship emerged between fecal hemoglobin concentration and CRC risk after polypectomy. Incidence increased from 2.2 cases per 1,000 person-years at fecal hemoglobin levels of 20 to 49 μg/g to 4 cases per 1,000 person-years at levels of 450 μg/g or higher.

After adjustment for age, sex, and adenoma risk category, patients with the highest fecal hemoglobin levels had about 1.7 times the likelihood of developing CRC compared with those in the lowest group. High-risk adenoma status independently conferred about 1.4 times the likelihood of CRC.

Using these gradients, the authors modeled a precision surveillance strategy. For example, in low-risk patients, surveillance intervals ranged from about 10 years at the lowest fecal hemoglobin levels to about 6 years at the highest levels, compared with the current 7- to 10-year recommendation. In high-risk patients, intervals were shortened toward 2 years for higher fecal hemoglobin levels, although capped at 3 years for clinical feasibility.

When applied across the cohort, this approach reduced colonoscopy demand by 9.8% over 9 years compared with current US Multi-Society Task Force recommendations (160,316 vs 177,766 procedures). Importantly, cumulative CRC risk remained comparable between strategies. Overall risk was slightly lower with the fecal hemoglobin–guided approach (25.2 vs 27 per 1,000), reflecting a projected 6.7% relative reduction.

Subgroup analyses showed similar patterns across adenoma risk groups and by sex. Reductions in colonoscopy use were driven primarily by extending intervals in low-risk patients, while slightly increasing procedures in higher-risk patients with elevated fecal hemoglobin.

Clinical implications

The findings suggest that fecal hemoglobin, already measured in screening programs, could serve as a practical biomarker to refine surveillance timing beyond colonoscopic findings alone.

Patients with low fecal hemoglobin levels after polypectomy may safely undergo longer surveillance intervals, potentially reducing unnecessary procedures. Conversely, those with elevated levels may benefit from earlier follow-up despite similar baseline adenoma classification. According to the authors, this risk-based approach could help address rising demand for colonoscopy by reallocating resources toward patients at higher risk while avoiding over-surveillance in lower-risk populations.

Dr. Chiu and colleagues acknowledged certain limitations of the analysis, noting that it included only patients with conventional adenomas and had limited data on serrated lesions. Also, information on high-grade dysplasia was incomplete, surveillance practices were not standardized across centers, and data on medications that may affect fecal hemoglobin were unavailable.

They concluded that integrating fecal hemoglobin concentration into post-polypectomy surveillance decisions “can optimize colonoscopy resource allocation without compromising colorectal cancer risk reduction.”

The study was funded by Taiwan’s Health Promotion Administration and National Science and Technology Council. The authors reported no conflicts of interest