Detection of advanced colorectal neoplasia and relative colonoscopy workloads using quantitative faecal immunochemical tests: an observational study exploring the effects of simultaneous adjustment of both sample number and test positivity threshold

The Diagnostic Performance of Fecal Immunochemical Tests for Detecting Advanced Neoplasia at Surveillance Colonoscopy

BACKGROUND & AIMS

An increasing burden on health care resources has resulted in a backlog of individuals requiring colonoscopy, with delays in surveillance possibly detrimental for individuals at increased risk of colorectal cancer (CRC). This study investigated the use of a 2-sample fecal immunochemical test (FIT) to establish those most likely to have advanced neoplasia (AN) and in need of prioritized surveillance colonoscopy.

METHODS

This was a prospective study conducted in the tertiary care setting. Participants completed a 2-sample FIT (OC-Sensor, Eiken Chemical Company) within 90 days of surveillance colonoscopy. The sensitivity of FIT for detection of AN (CRC or advanced adenoma) in moderate- and high-risk individuals was determined at fecal hemoglobin thresholds between 2 and 80 μg/g feces.

RESULTS

A total of 766 patients were included (median age, 66.1 years [interquartile range, 58.1-72.9]; 49.9% male), with AN detected in 8.6% (66/766, including 5 CRC). For moderate-risk individuals (with prior history of adenoma or a significant family history of CRC), sensitivity of FIT for AN ranged from 73.5% at 2 μg/g feces, to 10.2% at 80 μg/g feces. For high-risk conditions (confirmed/suspected genetic syndromes or prior CRC), sensitivity of FIT was similar, ranging from 70.6% at the lowest positivity threshold of 2 μg/g feces, to 11.8% at 80 μg/g feces. Independent variables in the whole cohort for association with detection of AN at surveillance colonoscopy were age (odds ratio, 1.03; 95% confidence interval, 1.00-1.06) and FIT hemoglobin result ≥10 μg/g feces (odds ratio, 1.81; 95% confidence interval, 1.04-3.16).

CONCLUSIONS

The use of FIT before surveillance colonoscopy provides clinicians with insights into the risk of AN. This raises the possibility of a method to triage individuals, facilitating the more efficient management of endoscopic resources.

An efficient strategy for evaluating new non-invasive screening tests for colorectal cancer: the guiding principles

OBJECTIVE

New screening tests for colorectal cancer (CRC) are rapidly emerging. Conducting trials with mortality reduction as the end point supporting their adoption is challenging. We re-examined the principles underlying evaluation of new non-invasive tests in view of technological developments and identification of new biomarkers.

DESIGN

A formal consensus approach involving a multidisciplinary expert panel revised eight previously established principles.

RESULTS

Twelve newly stated principles emerged. Effectiveness of a new test can be evaluated by comparison with a proven comparator non-invasive test. The faecal immunochemical test is now considered the appropriate comparator, while colonoscopy remains the diagnostic standard. For a new test to be able to meet differing screening goals and regulatory requirements, flexibility to adjust its positivity threshold is desirable. A rigorous and efficient four-phased approach is proposed, commencing with small studies assessing the test's ability to discriminate between CRC and non-cancer states (phase I), followed by prospective estimation of accuracy across the continuum of neoplastic lesions in neoplasia-enriched populations (phase II). If these show promise, a provisional test positivity threshold is set before evaluation in typical screening populations. Phase III prospective studies determine single round intention-to-screen programme outcomes and confirm the test positivity threshold. Phase IV studies involve evaluation over repeated screening rounds with monitoring for missed lesions. Phases III and IV findings will provide the real-world data required to model test impact on CRC mortality and incidence.

CONCLUSION

New non-invasive tests can be efficiently evaluated by a rigorous phased comparative approach, generating data from unbiased populations that inform predictions of their health impact.

Prioritisation of colonoscopy services in colorectal cancer screening programmes to minimise impact of COVID-19 pandemic on predicted cancer burden: A comparative modelling study

Objectives

Colorectal cancer (CRC) screening with a faecal immunochemical test (FIT) has been disrupted in many countries during the COVID-19 pandemic. Performing catch-up of missed screens while maintaining regular screening services requires additional colonoscopy capacity that may not be available. This study aimed to compare strategies that clear the screening backlog using limited colonoscopy resources.

Methods

A range of strategies were simulated using four country-specific CRC natural-history models: Adenoma and Serrated pathway to Colorectal CAncer (ASCCA) and MIcrosimulation SCreening ANalysis for CRC (MISCAN-Colon) (both in the Netherlands), Policy1-Bowel (Australia) and OncoSim (Canada). Strategies assumed a 3-month screening disruption with varying recovery period lengths (6, 12, and 24 months) and varying FIT thresholds for diagnostic colonoscopy. Increasing the FIT threshold reduces the number of referrals to diagnostic colonoscopy. Outcomes for each strategy were colonoscopy demand and excess CRC-related deaths due to the disruption.

Results

Performing catch-up using the regular FIT threshold in 6, 12 and 24 months could prevent most excess CRC-related deaths, but required 50%, 25% and 12.5% additional colonoscopy demand, respectively. Without exceeding usual colonoscopy demand, up to 60% of excess CRC-related deaths can be prevented by increasing the FIT threshold for 12 or 24 months. Large increases in FIT threshold could lead to additional deaths rather than preventing them.

Conclusions

Clearing the screening backlog in 24 months could avert most excess CRC-related deaths due to a 3-month disruption but would require a small increase in colonoscopy demand. Increasing the FIT threshold slightly over 24 months could ease the pressure on colonoscopy resources.