Impact of time between faecal immunochemical tests in colorectal cancer screening on screening results: A natural experiment

Abstract

Repeated rounds of faecal immunochemical testing (FIT) for occult blood is a common method for screening for colorectal cancer (CRC). However, the time interval between FIT rounds is not thoroughly investigated. In a CRC screening trial in South‐Eastern Norway, individuals were invited for biennial FIT between 2012 and 2019. The positivity threshold was >15 mcg haemoglobin/g faeces (mcg/g). Due to organizational challenges, the interval between screening rounds randomly varied between 1.5 and 3.5 years, forming a natural experiment. We investigated the detection rate of CRC and advanced neoplasia (AN: CRC or advanced adenoma) at the subsequent round (FIT2), according to the faecal haemoglobin concentration (f‐Hb) at the initial screening round (FIT1), and time between the two screening rounds. 18 522 individuals with negative FIT1 who attended FIT2 were included in this study. 245 AN were detected at FIT2, of which 34 were CRC. The CRC detection rate at FIT2 for participants with FIT1 = 0 mcg/g was 0.09% while it was 0.28% for participant with 0 > FIT1 ≤ 15 mcg/g; odds ratio (OR) 3.22, 95% CI 1.49‐6.95. For each 3 months' increment between FITs, the OR for detecting CRC was 1.33 (95% CI 0.98‐1.79), while the OR was 1.13 (1.02‐1.26) for AN. Individuals with FIT1‐value of 0 mcg/g, had a lower AN detection rate compared with participants with 0 > FIT1 ≤ 15 mcg/g, irrespective of time between tests. Although CRC and AN detection rates increase with increasing time interval between FITs, individuals with undetectable f‐Hb at first screen have substantially lower risk of CRC at the next screening round compared with individuals with detectable f‐Hb.

Interval Cancer in Population-Based Colorectal Screening Programmes: Incidence and Characteristics of Tumours

“…We observed differences in the likelihood of developing IC based on the amount of Hb found in faeces in the last screening test before IC is detected. This reinforces the conclusions of other studies that screening programmes could be further optimized by stratifying risk, taking into account the amount of Hb detected in faeces in previous rounds of screening [24]. Differences in the amount of Hb in faeces suggest that changes in the cut-off point for determining a positive result could influence the IC rate, as observed in other research [11,25].…”

“…With respect to Hb in faeces in previous rounds of screening, one study observed that CRC is less likely to be detected in a subsequent round of screening and that individuals with an undetectable amount of Hb in faeces (0) in the previous round of screening presented a lower risk than individuals with a detectable amount of Hb in faeces (>0) [24]. In our study, we observed that screening results influence the risk of developing IC, thereby supporting the idea of this study.…”

Early Screening of Colorectal Precancerous Lesions Based on Combined Measurement of Multiple Serum Tumor Markers Using Artificial Neural Network Analysis

“…Currently, widely used clinical methods for CRC screening include endoscopy, stool examination, imaging modalities, and tumor biomarker detection [3]. Colonoscopy, the gold standard for CRC diagnosis, has superior sensitivity for CRC and advanced adenomas (AA), but it is invasive, inconvenient, associated with complications, and more expensive than alternative methods such as the fecal immunochemical test (FIT) and the guaiac fecal occult blood test (gFOBT) [4]. These factors limit the application of endoscopy in early screening for CRC, especially in China, which has an enormous population.…”