T2021 Higher Cut Off Values for Fit in CRC-Screening: Less Colonoscopies, Same Detection Rates for Curable Cancers

Abstract

Introduction: The Fecal Immunochemical Test(FIT) is a next generation Faecal Occult Blood Test(FOBT)and has been proposed as screening tool for Colorectal Cancer(CRC). The goal of screening is to detect CRC in an early, curable stage(i.e. Dukes A+B). Some variants of FITs produce a quantitative outcome which allows for adjusting the threshold for calling a test positive. A higher cut off value will result in less positive tests and subsequently less screenees referred for colonoscopy and thus less strain on the endoscopic capacity. However it is unknown whether a higher cut off value will impair the detection rate of(curable)colorectal cancers. Aim: To assess the effect of a higher cut off value of a quantitative FIT on the positivity rate and on the detection rate of curable early stage CRC's. Methods: All patients aged ≥18 years and scheduled for a colonoscopy in 5 participating hospitals were asked to perform a FIT(OC sensor®, Eiken chemical Co, Japan) on one bowel movement the day prior to colonoscopy. Tests of all patients were assessed using cut-off values of 50, 100, 150 and 200 ng haemoglobin per ml. For analysis of all tests, the desktop analyser “OCSENSOR μ” was used. Test results were compared with the gold standard colonoscopy. Results: In 1,897 individuals, who underwent total colonoscopy, 62 cases of colorectal cancer(3.3%) were identified. 28/62 patients were diagnosed with early stage (Dukes A+B) colorectal cancer and 31 patients with late stage(Dukes C+D). Three rectal cancers could not be accurately staged due to the effects of neo-adjuvant radiotherapy. In our total population of 1,897 individuals, the OC sensor® was positive in 8.8%, 9.8%, 11.4% and 14.0% at cut offs of 200, 150, 100, and 50 ng/ml, respectively. The detection rates for early stage CRC's ranged from 75.0% to 78.5% depending on the threshold of FIT(Table 1). Conclusions: A higher cut off value for FIT can reduce strain on colonoscopy capacity with only a slight decrease in detection rates of curable, early stage, colorectal cancers.