Serial FIT analysis in CRC
Research type
Research Study
Full title
Serial Faecal Immunochemical Testing in patients with Colorectal Cancer
IRAS ID
262746
Contact name
James Bailey
Contact email
Sponsor organisation
Nottingham University Hospitals NHS Trust
Clinicaltrials.gov Identifier
Duration of Study in the UK
2 years, 0 months, 5 days
Research summary
Research Summary
The study proposed is an investigation of the faecal immunochemical test (FIT) in colorectal cancer. NICE guidelines (DG30) recommend the use of FIT tests in primary care to guide referrals for suspected colorectal cancer (CRC) in certain symptomatic patients. FIT tests are a more accurate and convenient form of the Faecal Occult Blood Test (FOBT) and have shown promise as a screening tool for colorectal cancer as well as an investigation for symptomatic patients.
Questions have been posed about the potential for cancers to be missed by a single FIT test, and about factors like patient medications which may produce false results. Whether repeating FIT tests improves the diagnostic accuracy of the test is unclear. Recent studies in the field have investigated repeated FIT tests but have not determined an appropriate interval between tests, nor have they answered questions about the effects of patient/medication/other factors on the reliability of FIT.
This project aims to determine the occurrence of a negative FIT result in patients with an established diagnosis of colorectal cancer. Participants who join the study will be asked to complete and return two FIT samples in the first week following their diagnosis, then one sample per week for three further weeks. The results will be analysed to explore whether repeated tests could reduce the chance of missing cancers.
Patient demographics, medical history, medication history, and biopsy/pathology results will be recorded to evaluate factors which may affect the reliability of FIT tests for CRC.
Summary of Results
44 participants out of 50 recruited returned their signed consent forms and FIT samples for inclusion in the final analysis. The median FIT result for the 1st sample returned was 552.4 (IQR 56.8-1916.8). A positivity threshold of 4 μg Hb/g faeces would have yielded no false negative results. A positivity threshold of 10 μg Hb/g faeces would have yielded 2 false negative results. 43 participants returned their 2nd FIT sample. The median FIT result for the 2nd sample was 2366 (87-1129.6). A positivity threshold of 4 μg Hb/g faeces would have yielded no false negative results. A positivity threshold of 10 μg Hb/g faeces would have yielded 2 false negative results. 43 participants returned their 3rd FIT sample. The median FIT result for the 3rd test was 361.8 (57.8-1271.6). A positivity threshold of 4 μg Hb/g faeces would have yielded 2 false negative results. A positivity threshold of 10 μg Hb/g faeces would have yielded 6 false negative results. 39 participants returned their 4th FIT sample. The median FIT result for the 4th test was 269.8 (42.8-1256.4). A positivity threshold of 4 μg Hb/g faeces would have yielded 2 false negative results. A positivity threshold of 10 μg Hb/g faeces would have yielded 2 false negative results. 30 participants returned their 5th FIT sample. The median FIT result for the 5th test was 180.3 (42.2-772.4). A positivity threshold of 4 μg Hb/g faeces would have yielded 3 false negative results. A positivity threshold of 10 μg Hb/g faeces would have yielded 5 false negative results.
40/44 participants also returned a FIT sample as part of their clinical investigations prior to CRC diagnosis. 25 of these participants completed the FIT after symptomatic presentation and 15 completed a FIT as part of the BCSP. The remaining 4 patients that were diagnosed with CRC did not complete a FIT during their initial investigations. A positivity threshold of 4 μg Hb/g faeces would have yielded 2/40 false negative results. A positivity threshold of 10 μg Hb/g faeces would have yielded 2/40 false negative results.
The median stage of disease at the time of diagnosis was T3 (IQR 2-3). 4 participants had been diagnosed with T1 disease, 14 with T2, 20 with T3 and 6 with T4 disease. 19 patients in the study had nodal disease (N1 or N2) and 5 patients had metastatic disease (M1).
20 patients in the study were diagnosed with rectal cancer (Table 11). 8 patients had sigmoid cancer, 7 had caecal cancer, 3 had CRC affecting their ascending colon, 4 hepatic flexure, 3 transverse colon, and 1 affecting the splenic flexure.
Table 11 shows the chance of a falsely negative test “missing” a CRC at different positivity thresholds. Participants had a 4.5% chance of a false negative from returning a single sample where a threshold of 10 µg Hb / g faeces was applied. This increased to 9.1% and 13.6% for thresholds of 20 µg Hb / g faeces and 40 µg Hb / g faeces respectively. The addition of a second sample reduced the occurrence of false negatives to 0 for thresholds of 10 µg Hb / g faeces and 20 µg Hb / g faeces. Further samples decreased the chance of a falsely negative result with a threshold of 40 µg Hb / g faeces but did not eradicate the risk entirely.REC name
East Midlands - Nottingham 1 Research Ethics Committee
REC reference
20/EM/0076
Date of REC Opinion
11 May 2020
REC opinion
Further Information Favourable Opinion