Oort
15-2-2016
Higher cut off values for FIT in CRC-screening:
less colonoscopies, same detection rates for
curable cancers.
F.A. Oort [1], J.S. Terhaar sive Droste [1], R.W.M. van der Hulst [2], H.A. van Heukelem [3],
R.J.L.F. Loffeld [4], I.C.E. Wesdorp [5], I. Ben Larbi [1], S.L. Kanis [1], M. Neerincx [1],
M.Räkers [1], V.M.H. Coupe [6], G.A. Meijer [7], C.J.J. Mulder [1]
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.
Oort
15-2-2016
Cut off value of Fecal Immunochemical Test
≥ 50ng/ml
≥ 100ng/ml
≥ 150ng/ml
≥ 200ng/ml
Positivity rate
14.0%
11.4%
9.8%
8.8%
Absolute numbers
265/1897
217/1897
185/1897
167/1897
Detection rate of
early stage CRC
78.5%
75.0%
75.0%
75.0%
Absolute numbers
22/28
21/28
21/28
21/28
Table 1 - Positivity rates and detection rates of early stage CRC’s at 4 cut off’s of FIT
[1] Gastroenterology and Hepatology, VU University Medical Center, Amsterdam
[2] Gastroenterology and Hepatology, Kennemer Gasthuis, Haarlem
[3] Gastroenterology and Hepatology, Slotervaart Hospital, Amsterdam
[4] Internal Medicine, Zaans Medical Center, Zaandam
[5] Gastroenterology and Hepatology, Sint Lucas Andreas Hospital, Amsterdam
[6] Epidemiology and Biostatistics, VU University Medical Center, Amsterdam
[7] Pathology, VU University Medical Center, Amsterdam