High Definition Endoscopy Versus Virtual Chromoendoscopy In The Detection Of Colonic Polyps In HNPCC
Hereditary non-polyposis colon carcinoma (HNPCC) or the Lynch syndrome is a rare cause of
colorectal cancer caused by a defect in mismatch repair genes. Because of this, colorectal
cancer does not develop according to the classical adenoma-carcinoma sequence, resulting in
faster progression to malignant lesions. As a results patients typically present at a
younger age with colorectal cancer or associated cancers such as endometrium or ovarian
cancer. The risk for cancer in patients with the Lynch syndrome has been estimated to be
60-90% for colon cancer presenting at a mean age of 44 years . Colonoscopy is considered the
gold standard for polyp detection. However the polyp miss rate has been reported to be 2%
for larger adenomas (< 10mm) , 13% for lesions between 5 and 10 mm and up to 26% for small
lesions (1-5 mm). Between 2 to 6 percent of carcinomas can be missed , resulting interval
cancers. Typically, in HNPCC small colorectal lesions can already harbor cancer or high
grade dysplasia, making early detection of small lesions even more clinically relevant than
in an average risk population.
New endoscopic imaging systems that are currently available have a high definition video
signal and have an incorporated feature of virtual chromoendoscopy. High definition
endoscopy is becoming the new gold standard in endoscopy, since it is available in all new
types of commercially available endoscopes. The use of high definition endoscopy may lead to
improved recognition of subtle and flat lesions. Furthermore, the use of filters techniques
accentuates superficial changes in the mucosal architecture and helps to characterize
polyps. I-scan is a postprocessing filter incorporated in the high definition processor
(EPKi) of the new Pentax endoscopes. The techniques highlights changes in surface and
vessel architecture through 3 different modifications (so called surface enhancement, tone
enhancement and contrast enhancement). In a randomized trial in patients with a positive
feces occult blood test it has been shown that the system detects significantly more polyps
than standard resolution white light.
Current literature suggests that classical chromoendoscopy with indigocarmine (Huneberg,
lecomte) or narrow-band imaging (NBI) increases the detection of polyps in HNPCC patients.
Although all of these studies had a cross-over design, randomization for the imaging
modality was either not possible (in case of chromoendoscopy) or not applied (in case of
NBI). So it is not clear whether more polyps are detected by advanced imaging techniques, or
simply by a second inspection of the colon.
The aim of this study was to assess the additional value of i-scan in polyp detection in
HNPCC patients in comparison to high definition white light endoscopy (HD-WLE) in a
randomized controlled cross-over trial. The investigators also wanted to investigate the
effect of a second inspection round on polyp detection.
Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Crossover Assignment, Masking: Single Blind (Subject), Primary Purpose: Diagnostic
The primary endpoint of the study was the difference in adenoma detection between HD-WLE and i-scan, expressed as the miss rate for polyps for each technique.
Primary endpoint is assessed after completion of the trial and inclusion of 60 patients
Raf Bisschops, MD PhD
Belgium: Ethics Committee