The efficacy of cap-assisted colonoscopy compared with regular colonoscopy in CRC screening participants.

Colorectal cancer (CRC) is the second most prevalent type of cancer and an important cause of death in the Netherlands. Reduction of the incidence of CRC can be achieved by detection and removal of its precursor lesions, adenomas. In 2005, the Dutch Health Council advised to investigate the implementation of different population screening methods for CRC in the Netherlands. Colonoscopy is widely accepted as the gold standard for detection of colorectal neoplasia. However, a substantial adenoma miss rate of 20-26 % has been reported in tandem colonoscopy studies. This may be due to adenomas situated outside the visual field, either hidden behind folds or at flexures. The use of a transparent hood (“cap-assisted colonoscopy”) could be helpful in detecting and removing colorectal polyps by depressing semilunar folds during inspection. Several studies with drawbacks in study-design failed to demonstrate that cap-assisted colonoscopy increases the adenoma detection rate. If adenoma detection rates are higher in cap-assisted colonoscopy, this would result in a higher yield of CRC screening by colonoscopy and thus lower the incidence of CRC.
In this proposal we aim to compare adenoma– and polyp detection rate in cap-assisted colonoscopy compared with regular colonoscopy in screening participants for CRC. Furthermore, we will analyze the cecal intubation time, polypectomy time, difficulty of different colonoscopic procedures, burden of colonoscopies and complication rates.

All participants will be randomized (1:1) for cap-assisted colonoscopy or regular colonoscopy. The study will be facilitated by the logistic backbone of the screening program for CRC.

Cap-assisted colonoscopy may improve the adenoma detection rate in CRC screening participants.

All individuals planned for CRC screening by direct colonoscopy, will be asked to participate in this study. After obtaining informed consent, colonoscopy will be performed within 4 weeks in one of the two participating centres by professionals with an experience of at least 200 regular and 20 cap-assisted colonoscopies. The colonoscopy will be performed taking the standard quality aspects into account. When performing cap-assisted colonoscopy, a transparent hood is attached at the tip of a cap-fitted colonoscope so that the tip of the hood was 4 mm ahead of the edge of the colonoscope. A side hole on the distal attachment is added to drain fluid during observation and procedure allowing clear endoscopic view. Time to reach the cecum and withdrawal time will be measured by using a stopwatch. Withdrawal time will be at least 6 minutes. Polypectomy time will be calculated by recording the time when passing an instrument through the instrument channel for polypectomy and the time when the polyp has been removed. Of all detected lesions the size, morphology (sessile, pedunculated, flat or depressed), localization and the macroscopic aspect will be noted. All detected lesions will be removed during the same procedure if possible. If immediate endoscopic treatment is impossible, biopsies will be obtained and pathological assessment of these tissue samples will provide a definitive diagnosis. Histology will be processed and stained using standard methods and will be evaluated by expert pathologists. Histology will be defined according to the Vienna criteria. Dysplasia will be defined as either low grade or high grade and all polyps will be classified into hyperplastic, tubular, tubulovillous and villous lesion.
The endoscopist will be asked to asses the difficulty of the polypectomy procedure (in case of polyps > 5 mm), the whole colonoscopic procedure, retroflexion in the lower rectum and ileum intubation by using a 5-points scale.
The burden of colonoscopy will be evaluated by a validated questionnaire, which is part of the screening program for CRC. All complications will be registered in a database until 30 days after colonoscopy.

For this study, all individuals who participate in the pilot study for populationscreening for CRC by direct colonoscopy will be randomized in two different arms:

1. Cap-assisted colonoscopy;

2. Regular colonoscopy.

A total number of 5000 individuals will be invited for our screening program. We expect a participation rate of 25 %, resulting in 1250 participants, 625 individuals in each arm.
The primary outcome of this study is the adenoma detection rate. The study size sample was calculated to be 493 patients. To allow sufficient certainty, the whole group participating in colonoscopy screening will be included in the trial (625 colonoscopies in each arm is expected).