Trial Information

Randomised, Controlled Trial of Narrow Band Imaging (NBI) Versus Standard Endoscopy for Adenoma Detection

Colorectal cancer is the second commonest cause of cancer death. In a majority of cases it
is preceded by a precancerous lesion called an adenoma (polyp). Detection and removal of
adenomas at colonoscopy has been shown to reduce the death rate from colorectal cancer.
However, despite meticulous examination there is a "miss rate" for adenomas at colonoscopy
which ranges from 66-25% in back-to-back colonoscopy studies. The nature of the polyps which
as well as being pedunculated (cherry like) can be flat or depressed making them difficult
to see, which may contribute to the "miss rate".

The factors, which influence the endoscopist detection are not well studied. Polyp detection
rates wary widely, even among experts. Techniques that highlight lesions have advanced in
recent years. Chromoendoscopy, the current gold standard technique, relies on spraying dye
on the bowel lining, has been shown to help pick up more pre-cancerous polyps in two of
three studies; however it is not widely used as it is time consuming and requires extra
equipment and training. Narrow band imaging (NBI) is a technique that relies in light
filters to improve contrast for the smallest blood vessels in the bowel lining which shows
up adenomas as they have a richer vascular network. It is sometimes described as "digital
chromoendoscopy" as the images produced are similar to chromoendoscopy, but it is much
simpler and quicker to use. Autofluorescence endoscopy uses short wavelength light and light
filters to produce a false colour image of the bowel lining where polyps stand out. These
techniques have been used with some success in the oesophagus and stomach but little work is
available for the colon.

We aim to see if NBI is better than standard colonoscopy for detecting precancerous polyps.
This is likely as it is similar to chromoendoscopy which is already shown to help. If a
polyp is found we will use other types of endoscopy, particularly NBI with magnification and
autofluorescence to see if these techniques are helpful for discriminating between
pre-cancerous and non pre-cancerous polyps.

May 2007 protocol minor amendment: additional viewing by endoscopists outside St Mark's ro
allow assessment of inter- and intra-observer variability. No additional data collected.