Trial Information

Adenoma Detection Rate in Rectal Remnants of Familial Polyposis (FAP) Patients Using Standard (White Light), Auto-Fluorescence (AFI), Narrow Band Imaging (NBI) and Chromoscopic Endoscopy

Colorectal cancer is the second commonest cause of cancer death. In majority of cases it is
preceeded by a precancerous lesion called an adenoma (commonly known as polyp). Detection
and removal of adenomas has been shown to reduce the death rate from colorectal cancer.
Despite of meticulous examination "a miss rate" for adenomas at colonoscopy ranges from
6-15% in back-to-back colonoscopy studies. The nature of the polyps, which as well as being
pedunculated (cherry like) can also be flat, which makes it difficult to see and detect and
may add to the"miss rate".

The factors that affect whether an endoscopist sees a polyp are not well studied. Polyp
detection rates vary widely, even amongst experts. Techniques that highlight lesions
advanced in recent years. Chromoendoscopy, spraying dye on the bowel lining, has been shown
to help pick up more precancerous polyps in one of three studies in normal patients.
Autofluorescence endoscopy (AFI) and narrow band imaging (NBI) use 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.

Patients with familial adenomatous polyposis (FAP) have many hundreds of bowel polyps due to
a genetic defect and are at very high risk of colorectal cancer. Many of them have the
majority of the large bowel removed with only lowest part of the large bowel, the rectum,
left and joined to the small bowel. The remaining rectum can still have up to 50 polyps and
is regularly surveilled with sigmoidoscopy to see if any large polyps have grown so they can
be removed before they turn into cancer. Some of these polyps are small and flat.

We aim to see if using the new enhancement techniques we can detect more polyps in patients
with FAP than with standard endoscopy.The patients will undergo flexible sigmoidoscopy as
usual. This will then be repeated with the auto fluorescence feature of the endoscope
activated, followed by a repeat with the narrow band feature activate. Then the lining of
the bowel will be sprayed with blue dye (non-absorbed) and extra dye suctioned, the viewing
process will be repeated the final time. This should take approx. 5 minutes. The videos from
the procedures will be anonymised and randomised for viewing by another endoscopist.