When a person visits their doctor for symptoms that are suggestive of bowel cancer, the doctor might refer them to hospital for further investigations. Often people will be offered a test to examine the whole of the large bowel to look for abnormalities. Prior to the SIGGAR study, the tests that had proven most suitable for ‘whole colon’ examination were colonoscopy and barium enema.
Colonoscopy is a procedure during which, usually under sedation, a tube (endoscope) with a small camera attached is inserted into the rectum and guided through the large bowel to examine its surface for abnormalities. The barium enema examination involves passing a white liquid containing barium into the bowel through the rectum and then taking x-rays of the bowel.
More recently, a new imaging test for examining the bowel has been developed. This test is called Computed Tomographic Colonography, which you might see abbreviated as CTC or called ‘virtual colonoscopy’. Virtual colonoscopy uses x-rays to take images of the bowel, and creates 3-dimensional pictures to aid diagnosis. It does not require barium.
Prior to the SIGGAR study it was thought likely that virtual colonoscopy was a useful test for examining people with bowel cancer symptoms, and might have some benefits over barium enema and colonoscopy. However, the strong evidence that was needed to adopt virtual colonoscopy more widely had not been collected.
The SIGGAR study aimed to provide the robust evidence needed to support the use of virtual colonoscopy in bowel cancer diagnosis. To achieve this, we compared virtual colonoscopy with barium enema or colonoscopy in two randomised trials, to see how effective and safe virtual colonoscopy was compared with the other two tests.