SIGGAR

Overview

The Special Interest Group in Gastrointestinal and Abdominal Radiologists (SIGGAR) study was two randomised controlled trials that took place between 2004 and 2007. It compared three methods for diagnosing bowel cancer. These methods are described below.

Why was this study needed?

When a person visits their doctor with symptoms that could be signs of bowel cancer, the doctor might refer them to hospital for further checks and tests. Often people will be offered a test to examine the whole of the large bowel to look for anything unusual.

Before this study, the most common tests for examining the large bowel were colonoscopy and barium enema (see below for descriptions). A third option called Computed Tomographic Colonography (CTC) was a relatively new test. Back then there was little scientific evidence on how effective the CTC test was compared to the other tests.

What is a colonoscopy?

A colonoscopy is a type of camera examination. A doctor passes a camera on the end of a thin tube into a sedated patient’s bottom and up into the bowel to look for any cancer and polyps (which can turn into cancer).

What is barium enema?

In a barium enema test a person’s bowel is filled via their bottom with a special white liquid called barium. Special pictures called radiographs are then taken using radiation, such as x-rays. These bowel pictures are examined to see if they show anything unusual in the bowel.

What is a CTC?

A CTC test uses an X-ray scanner to examine the large bowel for anything unusual. A CTC is also referred to as a virtual colonoscopy. A CTC uses the x-rays taken to create 3D images of the bowel. It does not require sedating the patient or inserting anything into their bowel.

What were the aims of the SIGGAR study?

The SIGGAR trials aimed to examine whether a CTC could be used as an alternative to colonoscopy or barium enema.

Prior to the SIGGAR study it was thought likely that CTC was a useful test for examining people with bowel cancer symptoms and might have some benefits over barium enema and colonoscopy. However, there was no strong scientific evidence to support adopting CTC widely.

The SIGGAR study aimed to provide the evidence needed to support the use of CTC in bowel cancer diagnosis.

How was the study carried out?

To achieve the study aims, we compared CTC with barium enema and CTC with colonoscopy in two separate studies to see how effective and safe CTC was compared with the other two tests.

Once a doctor confirmed a patient wanting to take part was eligible for the study, a computer programme randomly assigned them to receive either a CTC, barium enema or colonoscopy examination.

A total of 5,384 patients participated in the two trials. The trial comparing CTC with barium enema involved 3,804 patients. The trial comparing CTC with colonoscopy involved 1,580 patients.

When and where did the study take place?

People were recruited to the SIGGAR trials from 21 NHS hospitals across England between March 2004 and December 2007. For a list of the hospitals see Protecting your data.

Who funded the SIGGAR trials?

The SIGGAR study was funded by the NIHR Health Technology Assessment (HTA) Programme.

What are the results of the study and what impact have they had?

The findings from the SIGGAR trials were published in 2013 in the NIHR-HTA Journals Library website, and in The Lancet for the CTC versus colonoscopy trial and the CTC versus barium enema trial. Imperial College London also published a news article.

The SIGGAR trials showed that CTC was better than barium enema for the diagnosis of bowel cancer. CTC was also better value for money for the NHS. As a result of these findings, the number of barium enema tests offered on the NHS has reduced.

The SIGGAR trials also showed that CTC was generally as good as colonoscopy at finding bowel cancer. It had the added benefit of being a more acceptable test for many people and had fewer complications.