The fact that bowel cancer has a recognizable premalignant phase, and that early cancer itself may be cured by surgery, implies that the condition should be amenable to a program of cancer screening, which might substantially reduce mortality from the disease. Bowel cancer screening has been introduced into a number of countries and there is pressure on European governments to follow the lead from the US, where an extensive program is in operation.

In order to assess the implications of bowel cancer screening in Europe, the European Society of Digestive Endoscopy held an international workshop in Oslo, the proceedings of which were published in Endoscopy in 2004.1 This article gives a resumé of the conclusions that were drawn.

The Oslo Workshop
The Oslo workshop focussed on the public–professional interface, which is critical for any cancer screening program. It tackled four areas – methods and economic considerations of screening, the implementation of bowel cancer screening, issues relating to public awareness and lobbying and legal and ethical considerations. Each topic was considered by an individual working party, which presented their findings to a plenary session on which the recommendations were voted to produce a consensus.

Methods and Economic Considerations
Three methods of screening for bowel cancer are currently practiced. They aim to identify early cancer and pre-cancerous polyps in the population at average risk of developing the disease. As this condition only infrequently affects individuals under 50 years-old, most screening programs for the average risk patient start at around that age.

The first method is the examination of a stool sample for occult blood using a sensitive chemical or immunological technique. The concept behind this is that cancers often bleed, and a positive fecal result can be followed up by a definitive examination with a colonoscope, at which stage polyps can be removed, cancers can be detected and the patient can be reassured. Fecal occult blood should be examined-for on an annual basis.

The second method is flexible sigmoidoscopy. Patients are given an enema in order to clear the lower bowel. A flexible endoscope is passed through the back passage through which the lower bowel can be visualized. Between 25% and 30% of the bowel can be inspected in this manner and it is this lower part of the bowel that is most likely to harbor cancers and polyps. Polyps can be removed at the time of the examination and if these are multiple, large, or have worrying microscopic features, full colonoscopy can subsequently be performed.

The advantage of this technique over fecal occult blood is that removal of polyps may prevent future cancers, whereas fecal occult blood testing only usually identifies early cancers, and not polyps, as they tend not to bleed. The procedure is undertaken without sedation making it cheaper, quicker, and safer than colonoscopy. Its disadvantage is that it is not possible to see the whole of the large intestine, so advanced cancers may be present higher up the bowel and may not be identified. Flexible sigmoidoscopy screening should probably be performed every five years.

The third screening modality, colonoscopy, is now the preferred method used in the US. Colonoscopy usually has to be undertaken by a trained gastroenterologist. The patient has to undergo a substantial laxative bowel preparation on the day before the examination. On the day of the examination the patient is usually given an intravenous sedative and the colonoscope is passed through the colon. The whole of the lining of the bowel is inspected for polyps or cancer.