Chapters Index (French) French Version Welcome page Contact

From its well known evolution from a simple adenoma towards colic cancer through multiple steps separated by relatively long periods of time, colo-rectal cancer should constitute an ideal model for setting up a screening policy.

The above diagram details the various molecular steps involved in colon carcinogenesis.

The problem for a good screening policy is to find an easy, reproducible test, well accepted by healthy individuals and not subject to too many false positive or false negative results.

In fact, two methods are proposed:

• the systematic research of fæcal bleeding (with various modalities),
• systematic colonoscopy.

Some very particular studies, in very selected populations abroad (see Nottingham experience and Minnesota experience) and also in France (Burgundy and Calvados experiences) have shown a reduction in mortality using the Haemoccult II test.

However, compliance to the test has always been a problem. Healthy people find the stool collection procedure very unpleasant and are difficult to motivate. Moreover, physicians often lack confidence in this method given that around half of the negative test results could in fact be false negatives, since adenoma and even adenocarcinoma do not regularly bleed.

Systematic endoscopy, even at a less frequent rate (once every five years) is difficult to achieve due to the small number of gastro-enterologists, the examination cost and the discomfort it causes, which all prevent its regular repetition.

For patients having genetic or family predisposition to colo-rectal carcinoma, screening should be more rigorous and involve endoscopy.

It is therefore difficult to obtain a clear recommendation for colo-rectal cancer screening. Patients should be informed of the possibility of Haemoccult II, but a clear explanation of the test should be given (its value, its limits). In fact, among patients with a negative Haemoccult II test, colo-rectal cancer incidence is approximately half that of the normal population (Bouvier et al.). It is only through clear dialogue and informed patient consent that both the general practitioner and the patient can be protected from false interpretations. It is quite interesting to visit the NIH website and try to understand whether, as an individual, one should have a faecal blood test or not!

If the patient is particularly anxious about colon cancer and has objective reasons to fear the development of polyps, it might be safer for the physician to ask a gastro-entorologist for advice, and to propose a colonoscopy.