Early detection of colorectal cancer

Bowel cancer is usually not noticeable for a long time. Nevertheless, both the preliminary stages of the disease and colorectal cancer can almost always be found – provided you look for them.

This is what happens during “early detection”

In Switzerland, it is recommended for all people between the ages of 50 and 69 who have no symptoms that indicate colorectal cancer. However, it is possible that these age limits will shift in the future, partly because colorectal cancer is currently becoming more common in younger people and partly because people up to the age of 75 also benefit from early detection.

There are currently seven methods for detecting bowel cancer before it becomes apparent. Two of these, the blood in stool test and colonoscopy, are recommended for early detection in Switzerland because they offer the greatest benefit and have been scientifically well tested. In terms of costs, both are comparable when calculated over the years.

The so-called “opportunistic” screening takes place outside of these screening programs. Each person goes to the screening examination individually; data on successes and complications are not systematically recorded and are therefore not known.

What are the benefits of regular screening tests for bowel cancer? The bare figures look like this:

A closer look reveals that many of the bowel tumors discovered during a screening examination are still easily treatable. In a US study, for example, almost 40 percent of the tumors diagnosed in this way were still in stage 1, i.e. they could usually be cured with surgery. Of the colorectal cancers that made themselves felt through symptoms, only around seven percent were still in stage 1.

Nowadays, bowel cancer has a good prognosis if it is detected early. However, in every fifth person affected, the cancer has already metastasized at the time of diagnosis.

If all people over the age of 50 – i.e. when the likelihood of colorectal cancer increases – took up the early detection offers, the mortality rate from colorectal cancer could be reduced. This has been proven for the sigmoidoscopy (“small” colonoscopy) and the test for blood in the stool. Studies are still underway to provide this evidence for the “large” colonoscopy. However, it can be strongly assumed that colonoscopy is at least as effective as the “small” colonoscopy.

The disease rate can also be reduced with colonoscopy, but not with the test for blood in the stool. This is because colonoscopy detects and removes intestinal adenomas, i.e. the precursors of colon cancer.

However, early detection measures not only have advantages but also disadvantages:

• They can give false results, so that the person concerned is either lulled into a false sense of security or unnecessarily frightened and needs further clarification until it is clear that they do not have bowel cancer.
• They can cause complications.
• Although they ensure that the disease is recognized earlier, they cannot change its course. Although most people benefit from early detection, for some it can mean that they live longer knowing they have a non-curable disease and may also receive more treatments that affect their quality of life. It is also possible that bowel cancer would not have caused any symptoms until the end of life if it had not been detected.

After weighing up all the advantages and disadvantages, experts in all Western countries have come to the conclusion that the benefits outweigh the disadvantages and recommend early detection.

When deciding on an examination, it is important to decide whether you prefer

• choose the more effective but more unpleasant examination method – colonoscopy – and then do not need another screening examination for ten years (if nothing abnormal is found).
• chooses the less good but more pleasant examination – the test for blood in the stool – with the risk that, depending on the result, a colonoscopy may still be necessary.

At very low risk, the various early detection methods are about equally good. However, the higher the risk of disease, the more likely it is that colonoscopy will be chosen.

What can I do?

No matter what you decide: Early detection is all the more effective the more consistently it is carried out. A single examination is less effective than those that are carried out regularly – every two to ten years, depending on the method.