Colorectal cancer: early detection remains the key

With 42,000 new cases every year in France, colorectal cancer is the third most common cancer, responsible for 18,000 deaths, making it the second most deadly cancer after lung cancer in men and breast cancer in women. Yet early detection means that 90% of cases can be cured.

SCREENING NOW SIMPLER

The use of the immunological test for blood in the stools, which has been available since May 2015 and replaced the previous test (Haemoccult), has been accompanied by a doubling of the positive rate, from 2.3% to 4.7%. However, if this improvement in sensitivity is to be fully effective, the participation rate is still insufficient (currently 30%), whereas it should be at least 50% to significantly reduce the incidence of the disease.

In the event of a positive test, a colonoscopy must be performed, which will reveal an "advanced" adenoma or cancer (generally localised) in 35% of cases. In eight out of ten cases, when a polyp is detected, it is benign.

Who is affected?

- If you have symptoms, in particular blood in the stools, but also unusual constipation or diarrhoea, possible pain, weight loss or fatigue, you should seek specialist advice, whatever your age.
- If you have a personal history of polyp or colorectal cancer, specific follow-up is carried out, adapted to each situation.
- If you have a family history of colorectal cancer or polyps, a specialist consultation will help assess your individual risk and suggest a suitable strategy. In some cases, the advice may justify an oncogenetic consultation, which may lead to a family investigation.
- If you have no symptoms or history of cancer and are aged between 50 and 75, the screening test is for you and will be suggested to you by your GP.

Download the Mars bleu leaflet from the Institut national du cancer (Inca) here

COLONOSCOPY: RECENT IMPROVEMENTS

If the screening test is positive, your specialist will suggest a more in-depth clinical examination, known as a colonoscopy. This is currently the only method that can diagnose colon cancer or precancerous lesions and destroy benign polyps.

Photo 1. short-pedicle polyp

Carried out using a probe, colonoscopy consists of a digestive endoscopy to visually examine the rectum and the entire colon. It is performed on an outpatient basis and under anaesthetic.

Preparation

The patient must follow a liquid diet 2 to 4 days before the examination and take a colonic preparation. Conventional preparations (PEG-based) are still highly effective. However, they can be replaced by sodium picosulphate solutions, which are less difficult to absorb and just as effective, provided that the protocol is carefully followed and clearly explained to the patient.

HD endoscopes and electronic staining

The current standard is to use "high definition" endoscopes, which have demonstrated their superiority in screening and detecting lesions. Once the polyp has been located, its characterisation is improved by the use of (electronic) image modifiers that enhance the visibility of the relief or vascularisation. The indications for treatment are more clearly defined, even before the result of the histological analysis of the polyp.

Comfort and safety features

The probe allows a small amount of gas (^CO2) to be blown in during the colonoscopy to loosen the walls, which improves comfort during the examination.

Photo 2. Large "granular" polyp with lateral extension

THERAPEUTIC COLONOSCOPY

Mucosectomy

This technique is particularly suitable for "flat" lesions, which are resected after being elevated by a substance injected under the lesion into the submucosa. Depending on the size and location of the lesion, it may be resected in a single piece ("monobloc") or in fragments, which are then completely examined under microscopy. The base of the lesion may be closed with "clips", which are also useful for controlling any bleeding.

Photo 3. Sessile polyp spread out in a "sheet" over a fold.

Photo 4. The polyp is raised and undergoes "electronic" staining.

Photo 5. It is resected (removed) by mucosectomy.

Submucosal dissection (technique under development)

This technique was initially developed in Japan and is rapidly becoming widely used in Europe. It allows endoscopic "surgery" by dissection under the base of the lesion after, as in mucosectomy, elevation by repeated injections of substances which allow complete detachment from the deep planes. It is particularly suitable for large lesions, with the main advantage over mucosectomy of obtaining a "monobloc" surgical specimen, further improving the quality of microscopic analysis.

Conclusion

The key to improving colorectal cancer screening in the general population is to increase the uptake rate (ideally to over 50%) of the fecal blood test in asymptomatic subjects aged over 50.

In all other cases, the necessary investigations should be carried out, in particular colonoscopy, especially in cases of external bleeding, especially as recent statistics clearly show an increase in the incidence of this cancer in younger people not covered by the usual screening programmes.

Some colorectal cancers are linked to an inherited genetic predisposition. Situations where there is a familial risk should be assessed on an individual basis, if necessary with recourse to a specialist oncogenetic consultation.

In recent years, colonoscopy has undergone significant development, thanks to the use of electronic endoscopes that provide a high level of "standard" image quality, further enhanced by image processing procedures that enable lesions to be characterised very precisely. This is accompanied by new therapeutic procedures that can sometimes be carried out at the same time. In daily practice, they already enable large or extensive polyps to be treated endoscopically, thereby avoiding the need for surgery in many cases.

Improved screening tests and the development of new diagnostic and therapeutic colonoscopy techniques should enable us to combat colorectal cancer more effectively. The earlier it is detected, the better the chances of survival.