As the 2022 edition of the Mars Bleu operation launched to improve screening for colorectal cancer, which affects nearly 45,000 people in France each year, is coming to an end, the participation of the population concerned in this prevention operation has reached barely 35%. “A real problem”, for Professor Jean-Baptiste Bacher, gastroenterologist at the Parisian hospital of Pitié-Salpêtrière.
– Why Doctor: we are coming to the end of “Mars Bleu” which aims to encourage screening for colorectal cancer. Why is this operation important?
Pr Jean-Baptiste Bachet: Screening is the best way to reduce mortality from colorectal cancer by making earlier diagnoses, whether of cancers or preneoplastic lesions such as polyps. This makes it possible either to prevent the occurrence of cancers by treating polyps which have not yet degenerated or to make cancer diagnoses at an earlier stage with more possibility of curing them by combining surgery and adjuvant chemotherapy. There are several national and international epidemiological studies which have demonstrated that this strategy of screening by an immunological test followed by a colonoscopy made it possible to reduce mortality from colorectal cancer.
– How can this low adherence to this program be explained?
It’s a real problem. The French are less compliant than the inhabitants of Nordic or Anglo-Saxon countries, which poses a real problem since this screening represents a fairly substantial national investment on the part of the State and because it is, it must repeat, the best way to reduce colorectal cancer mortality. Yet there is a lot of communication about this screening but despite this people do not participate enough. Is it related to the problem of stools…
– What are the different techniques used for this screening?
Currently, for screening methods, there are several things: first, we define populations according to different risks, people who have a personal or family history of polyps or colorectal cancer, people who are affected by rare genetic syndromes favor colorectal cancer, must have colonoscopies. For them the risk is relatively high and we cannot rely on the immunological test for screening. Then we have the population at average risk and we cannot perform a colonoscopy on everyone because it is an invasive procedure with general anesthesia and there is a risk of complications. For this category, there is the immunological test with search for the presence of blood in the stool and only people in whom blood is found in the stool will be required to undergo a colonoscopy.
The immunological test is not a screening at the individual level, it is what is called a population-based screening. We can have patients with cancer and a negative test and conversely we can have those who have a positive test and who will have a normal colonoscopy because the blood comes from other benign abnormalities.
– It is during the colonoscopy that we see if the patient has intestinal polyps. Are they necessarily warning signs of colorectal cancer?
There are different types of polyps. There are polyps which are benign and which will never degenerate and then there are polyps at risk of degeneration and these, we know that if we remove them we reduce the risk of colorectal cancer. This removal of the polyps is done during the colonoscopy and the interest of this act is precisely both diagnostic and therapeutic.
– Screening is done to identify possible cancer at an early stage so that it can be treated. But how is colorectal cancer treated?
All stages of the strategy are possible. If you do a colonoscopy and a polyp is found with a small cancer, it can be cured by removing the polyp during the colonoscopy. The second step is when we find a cancer that is limited to the colon and there we have recourse to surgery to remove the tumor which will be, depending on the case, more or less followed by chemotherapy. This is how colorectal cancer can be cured.
– How many lives could be saved if the screening objectives were achieved?
The more people who participate in screening, the more the cancer mortality rate will be reduced. The European objective was set at 45% and bridge simulations were carried out: if 100% of the population took part in screening tests, mortality from colorectal cancer would be reduced by 50% and if 50% of people take part, we reduce by 25% and if only 10% participate, we only reduce by 5%. We can clearly see that the more the population participates, the more we reduce mortality from this cancer, but we can clearly see that we are below the recommendations compared to other European countries, which is a real problem.
– Could we better mobilize on this screening with more anxiety-provoking messages?
Maybe, but I don’t know if scaring people gets them to participate or not. This subject could be the subject of a real debate! There is also the problem of these frightening diseases… But things have been tested recently, such as providing treating physicians with a list of their patients who have not been screened so that they can contact them again by trying to motivate them, there have been direct shipments to patients’ homes for screening tests. All this made it possible to increase participation a little bit, but these are operations that require time and money. Perhaps it should above all be remembered that when you have metastatic colorectal cancer, the chances of recovery are extremely limited, that there has been little progress in recent years in terms of increased survival at this stage of the disease. New immunotherapies only concern 4% of colorectal cancers and for the others, chemotherapies only save a few months of survival…
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