Colonoscopy is one of the screening tests for colorectal cancer, one of the most common cancers. And yet, a recently published randomized study concludes that it does not save lives. What is it really?
Going through a colonoscopy is an unpleasant and dreaded moment for patients. The intervention consists of exploring the rectum, small intestine and large intestine with a camera in search of polyps that may become cancerous in the coming years. It is an integral part of the screening strategy for colorectal cancer, one of the most common among men and women over 50 years of age.
To date, no randomized study has concluded that colonoscopy effectively reduces colorectal cancer mortality, and by extension, that this screening test is without risk to health and does not increase the risk of mortality from any cause. A study published in The NEJM, held in Norway, Poland, and Sweden, tackled this problem head-on. The conclusions go against what was supposed: this test does not reduce mortality from colon cancer.
Colonoscopy and incidence of colorectal cancer
The study protocol replicates a colorectal cancer screening program. Among the 80,000 participants in the three countries, some are invited to undergo a colonoscopy (28,000 people), of which 42% will actually pass the exam. Colon cancer incidence and deaths are monitored for 10 years and compared with 56,000 people who were not invited and did not have a colonoscopy. The scientists made sure that the latter did not pass one outside of the clinical trial.
At the beginning of the ten years of follow-up, the scientists first observed an increased risk of colorectal cancer in patients who were asked to take the test, an expected trend since the test reveals the presence of cancer. But after six years of follow-up, the risk of colorectal cancer in people who don’t get screened goes up. In total, the risk of colorectal cancer is 0.98 in screened patients and 1.20 in unscreened people.
No mortality benefit
The same follow-up was done for the risk of death from colorectal cancer or from any other cause. In this case, there is no benefit for the patients evaluated. After ten years of follow-up, the risk of death related to colon cancer is 0.28% (72 recorded deaths) for people screened by colonoscopy and 0.31% for people not screened. In the screened group, the scientists listed 11.03% of all-cause deaths in the “screened” group and 11.04% in the “unscreened” group. Therefore, the study shows that colonoscopy has no benefit on colorectal cancer mortality.
Colonoscopy is not the only possible screening test to prevent colorectal cancer, sigmoidoscopy stands out. This less invasive test only looks at the rectum, sigmoid colon, and left colon, unlike a colonoscopy that goes further up the digestive system. Sigmoidoscopy requires fewer medical resources to perform, but has been gradually replaced by colonoscopy. However, scientists note: These results suggest that colonoscopy may not be much more effective in reducing colorectal cancer risk than sigmoidoscopy. »
In France, colon cancer screening (stool analysis and colonoscopy in case of abnormality) is recommended for all people aged 50 to 74 years and is reimbursed by health insurance.