Disappointing Colorectal Cancer Screening Results with Colonoscopy
A randomised study of northern European data shows that colonoscopy screening reduces the risk of colorectal cancer by 18%, much smaller than experts previously assumed. The results of the study appear in the New England Journal of Medicine.
Colonoscopy may not even perform better than screening with faecal tests, said Louise Emilsson, docent at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, and national Swedish principal investigator of the study.
Prior to the publication of this study, experts assumed that screening with colonoscopy had significantly better effect than screening with faecal tests. Faecal tests are used in colorectal cancer screening programs in many countries, and other countries have introduced screening with colonoscopy based on the fact that researchers via observational and modelling studies estimated that up to nine out of ten cases of colorectal cancer could be prevented with a colonoscopy screening. With faecal tests, similar models has estimated the effect to be two to three out of ten.
In the NordICC study, the researchers investigated the extent to which colonoscopy screening actually prevents colorectal cancer. Overall, 1.2% of those randomised to no screening were diagnosed with colon cancer during ten years, compared to 0.98% in those offered screening.
This translates to an 18% reduced risk of colorectal cancer among the participants who were offered colonoscopy screening. Furthermore, 455 colonoscopies were required to prevent one single case of colorectal cancer. Colonoscopy is fairly invasive and costly procedure, involving preparation, bowel prep with laxatives, and a 30-45 minute examination of the bowel with a camera inserted via the rectum. The figure of 455 procedures to prevent one case of cancer is certainly disappointing, Louise Emilsson concluded.
Colorectal cancer mortality was also found to be lower than expected in the NordICC study. Only three in a thousand died of the disease within ten years, regardless of whether they were offered screening or not, and thus, there was no significant difference between the groups in terms of mortality. The low mortality rate is however encouraging and likely caused by significantly improved treatment options over the past ten years.
Source: Karolinska Institutet
