As usual, several provocative additions to the colorectal cancer literature were published last month, but I will review only one today: the NordICC trial. This trial evaluated the use of screening colonoscopy to reduce the incidence of colorectal cancer, death from colorectal cancer, and all-cause mortality.
We have long accepted that colonoscopy is the gold standard for detection of colorectal cancer, but until the publication of this study there has never been a prospective, randomized controlled clinical trial to evaluate the efficacy of the test. Nearly 85,000 men and women from Nordic nations were randomly assigned to receive an invitation for either screening colonoscopy or usual care (ie, no colonoscopy). In the intention-to-screen analysis, colonoscopy reduced the risk for colorectal cancer over a period of 10 years by 18% (relative risk [RR] 0.82; 95% CI 0.70-0.93). However, the reduction in risk for death from colorectal cancer failed to reach statistical significance (RR 0.90; 95% CI 0.64-1.16).
These results were especially disappointing because sigmoidoscopy, a test that evaluates only the rectum and left colon, has been shown in multiple studies to reduce risk for colorectal cancer death and all-cause mortality. It is difficult for me to think of a biologically plausible explanation for colonoscopy to be less effective than sigmoidoscopy in the prevention of cause-specific and all-cause death. However, potential explanations are hidden in the study data. Most glaringly, only 42% of the colonoscopy invitees received a colonoscopy as compared with a much larger percentage of patients (58%-87%) in the sigmoidoscopy trials. While this might be an important real-world data point, it is far less than the estimated 60% of patients in the United States who adhere to the recommendation for screening colonoscopy from ages 45 to 55. Additionally, the study had only 10 years of follow-up. It is possible that this is just not long enough for the benefits of screening colonoscopy to be fully realized. Finally, 29% of endoscopists had an adenoma detection below the recommended threshold of 25%, suggesting that poor colonoscopic technique may have played a role in the limited efficacy of colonoscopy found in the study.
Regardless of what we think of these results, the study was generally well designed and, therefore, very important. Studies like this give us critical information that we, as a nation, need to determine how best to allot our limited healthcare resources. While this study does not change my perception of the efficacy of colonoscopy, it makes me think twice about its societal utility.