A new guideline suggested, based on a modeling study and low-quality evidence, that screening for colorectal cancer may not be necessary in low-risk individuals ages 50 to 79 years.
The guideline was developed by the BMJ Rapid Recommendations project, a collaborative effort from the MAGIC research and innovation program and The BMJ. For individuals with an estimated 15-year colorectal cancer risk below 3%, the guideline authors suggested no screening (weak recommendation). For individuals with an estimated 15-year risk above 3%, they suggested screening with one of four options: fecal immunochemical test (FIT) every year, FIT every two years, a single sigmoidoscopy, or a single colonoscopy (weak recommendation). The recommendations were published by The BMJ on Oct. 2.
The recommendations were based in part on a microsimulation modelling study using MIcrosimulation SCreening ANalysis-Colon (MISCAN-Colon) among Norwegian men and women ages 50 to 79 years with varying 15-year colorectal cancer risk (1% to 7%). Over 15 years of follow-up, the model showed that screening individuals ages 50 to 79 years who were at 3% risk of colorectal cancer with annual FIT or single colonoscopy reduced colorectal cancer mortality by 6 per 1,000 individuals compared to no screening. Single sigmoidoscopy and biennial FIT reduced mortality by 5 per 1,000 individuals. Colonoscopy, sigmoidoscopy, and annual FIT reduced colorectal cancer incidence by 10, 8, and 4 per 1,000 individuals, respectively. Estimated incidence reduction for biennial FIT was 1 per 1,000 individuals.
Harms were similar across the four screening strategies. Serious harms were estimated to be between 3 per 1,000 (biennial FIT) and 5 per 1,000 individuals (colonoscopy). Harms increased with older age. The results quantify screening benefits, harms, and burdens on an individual level and support shared decision making about screening, the authors wrote. Although the panel inferred that most informed individuals with a 15-year risk of 3% or higher are likely to choose screening and most with a risk below 3% are likely to decline screening, optimal care will require shared decision making, given varying values and preferences.
“For example, based on a certain colorectal cancer risk threshold, some low risk individuals may conclude that the undesirable consequences of screening outweigh the desirable consequences,” they wrote. “Evaluating the modelling results, we predicted that lifetime follow-up of screened individuals resulted in different estimates of screening effectiveness compared with 15 year follow-up. This additional finding encourages researchers to continue the follow-up in their randomised cohorts to evaluate longer term benefits of screening.”
An accompanying editorial noted that “Fully informed decision making is destined to bring radical changes in the way cancer screening is introduced, as the priority is to ensure that eligible adults have received appropriate, balanced information on screening. One consequence of a shift from maximising participation to informed choice could be lower participation in screening programmes.”