Screening for Colorectal Cancer
Updated Evidence Report and Systematic Review for the US Preventive Services Task Force
Published in: JAMA, v. 315, no. 23, June 21, 2016, p. 2576-2594
Posted on RAND.org on June 27, 2016
- What is the current evidence for the effectiveness, diagnostic accuracy, and harms of different modalities used to screen for colorectal cancer?
- What is the current evidence for screening test accuracy for detection of asymptomatic colorectal cancer and adenomas?
- What is the current evidence related to serious harms that could result from participating in screening? Do potential harms vary by subpopulations such as age?
IMPORTANCE: Colorectal cancer (CRC) remains a significant cause of morbidity and mortality in the United States. OBJECTIVE: To systematically review the effectiveness, diagnostic accuracy, and harms of screening for CRC. DATA SOURCES: Searches of MEDLINE, PubMed, and the Cochrane Central Register of Controlled Trials for relevant studies published from January 1, 2008, through December 31, 2014, with surveillance through February 23, 2016. STUDY SELECTION: English-language studies conducted in asymptomatic populations at general risk of CRC. DATA EXTRACTION AND SYNTHESIS: Two reviewers independently appraised the articles and extracted relevant study data from fair- or good-quality studies. Random-effects meta-analyses were conducted. MAIN OUTCOMES AND MEASURES: Colorectal cancer incidence and mortality, test accuracy in detecting CRC or adenomas, and serious adverse events. RESULTS: Four pragmatic randomized clinical trials (RCTs) evaluating 1-time or 2-time flexible sigmoidoscopy (n = 458 002) were associated with decreased CRC-specific mortality compared with no screening (incidence rate ratio, 0.73; 95% CI, 0.66-0.82). Five RCTs with multiple rounds of biennial screening with guaiac-based fecal occult blood testing (n = 419 966) showed reduced CRC-specific mortality (relative risk [RR], 0.91; 95% CI, 0.84-0.98, at 19.5 years to RR, 0.78; 95% CI, 0.65-0.93, at 30 years). Seven studies of computed tomographic colonography (CTC) with bowel preparation demonstrated per-person sensitivity and specificity to detect adenomas 6 mm and larger comparable with colonoscopy (sensitivity from 73% [95% CI, 58%-84%] to 98% [95% CI, 91%-100%]; specificity from 89% [95% CI, 84%-93%] to 91% [95% CI, 88%-93%]); variability and imprecision may be due to differences in study designs or CTC protocols. Sensitivity of colonoscopy to detect adenomas 6 mm or larger ranged from 75% (95% CI, 63%-84%) to 93% (95% CI, 88%-96%). On the basis of a single stool specimen, the most commonly evaluated families of fecal immunochemical tests (FITs) demonstrated good sensitivity (range, 73%-88%) and specificity (range, 90%-96%). One study (n = 9989) found that FIT plus stool DNA test had better sensitivity in detecting CRC than FIT alone (92%) but lower specificity (84%). Serious adverse events from colonoscopy in asymptomatic persons included perforations (4/10 000 procedures, 95% CI, 2-5 in 10 000) and major bleeds (8/10 000 procedures, 95% CI, 5-14 in 10 000). Computed tomographic colonography may have harms resulting from low-dose ionizing radiation exposure or identification of extracolonic findings. CONCLUSIONS AND RELEVANCE: Colonoscopy, flexible sigmoidoscopy, CTC, and stool tests have differing levels of evidence to support their use, ability to detect cancer and precursor lesions, and risk of serious adverse events in average-risk adults. Although CRC screening has a large body of supporting evidence, additional research is still needed.
- Only two screening modalities (flexible sigmoidoscopy and guiaiac-based fecal occult blood tests) have been shown to reduce colorectal cancer mortality.
- Neither screening with colonoscopy nor CT colonography (CTC) have been shown to reduce colorectal cancer mortality, but several studies have examined the sensitivity and specificity of these structural tests to detect both adenomas, which may transition to cancer, and asymptomatic colorectal cancers.
- Estimates of the accuracy of fecal immunochemical tests (FIT) vary widely. The FDA-approved OC-Light and OC FIT-CHEK tests are the best studied and have better operating characteristics (sensitivity and specificity) than guaiac-based tests. Evidence-based reasoning supports the use of these FIT tests for screening.
Although there is a large body of evidence related to colorectal cancer screening, gaps in knowledge remain and further research is needed (a) to estimate the effect of CRC screening programs using a range of newer modalities on cancer mortality, (b) to better determine the accuracy of stool screening tests to detect both CRC or advanced adenoma, and (c) to better understand the risks of serious adverse outcomes from colonoscopy in average-risk adults.