Evidence-Based Guideline: The USPSTF recommends screening for colorectal cancer in adults 50 to 75 years of age

Questions In asymptomatic adults, what are the effectiveness, diagnostic accuracy, and harms of screening tests for colorectal cancer (CRC)? What are the US Preventive Services Task Force (USPSTF) recommendations for screening? * Review scope Included studies evaluated screening tests (colonoscopy; flexible sigmoidoscopy [FS]; computed tomographic colonography; stool screening tests, including guaiac fecal occult blood [FOBT], fecal immunochemical, and stool-based DNA; and methylated SEPT9 DNA blood test) for CRC in asymptomatic adults 40 years of age who were either unselected or at average risk. Outcomes included CRC mortality, diagnostic test characteristics for detecting colorectal cancer or adenomas, and harms. Review methods MEDLINE, PubMed, and Cochrane Central Register of Controlled Trials (2008 to 2014); reference lists from systematic reviews, including the previous 2008 USPSTF review; trial registries; and high-impact journals and article alerts (2015 to Feb 2016) were searched for English-language, fair- or good-quality (based on prespecified criteria), randomized, controlled trials (RCTs) and other controlled trials, observational studies, and diagnostic accuracy studies. Experts were consulted. 25 included studies evaluated test effectiveness, 33 diagnostic accuracy, and 98 harms. Main results The main results of the review are in the Table. Based on the review results and a modeling study, the USPSTF recommends CRC screening in adults 50 to 75 years of age (grade A recommendation based on evidence with high certainty of substantial net benefit) and in selected adults 76 to 85 years of age based on individual circumstances (grade C recommendation based on evidence with at least moderate certainty of small net benefit). * Conclusion The US Preventive Services Task Force recommends screening for colorectal cancer in adults 50 to 75 years of age. Selected findings for colorectal cancer screening tests in asymptomatic adults* Questions Outcomes Test/studies (n) Findings Effectiveness Colorectal cancer mortality Flexible sigmoidoscopy (1 or 2 rounds)/4 RCTs (458002) Reduced events vs no screening: 33 vs 45 events/100000 person-y, pooled IRR 0.73 (95% CI 0.66 to 0.82) at 11- to 12-y Biennial guaiac fecal occult blood test (2 to 9 rounds)/5 RCTs (404396) Reduced events vs no screening: RRR 9% (CI 2 to 16) to 22% (CI 7 to 35) at 11- to 30-y Diagnostic accuracy Detecting adenomas 6 mm CTC with bowel preparation/7 studies (5328) Per-person sensitivity/specificity with colonoscopy as the reference standard (single, repeat if indicated, or segmental unblinding): 73%/not reported to 98%/91% Detecting advanced adenomas FIT: OC-Light/3 studies (25924); OC FIT-CHEK/5 studies (12794) Sensitivity/specificity with colonoscopy as reference standard: OC-Light 28%/94% to 40%/91%; OC FIT-CHEK 22%/97% to 44%/90% Detecting colorectal cancer FIT: OC-Light/3 studies (25924); OC FIT-CHEK/5 studies (12794) Sensitivity/specificity with colonoscopy as reference standard: OC-Light {79%/93%} to 88%/91%; OC FIT-CHEK 73%/96% to 100%/94% Harms Perforations Colonoscopy/26 studies (3414108) 3.6 events/10000 procedures (CI 2.4 to 5.4) Flexible sigmoidoscopy/16 studies (329698) 0.74 events/10000 procedures (CI 0.4 to 1.4) Major bleeding Colonoscopy/22 studies (3347101) 8.2 events/10000 procedures (CI 5.0 to 14) Flexible sigmoidoscopy/10 studies (137987) 1.8 events/10000 procedures (CI 0.7 to 4.4) *CTC = computed tomographic colonography; FIT = fecal immunochemical test; IRR = incidence rate ratio; RCT = randomized controlled trial; other abbreviations defined in Glossary. Weighted screening event rate for flexible sigmoidoscopy calculated from no screening event rate x IRR. Provided by author. Commentary Both the USPSTF and recent Canadian (1) 2016 guidelines call for CRC screening. However, the Canadian guidelines specifically recommend FOBT or FS, the only 2 methods for which RCTs have shown reductions in both CRC incidence and mortality, and recommend against colonoscopy because of the absence of RCTs (1). The USPSTF recommends screening using any available method. An argument for this position is that any accepted screening method would be better than no screening. Lin and colleagues found that FS is an effective screening method; therefore, colonoscopy probably will be as well. Because colonoscopy has higher associated costs and complication rates, it has to be better than FS by a wide enough margin to justify these downsides. It is unfortunate that none of the ongoing RCTs of colonoscopy compare it with FS because an indirect comparison suggested that FS may be better than FOBT (2). Further, the claim by the USPSTF that CRC screening saves life-years is based on a model that begins with that assumption. Neither FOBT nor FS has been shown to affect all-cause mortality (3), and as CRC mortality often occurs in persons >75 years of age, CRC screening may simply substitute one cause of death for another. If no life-years are saved, CRC screening would not be economically justifiable as the cost per life-year saved would be infinite.