Canadian Journal of Gastroenterology and Hepatology

Review Article

Colorectal Cancer Screening in Average Risk Populations: Evidence Summary

Table 5

GRADE evidence profile—FS versus no screening.
Quality assessmentNumber of patientsEffectQualityImportance
Number of studiesDesignRisk of biasInconsistencyIndirectnessImprecisionOther considerationsFS (cases/person-years)No screening (cases/person-years)Relative
(95% CI)		Absolute
(cases/person-years)
CRC mortality (follow-up: 6–12 years)
4Randomized trials Not serious Not serious Not serious Not serious Not serious576/1,902,184 (0.03%)1321/3,114,546 (0.04%)RR 0.72 
(0.65–0.80) 		119 fewer per 1,000,000 (from 85 fewer to 148 fewer)⨁⨁⨁⨁ 
High		 Critical
Control (gFOBT + FS) = 0.06%168 fewer per 1,000,000 (from 120 fewer to 210 fewer)
Complications from tests (from Holme  et al. 2013 [10])1
5Randomized trialsNot seriousNot seriousNot seriousNot seriousNot serious N/A2  ⨁⨁⨁⨁ 
High		Critical
All-cause mortality (follow-up: 6–12 years)
4Randomized trials Not serious Not serious Not serious Not serious Not serious19,525/1,902,184 (1.0%)32,903/3,114,546 (1.1%)RR 0.97 
(0.96–0.99) 		317 fewer per 1,000,000 (from 106 fewer to 423 fewer)⨁⨁⨁⨁  
High		 Important
Control (gFOBT + FS) = 1.85%555 fewer per 1,000,000 (from 185 fewer to 740 fewer)
CRC incidence (follow-up: 6–12 years)
4Randomized trials Not serious Not serious Not serious Not serious Not serious2218/1,860,990 (0.1%)4579/3,067,081 (0.1%)RR 0.78 
(0.74–0.83) 		328 fewer per 1,000,000 (from 254 fewer to 388 fewer)⨁⨁⨁⨁ 
High		Important
Control (gFOBT + FS) = 0.16%352 fewer per 1,000,000 (from 272 fewer to 416 fewer)
CI: confidence interval; CRC: colorectal cancer; FS: flexible sigmoidoscopy; gFOBT: guaiac fecal occult blood test; GRADE: Grading of Recommendations, Assessment, Development and Evaluations; RR: relative risk; N/A: not applicable.
In order to have comparable control rates across all gFOBT and FS trials, the control rates for the no screening groups in the gFOBT and FS trials were combined and calculated from the total number of cases across all gFOBT and FS trials over the total number of person-years across all gFOBT and FS trials.
1Major complication rate included bleeding, perforation, or death within 30 days of screening, follow-up colonoscopy, or surgery.
2Holme et al. 2013 [10] reported a major complication rate of 0.08%.