Adherence to Colonoscopy in Cascade Screening of Colorectal Cancer: A Systematic Review and Meta-Analysis

Background: Adherence-to-colonoscopy in cascade screening of colorectal cancer (CRC) is crucial to the effectiveness of screening, but it has not been systematically evaluated. We aimed to evaluate the colonoscopy adherence among average-risk populations globally. Methods: We searched Pubmed, Embase, Web of Science, and Cochrane Library for observational and experimental studies published in English up to December 31, 2018 and reporting the colonoscopy adherence following positive initial screening. We calculated pooled adherence with its 95% confidence intervals (CIs) using a random-effects meta-analysis. Subgroup and mixed-effects meta-regression analysis were performed to evaluate heterogeneous factors for adherence. Findings: Of 9,772 articles identified, 191 (313 studies) were included in the systematic review. The pooled adherence-to-colonoscopy was 81·6% (95% CI: 79·6-83·4), with the estimates varying substantially by continents, CRC incidence, GDP per capita, recruitment method, screening round and type of initial test. Type of initial test was the most modifiable heterogeneous factor for adherence across studies (Q=53·00, P <0·001). The adherence level was the highest when FS (89·0%, 83·5-92·9) was used as an initial test, followed by gFOBT (84·0%, 81·3-86·5), quantitative (82·7%, 80·8-84·5) or qualitative (72·8%, 65·6-79·0) FIT and risk assessment (70·7%, 38·8-90·2). The pooled estimate of adherence was positively associated with the specificity and PPV of initial tests, but negatively with the sensitivity and positivity rate. Interpretation: Colonoscopy adherence is suboptimal overall and differs by study-level characteristics of the populations and programmes under screening. The use of initial screening test with higher specificity and PPV may enhance adherence-to-colonoscopy follow-up. Funding Statement: This study was supported by the Local High Level University Construction Project of Shanghai and the Health Commission of the Pudong New Area of Shanghai (PW2019A-5). Declaration of Interests: The authors declare no potential conflicts of interest.