The Relationship between Distal Hyperplastic Polyp and Proximal Colorectal Neoplasia: A Systematic Review and Meta-Analysis
Flexible sigmoidoscopy (FS) and colonoscopy are recommended as endoscopic test choices for colorectal cancer (CRC) screening. FS is now gaining popularity in some European countries and Asia Pacific regions since it can be performed by primary care professionals and it will be more suitable for resource limited areas. Although the use of FS for CRC screening has been proved effective by several randomized control trials, the main drawback of FS includes its inability to examine the proximal colon. Referral of distal adenoma(s) detected by FS for further colonoscopy followup has been widely accepted as a standard practice. However, whether screening participants with distal hyperplastic polyps (HPs) detected by FS should be followed by subsequent colonoscopy is controversial. We evaluated the association between distal HPs and proximal neoplasia (PN)/advanced proximal neoplasia (APN) in asymptomatic, average-risk patients.
We searched Ovid Medline, EMBASE and the Cochrane Library from inception to 31 July 2016, and included all screening studies that examined the relationship between different distal findings and PN/APN. Data were independently extracted by two reviewers with disagreements resolved by a third reviewer. We pooled absolute risks and odds ratios with a random effects meta-analysis. Four subgroup analyses were performed according to study characteristics. Heterogeneity was examined by the I2 statistics. The present systematic review and meta-analysis adhered to the PRISMA statement.
Twenty eight eligible studies were finally identified, including a total of 104,961 subjects (Figure 1). Overall, the prevalence of colorectal neoplasia was 25.0%; advanced colorectal neoplasia 4.9%; PN 13.2% and APN 2.2%. When compared with normal distal findings, distal HP was not associated with PN (OR=1.16, 95% CI 0.89-1.51, p=0.14, I2=40%) or APN (OR=1.09, 95% CI 0.87-1.36, p=0.39, I2=5%) (Figure 2), whilst subjects with distal non-advanced or advanced adenoma had higher odds of PN and APN. Higher odds of PN/APN were observed for more severe distal lesions. Weaker association between distal and proximal findings was noticed in studies with higher quality, larger sample size, population-based design and better endoscopy quality control measures. There was no significant heterogeneity when the associations between distal HP and PN (I2=40%, p=0.28) /APN (I2=5%, p=0.39) were examined. The Egger’s regression tests showed that publication bias did not exist (all p > 0.05).
The presence of distal HP is not associated with PN/APN in asymptomatic screening population. Our findings do not support routine colonoscopy workup for subjects with distal HPs detected by sigmoidoscopy, and provided concrete evidence in support of the US Preventive Services Task Force Recommendation Statements published in 2016. We anticipate that this clinical implication has a substantial potential to reduce unnecessary colonoscopy procedures, complications and healthcare costs for primary care physicians, particularly in regions where colonoscopic capacity may be limited.