BACKGROUND & AIMS: In 2018, the World Endoscopy Organization (WEO) introduced standardized methods for calculating post-colonoscopy colorectal cancer-3yr rates (PCCRC-3yr). This systematic review aimed to calculate the global PCCRC-3yr according to the WEO methodology, its change over time, and to measure the association between risk factors and PCCRC occurrences. METHODS: We searched 5 databases from inception until January 2024 for PCCRC-3yr studies that strictly adhered to the WEO methodology. The overall pooled PCCRC-3yr was calculated. For risk factors and time-trend analyses, the pooled PCCRC-3yr and odds ratios (ORs) of subgroups were compared. RESULTS: Several studies failed to adhere to the WEO methodology. Eight studies from 4 Western European and 2 Northern American countries were included, totalling 220,106 detected-colorectal cancers (CRCs) and 18,148 PCCRCs between 2002 and 2017. The pooled Western World PCCRC-3yr was 7.5% (95% confidence interval [CI], 6.4%-8.7%). The PCCRC-3yr significantly (P <
.05) decreased from 7.9% (95% CI, 6.6%-9.4%) in 2006 to 6.7% (95% CI, 6.1%-7.3%) in 2012 (OR, 0.79
95% CI, 0.72-0.87). There were significantly higher rates for people with inflammatory bowel disease (PCCRC-3yr, 29.3%
OR, 6.17
95% CI, 4.73-8.06), prior CRC (PCCRC-3yr, 29.8%
OR, 3.03
95% CI, 1.34-4.72), proximal CRC (PCCRC-3yr, 8.6%
OR, 1.51
95% CI, 1.41-1.61), diverticular disease (PCCRC 3-yr, 11.6%
OR, 1.74
95% CI, 1.37-2.10), and female sex (PCCRC-3yr, 7.9%
OR, 1.15
95% CI, 1.11-1.20). CONCLUSION: According to the WEO methodology, the Western World PCCRC-3yr was 7.5%. Reassuringly, this has decreased over time, but further work is required to identify the reasons for PCCRCs, especially in higher-risk groups. We devised a WEO methodology checklist to increase its adoption and standardise the categorization of patients in future PCCRC-3yr studies.