Systematic review and meta‐analysis: Associations between metabolic syndrome and colorectal neoplasia outcomes

Metabolic syndrome (MetS) is a cluster of factors including obesity, hypertension, diabetes, hypercholesterolemia and hyperlipidaemia. It has been associated with an increased risk of colorectal neoplasia. This systematic review and meta-analysis assessed the association between MetS and (i) recurrence of adenomas or occurrence of CRC in patients with prior adenomas, and (ii) survival in patients with CRC.MEDLINE, Embase, Scopus and Web of Science were searched up to 22 November 2019. Two authors independently conducted title and abstract screening; full text of eligible studies was evaluated. Where ≥3 studies reported effect measures for a specific outcome, meta-analysis using random effects model was conducted. I2 was used to assess between-study heterogeneity. Quality appraisal was undertaken with the Newcastle-Ottawa Score.The search identified 1,764 articles, 55 underwent full text screening, resulting in a total of 15 eligible studies. Five studies reported on metachronous neoplasia, with differing outcomes precluded a meta-analysis. No consistent relationship between MetS and metachronous neoplasia was found. Ten studies reported on survival outcomes. MetS was associated with poorer CRC-specific survival (HR = 1.8, 95% CI: 1.04-3.12, I2 = 92.7%, n = 3). Progression-free survival was also worse but this did not reach statistical significance (HR = 1.12, 95% CI: 0.89-1.42, I2 = 85.6%, n = 3). There was no association with overall survival (HR = 1.04, 95% CI: 0.94-1.15, I2 = 43.7%, n = 7). Significant heterogeneity was present but subgroup analysis did not account for this.MetS is associated with poorer CRC-specific survival, but evidence is inconsistent on metachronous neoplasia. Further research is warranted to better understand the impact of MetS on the adenoma-carcinoma pathway.