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

Aim: 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.

Method: 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. I was used to assess between-study heterogeneity. Quality appraisal was undertaken with the Newcastle-Ottawa Score.

Results: 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, I  = 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, I  = 85.6%, n = 3). There was no association with overall survival (HR = 1.04, 95% CI: 0.94-1.15, I  = 43.7%, n = 7). Significant heterogeneity was present but subgroup analysis did not account for this.

Conclusion: 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.