Primary tumor location and the prognosis of patients after local treatment of colorectal liver metastases: a systematic review and meta-analysis

Background: Recently numerous studies have reported primary tumor location as a potential prognostic factor after surgery for colorectal liver metastases (CRLM). The aim of this study was to comprehensively review and analyze all the available literature on the impact of primary tumor location in patients after local treatment of CRLM. Methods: Studies examining the association of right- and left-sided colorectal cancer and overall survival (OS) and recurrence free survival (RFS) after local treatment (resection and/or ablation) of CRLM were identified. Random-effects models were used for both clinicopathological and outcome variables. Pooled hazard ratios (HR) with 95% confidence intervals (95% CI) were shown for both OS and RFS. Results: Ten studies (including 11 patient cohorts) were eligible for inclusion, representing 3962 patients. Right-sided tumors (i.e. proximal to the splenic flexure) were observed in 1340 patients (33.8%). Median follow-up ranged from 25 to 137 months. Patients with right-sided tumors had a significantly decreased OS (HR 1.60, 95% CI 1.30–1.98, p < 0.001) and RFS (HR 1.35, 95% CI 1.04–1.77, p = 0.03), when compared to patients with left-sided tumors. Conclusion: This meta-analysis suggests that patients with right-sided primaries suffer from a worse prognosis, compared to patients with left-sided primaries in patients after local treatment of CRLM.