Impact of general or regional anaesthesia on recurrence of colorectal cancer after surgery: Systematic review

Background and Aims: Studies have suggested that anaesthetic agents have modulatory effects on the immune system, leading to cancer recurrence. The association between colorectal cancer (CRC) recurrence and anaesthesia is still unclear. Therefore, this systematic review aimed to determine the association between the recurrence of CRC after surgery and anaesthesia. Methods: A database search of PubMed, Cochrane, Embase, and Scopus was performed for articles on the recurrence of CRC after surgeries under general anaesthesia (GA) and regional anaesthesia (RA), published between January 2002 and January 2023. Qualitative and risk-of-bias assessment of retrospective studies was performed using the Newcastle–Ottawa scale (NOS). Synthesis Without Meta-analysis guidelines were used to report data synthesis. The primary outcome was cancer recurrence, and the secondary outcomes were disease-free survival (DFS) and overall survival. The standardised metric to represent data synthesis was the median hazard ratio (HR). Evidence quality was rated as per GRADE pro-GDT. Results: A total of six retrospective cohorts were identified through the literature search for inclusion. The risk of bias was low in all studies and was rated good quality as per the NOS. The pooled risk ratio for cancer recurrence in the two studies was 1.04, 95% confidence interval 0.98–1.10 ( P = 0.20). The median HR for cancer recurrence was 0.895. DFS was not statistically significant with GA or RA, with a median HR of 1.06. Conclusion: No conclusive association was found between regional anaesthesia and colorectal cancer recurrence. However, due to a lack of studies reporting cancer recurrence and less data for comparison and different intervention groups, a conclusive association cannot be made.