The Immunomodulatory Effect of Various Anaesthetic Practices in Patients Undergoing Gastric or Colon Cancer Surgery: A Systematic Review and Meta-Analysis of Randomized Clinical Trials.

Background: Gastric and colorectal carcinomas are associated with increased mortality and an increasing incidence worldwide, while surgical resection remains the primary approach for managing these conditions. Emerging evidence suggests that the immunosuppression induced by the chosen anaesthesia approach, during the perioperative period, can have a significant impact on the immune system and consequently the prognosis of these patients.

Aim: This systematic review aims to comprehensively summarize the existing literature on the effects of different anaesthesia techniques on immune system responses, focusing on cellular immunity in patients undergoing the surgical removal of gastric or colorectal carcinomas. There is no meta-analysis investigating anaesthesia's impact on immune responses in gastric and colorectal cancer surgery. Anaesthesia is a key perioperative factor, yet its significance in this area has not been thoroughly investigated. The clinical question of how the anaesthetic technique choice affects the immune system and prognosis remains unresolved.

Methods: Major electronic databases were searched up to February 2023 to May 2023 for relevant randomized controlled trials (RCTs). The study protocol has been registered with Prospero (CRD42023441383).

Results: Six RCTs met the selection criteria. Among these, three RCTs investigated the effects of volatile-based anaesthesia versus total intravenous anaesthesia (TIVA), while the other three RCTs compared general anaesthesia alone to the combination of general anaesthesia with epidural anaesthesia. According to our analysis, there were no significant differences between TIVA and volatile-based anaesthesia, in terms of primary and secondary endpoints. The combination of general anaesthesia with epidural analgesia had a positive impact on NK cell counts (SMD 0.61, 95% CI 0.28 to 0.94, I 0.0% at 24 and 72 h after the operation), as well as on CD4 cells (SMD 0.59, CI 95% 0.26 to 0.93, I 0.0%). However, the CD3 cell count, CD4/CD8 ratio, neutrophil-to-lymphocyte ratio (NLR), IL-6 and TNF-α levels remained unaffected.

Conclusions: The combination of epidural analgesia and general anaesthesia can potentially improve, postoperatively, the NK cell count and CD4 cell levels in gastric or colon surgery patients. However, the specific impact of TIVA or volatile-based anaesthesia remains uncertain. To gain a better understanding of the immunomodulatory effects of anaesthesia, in this particular group of cancer patients, further well-designed trials are required.