Abstract: We included four studies with a total of 746 participants. All studies included adult patients undergoing surgery for primary tumour resection. Two studies enrolled male and female participants undergoing major abdominal surgery for cancer. One study enrolled male participants undergoing surgery for prostate cancer, and one study male participants undergoing surgery for colon cancer. Follow-up time ranged from nine to 17 years. All four studies compared general anaesthesia alone versus general anaesthesia combined with epidural anaesthesia and analgesia. All four studies are secondary data analyses of previously conducted prospective randomized controlled trials. Of the four included studies, only three contributed to the outcome of overall survival, and two each to the outcomes of progression-free survival and time to tumour progression. In our meta-analysis, we could not find an advantage for either study group for the outcomes of overall survival (hazard ratio (HR) 1.03, 95% confidence interval (CI) 0.86 to 1.24) and progression-free survival (HR 0.88, 95% CI 0.56 to 1.38). For progression-free survival, the level of inconsistency was high. Pooled data for time to tumour progression showed a slightly favourable outcome for the control group (general anaesthesia alone) compared with the intervention group (epidural and general anaesthesia) (HR 1.50, 95% CI 1.00 to 2.25). Quality of evidence was graded low for overall survival and very low for progression-free survival and time to tumour progression. The outcome of overall survival was downgraded for serious imprecision and serious indirectness. The outcomes of progression-free survival and time to tumour progression were also downgraded for serious inconsistency and serious risk of bias, respectively. Reporting of adverse events was sparse, and data could not be analysed. Currently, evidence for the benefit of regional anaesthesia techniques on tumour recurrence is inadequate. An encouraging number of prospective randomized controlled trials are ongoing, and it is hoped that their results, when reported, will add evidence for this topic in the near future.

Plain-language summary: We found four studies with a total of 746 adult men and women undergoing abdominal surgery for removal of cancer. All studies were reanalyses of previously conducted trials, which means that none of the included studies was actually designed to investigate tumour recurrence. All patients underwent primary cancer surgery, which means that surgery on cancer metastases was not included. A total of 354 participants received general anaesthesia and 392 participants received a general anaesthesia along with an epidural anaesthesia. Epidural anaesthesia is a certain type of regional anaesthesia by which a numbing medication is injected continuously via a catheter into the epidural space. The epidural space serves as the outermost surrounding of the spinal cord. Numbing medication injected into the epidural space causes certain parts of the belly area to go numb and be insensitive to pain. Study participants were followed for at least 7.8 years after they had undergone cancer surgery. We did not find a benefit for either study group on cancer recurrence or survival. Because of incomplete reporting and the low number of reported adverse events, we cannot estimate possible differences in adverse effects between the different anaesthesia techniques used. The quality of the evidence for outcomes was graded low for overall survival and very low for progression-free survival and time to tumour progression. The main limitations of the evidence we identified were that the results could have been influenced by the background treatments given to people who participated in the trials.