Summary of findings for the main comparison. Epidural anaesthesia in addition to general anaesthesia compared with general anaesthesia alone for patients undergoing primary tumour surgery.

Epidural anaesthesia in addition to general anaesthesia compared with general anaesthesia alone for patients undergoing primary tumour surgery
Patient or population: patients undergoing primary tumour surgery Settings: Intervention: epidural anaesthesia and analgesia in addition to general anaesthesia Comparison: general anaesthesia alone
Outcomes	Illustrative comparative risks* (95% CI)		Relative effect† (95% CI)	Number of participants (studies)	Quality of the evidence (GRADE)
	Assumed risk	Corresponding risk
	General anaesthesia alone (control)	Epidural anaesthesia in addition to general anaesthesia (intervention)
Death from all causes Range of follow‐up timesa: 7.8‐14.8 years (Myles) 8.3‐10.75 years (Christopherson)	Study population		HR 1.03 (0.86 to 1.24)	647 (3 studies)	⊕⊕⊝⊝ lowb,c
	805 per 1000a	815 per 1000 (755 to 868)
Tumour progression or death from all causes Range of follow‐up times: 7.8‐14.8 yearsd	Study population		HR 0.88 (0.56 to 1.38)	535 (2 studies)	⊕⊝⊝⊝ very lowb,c,e
	944 per 1000d	921 per 1000 (802 to 981)
Tumour progression Median follow‐up: 4.5 yearsf	Study population		HR 1.50 (1 to 2.25)	545 (2 studies)	⊕⊝⊝⊝ very lowb,c,h
	360 per 1000g	488 per 1000 (360 to 634)
*The basis for the assumed risk (e.g. median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: Confidence interval; HR: Hazard ratio.
GRADE Working Group grades of evidence. High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate.

HR = hazard ratio, defined as intervention/control.

^†HR < 1 denotes advantage for the intervention group, HR > 1 denotes advantage for the control group.

^aThe assumed risk and the range of follow‐up times are based on data reported by Myles and Christophersen. Data on absolute events per group were not reported by Binczak.
 ^bSerious indirectness (‐1): Regional anaesthesia techniques are a surrogate for reduced or absent immunosuppression mediated by opioids and volatile anaesthetics, both of which are not controlled for in the included studies.
 ^cSerious imprecision (‐1): Combined sample sizes are deemed too small to show an effect.
 ^dThe assumed risk and the range of follow‐up times are based on data from Myles only. Data on absolute risk for tumour progression and death from all causes are not reported by Binczak.
 ^eSerious inconsistency (‐1): substantial unexplained heterogeneity.
 ^fThe median follow‐up time is based on data from Tsui.
 ^gThe assumed risk is based on data from Tsui only. Data on the absolute risk for TTP are not reported by Myles.
 ^hSerious risk of bias (‐1): 1 study with unclear risk of selective reporting and other bias.