The association between anaesthetic technique and cancer specific survival following surgical resection of non-small cell lung cancer

Abstract

Introduction Due to the biological effects of anaesthetics on the immune system, it has been hypothesised that use of volatile anaesthetics during lung cancer surgery may negatively affect cancer outcomes compared to total intravenous anaesthetics. This study sought to investigate the relationship between anaesthetic choice and lung cancer outcome; the primary outcome was time to cancer specific mortality, with the secondary outcome of time to mortality of any cause. The effect of dose of volatile anaesthetic received was also explored in relation to cancer specific survival. Methods This is a retrospective cohort study of patients who underwent elective open lung resection for non-small cell lung cancer between January 2010 and December 2014. Surgical records were combined with both information from the Scottish Cancer Registry and continuously recorded, electronically measured anaesthetic data. Kaplan-Meier survival curves were drawn for cancer specific and overall survival and tested for significance using Log-rank testing. Factors influencing survival were analysed using univariate and multivariate Cox Proportional Hazards Ratios. Exposure to volatile anaesthetic was quantified by determining the area under the end tidal expired anaesthetic agent vs time curve. This was adjusted for anaesthetic type using minimum alveolar concentration (MAC), to give MAC-hours which were plotted against vital status then assessed using logistic regression. Results Final analysis included 746 patients, 342 received total intravenous anaesthetic and 404 were exposed to volatile agents, with mean time to follow up of 3.65 (1.2-6.1) years. Log rank testing did not demonstrate significant differences in survival between volatile and total intravenous anaesthetics in terms of cancer specific (p = 0.80) or overall survival (p = 0.74). Anaesthetic type was not found to be a significant predictor for cancer specific or overall survival in univariate or multivariate Cox analysis (p = 0.81 for cancer specific survival and p = 0.94 for overall survival). Logistic regression used to assess dose-response was not significant for cancer specific survival (p = 0.054). No significance was found in univariate or multivariate Cox analysis for cancer specific survival based on logistic regression results. Discussion This study found no significant relationship between anaesthetic technique and long term non-small cell lung cancer survival. This contradicts a large body of retrospective work suggesting a survival benefit in patients receiving total intravenous anaesthetic for cancer surgery, but is in keeping with the findings of Oh et al (1) who also demonstrated no effect in 362 patients undergoing surgery resection for non-small cell lung cancer. Ultimately a randomised controlled trial is required in this area.