Purpose Cancer-related mortality, a leading cause of death worldwide, is often the result of metastatic disease recurrence. Anesthetic techniques have varying effects on innate and cellular immunity, activation of adrenergicinflammatory pathways, and activation of cancerpromoting cellular signaling pathways; these effects may translate into an influence of anesthetic technique on longterm cancer outcomes. To further analyze the effects of propofol (intravenous) and volatile (inhalational gas) anesthesia on cancer recurrence and survival, we undertook a systematic review with meta-analysis. Source Databases were searched up to 14 November 2018. Comparative studies examining the effect of inhalational volatile anesthesia and propofol-based total intravenous anesthesia (TIVA) on cancer outcomes were included. The Newcastle Ottawa Scale (NOS) was used to assess methodological quality and bias. Reported hazard ratios (HRs) were pooled and 95% confidence intervals (CIs) calculated. Principal findings Ten studies were included; six studies examined the effect of anesthetic agent type on recurrencefree survival following breast, esophageal, and non-small cell lung cancer (n = 7,866). The use of TIVA was associated with improved recurrence-free survival in all cancer types (pooled HR, 0.78; 95% CI, 0.65 to 0.94; P \ 0.01). Eight studies (n = 18,778) explored the effect of anesthetic agent type on overall survival, with TIVA use associated with improved overall survival (pooled HR, 0.76; 95% CI, 0.63 to 0.92; P \ 0.01).

Cancer, currently the leading cause of death in the population aged less than 85 years, poses a significant global disease burden and is anticipated to continue to increase in incidence in both developed and developing nations. A substantial proportion of cancers are amenable to surgery, with more than 60% of patients undergoing tumour resection. Up to 80% of patients will receive anaesthesia for diagnostic, therapeutic or palliative intervention. Alarmingly, retrospective studies have implicated surgical stress in disease progression that is predominantly characterised by metastatic disease-the primary cause of cancer-associated mortality. Our understanding of the mechanisms of surgical stress and impact of perioperative interventions is, however, far from complete. Accumulating evidence from preclinical studies suggests that adrenergic-inflammatory pathways may contribute to cancer progression. Importantly, these pathways are amenable to modulation by adapting surgical (e.g. minimally invasive surgery) and anaesthetic technique (e.g. general vs. neuraxial anaesthesia). Disturbingly, drugs used for general anaesthesia (e.g. inhalational vs. intravenous anaesthesia and potentially opioid analgesia) may also affect behaviour of tumour cells and immune cells, suggesting that choice of anaesthetic agent may also be linked to adverse long-term cancer outcomes. Critically, current clinical practice guidelines on the use of anaesthetic techniques, anaesthetic agents and perioperative adjuvants (e.g. anti-inflammatory drugs) during cancer surgery do not take into account their potential effect on cancer outcomes due to a lack of robust prospective data. To help address this gap, we provide an up-to-date review of current clinical evidence supporting or refuting the role of perioperative stress, anaesthetic techniques and anaesthetic agents in cancer progression and review pre-clinical studies that provide insights into biological mechanisms.