Opioid-Free Anesthesia and Postoperative Outcomes in Cancer Surgery: A Systematic Review

SIMPLE SUMMARY: As a significant knowledge gap exists on the effect of opioid-free anesthesia on outcomes of cancer patients receiving surgery, we conducted a systematic review to assess any differences between opioid-free and opioid-based anesthesia. Few studies were included, as the main body of the existing literature in the specific population of oncologic surgery does not reflect high quality standards and displays strong heterogeneity in methodology. Despite encouraging suggestions from the few studies regarding the benefits of opioid-free approaches on the immediate perioperative outcome, more trials are required to accept or reject the superiority of opioid-free anesthesia in patients receiving surgery for cancers. ABSTRACT: Background: Surgery is an essential component of the treatment of solid tumors, but the perioperative course can be complicated by different factors (including anesthesia). Opioid-free anesthesia (OFA) may mitigate adverse outcomes of opioid-based anesthesia (OBA), but major questions remain on the actual impact in terms of analgesia and the improvement of surgical outcomes. To address this issue, we present a systematic review to evaluate the efficacy of OFA compared to OBA in the specific subset of cancer patients undergoing surgery. Methods: following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA), we searched MEDLINE, Embase and the Cochrane CENTRAL Library to include randomized controlled trials (RCTs) on adults undergoing oncological surgery, comparing OFA and OBA up to March 2022. Additional papers were added from the reference lists of identified sources. Papers were manually reviewed by two independent authors to ascertain eligibility and subsequent inclusion in qualitative analysis. Results: only two studies were eligible according to inclusion criteria. It was not possible to perform any meta-analysis. The two studies included patients undergoing prostate and gynecologic surgery on 177 patients, with significant heterogeneity in the outcomes. Conclusions: randomized controlled trial specifically addressed to cancer patients are lacking. A knowledge gap exists, neither confirming nor rejecting the capacity of OFA to improve early postoperative outcomes in cancer surgery. Long-term consequences on specific oncological outcomes are far from being elucidated. We expect a growing body of literature in the coming years. Further studies are required with homogeneous methodology and endpoints.