Efficacy and Safety of Opioids in Treating Cancer-Related Dyspnea: A Systematic Review and Meta-Analysis Based on Randomized Controlled Trials

Background Dyspnea is one of the most distressing symptoms encountered by advanced cancer patients. In this study, we aimed to evaluate the role of opioids in the management of cancer-related dyspnea. Methods A systematic review and meta-analysis based on Randomized Controlled Trials was conducted in the databases PUBMED, EMBASE, and Cochrane Central Register of Controlled Trials testing the effect of opioids in relieving cancer-related dyspnea. Subgroup and sensitivity analyses were performed to evaluate various types of opioids in dyspnea management and stabilization of the study respectively. Results Eleven RCTs fulfilled the eligibility criteria and had a total of 290 participants. Nine of these studies were included in meta-analyses. Compared with control, opioid therapy showed a small positive effect in dyspnea, SMD-0.82 (95%CI = −1.54 to -0.10) and Borg score, WMD-0.95 (95%CI = −1.83 to -0.06); Opioid therapy did not increase the risk of somnolence, OR0.93 (95%CI = 0.34 to 2.58), whereas a negative effect on respiratory rate was observed,WMD-1.89 (95%CI = −3.36 to -0.43); Also, there was no evidence to suggest improved performance of the 6MWT test, WMD6.49 (95%CI = −34.23 to 47.21), or the level of peripheral oxygen saturation, WMD0.33 (95%CI = −0.59 to 1.24) after opioid therapy. Subgroup analysis yielded a small positive effect for morphine on dyspnea, SMD-0.78 (95%CI = −1.45 to −0.10), whereas fentanyl showed no improvement in dyspnea, SMD-0.44 (95%CI = −0.89 to 0.02). Sensitivity analysis showed no changes in the direction of effect when any one study was excluded from the meta-analyses. Conclusions Our systematic review and meta-analysis indicated low quality evidence for a small positive effect of opioids in cancer-related dyspnea. Evidence for safety is insufficient as comprehensive adverse events were not adequately reported in studies.