Systematic review of the efficacy of antiemetics in the treatment of nausea in patients with far-advanced cancer

Objectives. To systematically review studies of antiemetics used in the treatment of nausea in patients with far-advanced cancer. Data sources. Randomized controlled trials (RCT) and uncontrolled studies identified by electronic and hand searching. Review methods. Identified studies were appraised for quality and effect size. Results. Of 21 studies included, 2 were systematic reviews, 7 were RCT and 12 were uncontrolled studies or case series. Differences in interventions and outcomes amongst the RCT precluded any quantitative data synthesis and all seven studies were prone to bias. Whereas uncontrolled studies indicated a high response rate to standard regimens (75-93% for both nausea and vomiting), RCT showed much lower response rates to these agents (23-36% for nausea, 18-52% for vomiting). The two methods of antiemetic choice (choice based either on the inferred mechanism or empirical) were equally effective. There is reasonably strong evidence for the use of metoclopramide in cancer-associated dyspepsia and steroids in malignant bowel obstruction. There was conflicting evidence about the efficacy of serotonin antagonists compared with standard treatments (e.g. metoclopramide, dopamine antagonists and dexamethasone). There was little or no evidence of the efficacy of some commonly used and seemingly effective drugs such as haloperidol, cyclizine, and methotrimeprazine. Conclusion. Evidence supporting the existing consensus-based guidelines for management of nausea and vomiting in advanced cancer is sparse. Current approaches to treatment based on the neuropharmacology of the emetic pathway may be inappropriate in this setting. Well-designed studies of the impact of "standard" management and novel agents on nausea and vomiting in palliative populations are needed.