Seventeen trials were included in the review with 8,740 patients (sample size range 46 to 1,933). Randomisation, blinding, description of drop-outs and sample size calculation were deemed adequate in nearly all trials. Only three trials used an intention-to-treat analysis, but drop-out rates were generally low.
Overall, neurokinin-1 receptor antagonists increased the rate of patients' complete response (OR 0.51, 95% CI 0.46 to 0.57; 13 trials; Ι²=12%) with a significant decrease in the frequency of vomiting, nausea and use of rescue medication. Neurokinin-1 receptor antagonists increased the rate of complete response in the acute phase (OR 0.56, 95% CI 0.48 to 065; 15 trials; Ι²=22%) and in the delayed phase (OR 0.48, 95% CI 0.42 to 0.56; 15 trials; Ι²=47%).
A benefit of neurokinin-1 receptor antagonists was seen for both highly emetogenic chemotherapy (OR 0.46, 95% CI 0.40 to 0.53) and moderately emetogenic chemotherapy (OR 0.59, 95% CI 0.51 to 0.67). The benefit was slightly greater if ondansetron was not used in the control group (OR 0.47, 95% CI 0.41 to 0.53) than if it was (OR 0.64, 95% CI 0.54 to 0.76). There was no evidence of differences for any other subgroups.
There was some evidence that neurokinin-1 receptor antagonists significantly increased the incidence of severe infections, hiccups, and asthenia or fatigue, but reduced the incidence of constipation. There were no statistically significant differences between groups for other adverse events.
There was no evidence of publication bias.