Efficacy of Olanzapine 5 mg versus 10 mg for the Prophylaxis of Chemotherapy-Induced Nausea and Vomiting in Patients Receiving High Emetic Risk Chemotherapy without Neurokinin-1 Receptor Antagonist

OBJECTIVE: To compare the efficacy and safety of two different dosage levels of olanzapine for the prevention of chemotherapy-induced nausea and vomiting (CINV) in patients receiving high emetic risk chemotherapy. METHODS: This study was a randomized, double-blind, controlled trial designed to show non-inferiority in the efficacy of olanzapine 5 mg compared to 10 mg in patients treated with high dose cisplatin or doxorubicin/cyclophosphamide. Non-inferiority was defined as a lower margin of the 95% confidence interval (95% CI) that not lower than the margin set at -25%. RESULT: A total of 140 patients were randomized to 5 mg group (n=70) or 10 mg group (n=70) of olanzapine. The complete response (CR) rate in the overall phase of olanzapine 5 and 10 mg was 58.6% v 62.9% (95%CI: -20.4, 11.8). The CR rate comparison between olanzapine 5 and 10 mg was 81.4% v 74.3% (95%CI: -6-6, 20.8) and 66.7% v 76.1% (95%CI: -23.5, 6.3) for the acute and delayed phase, respectively. No nausea rates in acute, delayed and overall phase were 70.0% v 68.6% (95%CI: -13.8, 16.6), 45.7% v 48.6% (95%CI: -19.4, 13.6) and 43.5% v 47.9% (95%CI: -19.2, 13.6). The rate of adverse events (AE) including somnolence were not different between the 5 and 10 mg groups. CONCLUSION: The two dosage levels of olanzapine were not different in terms of the efficacy and AE in the prophylaxis of CINV.