A double-blind randomized phase II dose-finding study of olanzapine 10 mg or 5 mg for the prophylaxis of emesis induced by highly emetogenic cisplatin-based chemotherapy.

PURPOSE: The aim of this phase II study was to evaluate the efficacy and safety of two doses (10 and 5 mg) of olanzapine in combination with standard antiemetic treatment (aprepitant, palonosetron, and dexamethasone) for patients receiving highly emetogenic chemotherapy (HEC).

METHODS: A multi-institutional, double-blind, randomized phase II, dose-finding study of olanzapine was performed in patients with a malignant solid tumor who were receiving HEC with cisplatin (≥ 50 mg/m2 ). Patients were randomly assigned either olanzapine 10 or 5 mg orally on days 1-4, combined with standard antiemetic treatment. The primary endpoint was a complete response (CR; no emesis and no use of rescue medications) in the delayed phase (24-120 h after the start of cisplatin treatment).

RESULTS: 153 patients were randomized to the 10 mg group (n = 76) or the 5 mg group (n = 77). The CR rate in the delayed phase was 77.6% (80% CI: 70.3-83.8, P = 0.01) in the 10 mg group and 85.7% (80% CI: 79.2-90.7, P < 0.001) in the 5 mg group (P value for H 0 : complete response rate ≤ 65%). The most common adverse event was somnolence, which had an incidence of 53.3 and 45.5% in the 10 and 5 mg olanzapine groups, respectively.

CONCLUSIONS: Both doses of 10 and 5 mg olanzapine provided a significant improvement in delayed emesis. A dose of 5 mg olanzapine was determined as the recommended dose for a further phase III study based on higher CR and lower somnolence rates.

CLINICAL TRIAL INFORMATION: UMIN000014214.