Background: Olanzapine is an inexpensive and durable agent for the treatment of chemotherapy-induced nausea and vomiting and is also superior to neurokinin-1 receptor antagonists in the control of nausea. This study aimed to investigate the efficacy and safety of a low dose of 5 mg olanzapine plus granisetron and dexamethasone for treatment of carboplatin (CBDCA)-induced nausea and vomiting in patients with thoracic malignancies. Materials and Methods: We conducted a prospective, open-label, single-arm, multicenter, phase II trial in four centers in Japan. Registered patients were scheduled to receive area under the curve (AUC) ≥5 mg/mL per minute of CBDCA and had never received moderately to highly emetogenic chemotherapy. Patients received olanzapine 5 mg/day orally after supper for 4 days, in combination with granisetron and dexamethasone. Primary endpoint was complete response (CR; no emesis and no use of rescue medication) rate during the overall phase (0–120 hours). Results: Between February 2018 and June 2020, 51 patients were enrolled, and 50 patients were evaluated. The CR rates in the overall (0–120 hours), acute (0–24 hours), and delayed phases (24–120 hours) were 94.0%, 100%, and 94.0%, respectively. No grade 3 or higher adverse effects of olanzapine were observed. Conclusion: Prophylactic antiemetic therapy with a low dose of 5 mg olanzapine plus granisetron and dexamethasone showed durable efficacy with an acceptable safety profile. This three-drug combination appears to be a reasonable treatment approach in patients with thoracic malignancies receiving an AUC ≥5 mg/mL per minute of CBDCA-based regimen. Clinical trial identification number: UMIN000031267. Implications for Practice: The results of this phase II trial indicated that the prophylactic administration of low-dose of 5 mg olanzapine combined with granisetron and dexamethasone has promising activity with acceptable safety profile in patients with thoracic malignancy receiving high-dose carboplatin chemotherapy.
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