Breakthrough chemotherapy-induced vomiting (CIV) is defined as CIV occurring after adequate antiemetic prophylaxis. Olanzapine is recommended for the treatment of breakthrough CIV in children, without adequate evidence. We conducted an open-label, single-center, phase 3 randomized controlled trial comparing the safety and efficacy of olanzapine and metoclopramide for treating breakthrough CIV.

Children aged 5-18 years who developed breakthrough CIV after receiving highly emetogenic chemotherapy were randomly assigned to the control(placebo) or olanzapine arm. The primary objective of the study was to compare the complete response (CR) rates between patients receiving olanzapine or placebo for treating breakthrough CIV during 72 hours after the administration of the study drug. Secondary objectives were to compare CR rates for nausea and toxicities between the two arms.

Inclusion Criteria:

- The major inclusion criteria were children aged 5 to 18 years at the time of study entry with documented cancer; receiving NK-1 inhibitor (aprepitant/fosaprepitant) and 5HT-3 antagonist (ondansetron) and/or dexamethasone as prophylactic antiemetics for CINV due to MEC or HEC; minimum body weight of 10 kg; development of breakthrough vomiting after starting prophylactic antiemetics; Lansky performance scale of above 50 (for patients aged 10 years or less) or Eastern Cooperative Oncology Group performance scale less than 3 and normal electrocardiogram (ECG) before the initiation of the prophylactic antiemetics.

Exclusion Criteria:

• Children with history of allergy to olanzapine or metoclopramide; patient with renal failure, congestive heart failure, or any uncontrolled disease except for malignancy; serum creatinine more than upper limit of normal (ULN) for age; serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) four times the ULN for age and serum bilirubin 1.5 times ULN for age; patient with history of central nervous system disease including brain metastasis, seizure disorder, or psychosis; patients on treatment with other antipsychotic agents such as risperidone, quetiapine, clozapine, or phenothiazine.

Patients were randomized to one of the prespecified two arms (arm A: olanzapine or arm B: placebo) if they developed breakthrough vomiting. The department of biostatistics and cancer registry at the institute assisted in the random allocation of the patients. Randomization was performed by generating random number tables through customized computer program or the proposed total number of cases in the study, and the randomization codes were kept in sequentially numbered sealed envelopes. The envelopes were kept in the pediatric ward and opened when a patient was identified for randomization. A document was then prepared giving the allocation of all the subjects to the two arms in chronological order.