Arm A: Ondansetron 0.15 mg/kg (max 16 mg) IV or PO every 8 hours for at least 3 days, but no longer than 5 days; dexamethasone 0.2mg/kg (max 10 mg) IV or PO daily for at least 3 days, but no longer than 5 days; and aprepitant 3 mg/kg (max 125 mg) PO on day 1, and aprepitant 2 mg/kg (max 80 mg) PO on days 2 and 3 during the first investigational antiemetic cycle. During the next investigational antiemetic cycle, members of this arm will be crossed-over into the placebo arm, where the aprepitant will be replaced by placebo and the dexamethasone dose will be increased to 0.4 mg/kg (max 20 mg) daily.

Arm B: Ondansetron 0.15 mg/kg (max 16 mg) IV or PO every 8 hours for at least 3 days, but no more than 5 days; dexamethasone 0.4 mg/kg (max 20 mg) IV or PO daily for at least 3 days, but no more than 5 days; and a PO placebo for 3 days during the first investigational antiemetic cycle. During the second cycle, members this group will be crossed-over to the experimental arm, where the placebo will be replaced by aprepitant and the dexamethasone will be decreased by 50%.

Ondansetron 0.15 mg/kg (max 16 mg) IV or PO every 8 hours for at least 3 days, but no longer than 5 days; dexamethasone 0.2mg/kg (max 10 mg) IV or PO daily for at least 3 days, but no longer than 5 days; and aprepitant 3 mg/kg (max 125 mg) PO on day 1, and aprepitant 2 mg/kg (max 80 mg) PO on days 2 and 3 during the first investigational antiemetic cycle. During the next investigational antiemetic cycle, members of this arm will be crossed-over into the placebo arm, where the aprepitant will be replaced by placebo and the dexamethasone dose will be increased to 0.4 mg/kg (max 20 mg) daily.

• Percentage of study subjects who demonstrate a complete response, defined as no episodes of emesis and no use of rescue medications during the investigational antiemetic cycles.

• The total episodes of emesis within 7 days of the first chemotherapy administration of each cycle.
• The total number of administrations of rescue medications given for breakthrough nausea or vomiting.

• A modified, 5-day recall version of the Functional Living Index-Emesis (FLIE) questionnaire

• A modified version of the Baxter Animated Retching Faces (BARF) scale, administered daily.

• Occurrence of adverse events as per the NCI Common Terminology Criteria for Adverse Events (CTCAE) v.4.0. These will be reported spontaneously or on inquiry by the investigator/study nurse, and continuously monitored throughout the trial.
• Weekly complete blood count (CBC) for 3 weeks after each investigational antiemetic cycle.
• Weekly complete metabolic profile (CMP) for 3 weeks after each investigational antiemetic cycle.