This study is Phase 2 pharmacokinetic (PK) and pharmacodynamic (PD) dose-finding study of oral netupitant administered concomitantly with oral palonosetron in pediatric cancer patients for the prevention of nausea and vomiting associated with emetogenic chemotherapy. Two different netupitant dosages will be tested in patients aged from 3 months to < 18 years: 1.33 mg/kg up to a maximum of 100 mg, and 4 mg/kg up to a maximum of 300 mg. All netupitant doses in all age classes will be concomitantly administered with palonosetron 20 μg/kg (up to a maximum dose of 1.5 mg) which is the IV palonosetron dose approved by USA FDA for the pediatric population. The primary objective is to investigate the PK/PD relationship between netupitant exposure (AUC, Cmax) and antiemetic efficacy (CR in delayed phase) after a single oral netupitant administration, concomitantly with oral palonosetron in pediatric cancer patients receiving Moderately Emetogenic Chemotherapy (MEC) or Highly Emetogenic Chemotherapy (HEC) cycles. Efficacy parameter to be used in the correlation is the proportion of patients with Complete Response (CR i.e., no emetic episodes and no rescue medication) during (> 24-120 h after the start of chemotherapy on Day 1).