The objectives of the study are: 1) Primary: Assess CINV efficacy of Aprepitant in combination with Ondansetron vs. Ondansetron alone in preventing acute and delayed CINV (Complete Control (CC): days 1-7) in brain tumor patients during adjuvant temozolomide therapy; and 2) Secondary: To assess the efficacy of Aprepitant in combination with Ondansetron vs Ondansetron alone in preventing acute CINV in brain tumor patients during the acute period (first 24 hours) of receiving adjuvant temozolomide therapy; 3)Secondary: To assess the efficacy of Aprepitant in combination with Ondansetron vs. Ondansetron alone in preventing delayed CINV (days 2-7); 4) Secondary: To assess the safety and tolerability of Aprepitant administered concomitantly with Ondansetron; 5) Exploratory: To assess the time to treatment failure of Ondansetron treatment with and without Aprepitant; 6) Exploratory: To explore the effects of age, gender, chemotherapy history, and concomitant glucocorticoid on the efficacy of Ondansetron treatment with and without Aprepitant; 7) Exploratory: To explore the impact of Aprepitant on quality of life and daily function.