Aprepitant Without Steroid in Preventing Chemotherapy-induced Nausea and Vomiting in Patients With Colorectal Cancer

Inclusion Criteria: * Diagnosis of colorectal cancer * No prior chemotherapy and scheduled to receive FOLFOX chemotherapy (oxaliplatin,leucovorin and 5-fluorouracil) * Age ≥18 years * Eastern Cooperative Oncology Group (ECOG) Performance Status 0, 1 or 2 * Laboratory index: Hemoglobin ≥ 90 g/L (No blood transfusion within 14 days), Absolute Neutrophil Count ≥ 1.5×10\^9/L, Platelet Count ≥ 75×10\^9/L, Serum Bilirubin ≤ 1.5×ULN, ALT and AST ≤ 3.0×ULN (without liver metastases), ALT and AST ≤ 5.0×ULN (with liver metastases), Serum Creatinine ≤ 1×ULN, Endogenous Creatinine Clearance\>60ml/min * Be able to read, understand and complete the questionnaire and diary * Be able to understand the study procedures and sign informed consent. Exclusion Criteria: * Treatment with any other study medicine within 4 weeks before enrollment. * Nausea or vomiting ≤ 24 hours prior to registration * Ongoing emesis due to obstruction of digestive tract * Concurrent use of olanzapine, phenothiazine or amifostine * Female with pregnancy or lactation * Severe cognitive compromise * Known history of CNS disease (e.g. brain metastases, seizure disorder) * Concurrent abdominal radiotherapy * Chronic alcoholism * Known hypersensitivity to aprepitant, tropisetron, or dexamethasone. * Known cardiac arrhythmia, uncontrolled congestive heart failure or acute myocardial infarction within the previous six months. * History of uncontrolled diabetes mellitus * Serious or uncontroled infection * Known active HIV, viral hepatitis or tuberculosis infections