The object of this study is to evaluate the superiority of aprepitant therapy with a 5HT3-receptor antagonist, dexamethasone and aprepitant compared to standard therapy with a 5HT3-receptor antagonist and dexamethasone for prevention of nausea and vomiting in first course chemotherapy.

Inclusion Criteria:

• Age: ≥20 years old
• Sex: Not specified
• Patients with colon/rectal cancer who first underwent FOLFOX, XELOX or SOX regimen including oxaliplatin at ≥85 mg/m2 (naive patient), or those who had already started chemotherapy and had nausea of Grade 2 or higher in the last course or an earlier course (non-naive patient).
• Stage: not specified (neoadjuvant/adjuvant chemotherapy, advanced or recurrent type are allowed)
• Combination of molecular targeted therapy: allowable
• Written informed consent for participation in the study.

Exclusion Criteria:

• Severe liver or kidney disease
• Nausea/vomiting within 24 hr prior to chemotherapy.
• Treatment with antiemetics within 24 hr prior to chemotherapy.
• Presence of factors causing nausea/vomiting other than chemotherapy (e.g. brain tumor, gastrointestinal obstruction, active peptic ulcer disease, brain metastasis)
• Presence of a disease precluding 3-day administration of dexamethasone (e.g. uncontrollable diabetes)
• Pregnant or lactating women, women who plan to become pregnant.
• Current treatment with pimozide.
• Any patient judged to be inappropriate for the study by the investigator.