Nausea and vomiting caused by chemotherapy are considered by patients as the main side effects of cancer treatment, which affect the quality of treatment and life.At present, NCCN guidelines have recommended three or four drug regimens for highly emetic chemotherapy (HEC) to prevent vomiting, all containing dexamethasone.However, its side effects such as moderate to severe insomnia, hyperglycemia, dyspepsia, upper abdominal discomfort, irritability, increased appetite, weight gain and acne are gathering increasing concerns.For certain patients, the use of dexamethasone should be avoided.Analysis shows that olanzapine can replace the effect of dexamethasone.Hence, the investigators initiated this prospective, multi-center, phase III study to validate the dexamethasone-free protocol: removing dexamethasone from a three drug regimen containing olanzapine, dexamethasone, and 5-HT3RA.

Inclusion Criteria:

1. Patients 18 years of age or older with malignant disease；
2. Life expectancy ≥ 3 months;
3. Scheduled to receive highly emetogenic chemotherapy；
4. Had a European Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2

Exclusion Criteria:

1. There are contraindications to chemotherapy(Absolute number of neutrophils ≤ 1,500/uL, hemoglobin ≤ 90g/L, platelet count ≤ 10000/uL, serum creatinine level ≥ 2.0mg/dl (177 μmol/L), ALT and AST ≥ 2.5 times the upper normal limit, bilirubin ≥ 1.5 times the upper normal limit);
2. History of central nervous system disease (e.g., brain metastases or a seizure disorder);
3. Severe cognitive impairment；
4. Treatment with another antipsychotic agent such as risperidone, quetiapine, clozapine, a phenothiazine, or a butyrophenone within 30 days before enrollment or plans for such treatment during the study period;
5. Concurrent use of pharyngeal or abdominal radiotherapy;
6. Concurrent use of quinolone antibiotics;
7. Concurrent use of Amifostine;
8. Chronic alcoholism;
9. Known hypersensitivity to olanzapine;
10. Know arrhythmia, uncontrolled congestive heart failure or acute myocardial infarction within 6 months;
11. Known uncontrolled diabetes mellitus;
12. Vomiting or retching 24 hours before chemotherapy;
13. Use of anti-emesis drugs 48 hours before chemotherapy;
14. Patients who require medication with dexamethasone for pretreatment.