Chemotherapy-induced nausea and vomiting is a common side effect of cancer treatments, and dexamethasone offers a clear advantage over placebo for protection against chemotherapy-induced emesis in both acute and delayed phases. 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. Several clinical trials have shown that olanzapine plays an important role in treating delayed, refractory, breakthrough nausea and vomiting. Its side effects mainly include sedation and weight gaining. At present, the NCCN guidelines have recommended olanzapine-containing three-drug regimen for Highly Emetogenic Chemotherapy (HEC) and moderate emetic chemotherapy (MEC) to prevent vomiting, but its data in the Chinese population is limited. Hence, we initiated this prospective, multi-center, phase III study to validate the dexamethasone-free protocol: applying olanzapine to prevent CINV instead of dexamethasone.

Inclusion Criteria (Patients are eligible to be included in the study only if they meet all of the following criteria):

1. Cancer patients, age ≥ 18 years and ≤75 years, ECOG score 0-2 points, receiving cisplatin-containing doublet chemotherapy such as cisplatin + gemcitabine / albumin paclitaxel / etoposide /fluorouracil / irinotecan / temozolomide as first line treatment;
2. Life expectancy ≥ 3 months;
3. Leucocytes≥3,000/uL;
4. AST≤2.5 × upper limit of normal;
5. Bilirubin ≤1.5 × upper limit of normal;
6. Serum creatinine ≤ 1.5 × upper limit of normal.

Exclusion Criteria (Patients will be excluded if any of the following criteria is met):

1. History of CNS disease, such as brain metastases or epilepsy;
2. Use of other antipsychotic drugs (such as risperidone, quetiapine, clozapine, phenothiazine, or butyrophenone, or such treatment is under scheduling during the study) within 30 days before enrollment; long-term use of phenothiazine as an antipsychotic agent;
3. Concurrent use of pharyngeal or abdominal radiotherapy;
4. Concurrent use of quinolone antibiotics;
5. Chronic alcoholism;
6. Known hypersensitivity to olanzapine;
7. Know arrhythmia, uncontrolled congestive heart failure or acute myocardial infarction within 6 months;
8. Known uncontrolled diabetes mellitus;
9. Vomiting or retching 24 hours before chemotherapy;
10. Use of anti-emesis drugs 48 hours before chemotherapy;
11. Concurrent use of amifostine;
12. Concurrent use of corticosteroids and the only anti-allergic choice is corticosteroids