Ondanstron Weekly vs Every 3 Weeks for Prevention of Nausea and Vomiting Induced by Chemotherapy Combined With PD-1 Blockade

Inclusion Criteria: 1. Age ≥ 18 years, no gender limit; 2. Pathologically or cytologically confirmed malignant solid tumors; 3. Scheduled to receive cisplatin-based chemotherapy combined with PD-1 blockade； 4. TPS \> 1 %(PD-1); 5. Adequate hematological function (leucocyte count ≥ 4000/μL \[to convert to ×109/L,multiply by 0.001\], hemoglobin ≥ 9.00 g/dL \[to convert to grams per liter, multiply by 10\], and platelet count ≥ 100 × 103/μL \[to convert to ×109/L, multiply by 1\]); 6. Hepatic function (alanine aminotransferase and aspartate aminotransferase ≤ 2.0 times the upper limit of the reference ranges), and renal function (creatinine clearance ≥ 60 mL/min/1.73 m2 \[to convert to millimeters per second per meter-squared, multiply by 0.0167\])； 7. Estimated survival time \> 6 months； 8. ECOG 0-1 points； 9. Participants being informed and signed written consents. Exclusion Criteria: 1. Nausea or vomiting caused by reasons except for chemotherapy and PD-1 blockade; 2. Participants with other malignant tumors history previously; 3. Inability to read, comprehend, and finish questionnaires; 4. Allergic to the drugs included in this study. 5. Administered drugs with antiemetic activity within the 24 hours before receiving the first dose of study medication.