Nanocrystalline Megestrol for Managing Chemotherapy-Induced Nausea and Vomiting

Inclusion Criteria: * Aged ≥ 18 years, regardless of gender; * Histologically or cytologically confirmed malignant solid tumor; * No prior exposure to any chemotherapy drugs (antitumor drugs not used for cancer treatment, or intravesical instillation therapy for bladder cancer is not considered as chemotherapy); * Initially planned to receive single-day moderate to high emetogenic chemotherapy (MEC/HEC) drugs; * Expected survival period ≥ 6 months; * Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1; * Good organ function, meeting the following criteria: 1. Neutrophil count ≥ 1.5×10⁹/L; 2. Hemoglobin ≥ 90 g/L; 3. Platelet count ≥ 100×10⁹/L; 4. Total bilirubin ≤ 1.5×ULN; 5. In patients without known liver metastasis, aspartate aminotransferase ≤ 2.5×ULN and/or alanine aminotransferase ≤ 2.5×ULN (for patients with liver metastasis, it can be relaxed to ≤ 5×ULN); 6. Serum creatinine ≤ 1.5×ULN or creatinine clearance rate ≥ 50 ml/min; 7. Electrocardiogram: QTc ≤ 450 ms (male), QTc ≤ 470 ms (female); 8. Echocardiogram: LVEF (left ventricular ejection fraction) ≥ 50%; * Female subjects of childbearing potential and male subjects whose partners are female of childbearing potential need to use a highly effective contraceptive method from the time of signing the informed consent form until 6 months after the last dose (see Appendix VII); female subjects of childbearing potential must have a negative blood pregnancy test within 72 hours before randomization; and must be non-lactating; * Clearly understand and voluntarily participate in the study, and sign the informed consent form in person. Exclusion Criteria: * Having received abdominal (including the diaphragmatic plane and below) or pelvic radiotherapy within 7 days before enrollment, or planning to receive such radiotherapy within days 1 to 8 of treatment; * Planning to receive other moderate to high emetogenic chemotherapy drugs within days 2 to 8 after the first day of chemotherapy; * Planning to receive chemotherapy regimens including conventional paclitaxel (using castor oil as solvent); * Having taken drugs with potential antiemetic effects within 2 days before enrollment: 5-HT3 receptor antagonists (e.g., ondansetron, etc.), phenothiazines (e.g., prochlorperazine), butyrophenones (e.g., haloperidol), benzamides (e.g., metoclopramide), domperidone, cannabinoids, traditional Chinese medicines with potential antiemetic effects, scopolamine, cyclizine, etc.; * Having started treatment with benzodiazepines or opioids within 2 days before enrollment (except for triazolam, temazepam or midazolam taken alone daily); * Subjects who started using morphine within 7 days before enrollment (except those taking a stable dose); * Having received systemic corticosteroid therapy (including but not limited to dexamethasone, hydrocortisone, methylprednisolone or prednisolone) or sedative antihistamines (such as diphenhydramine) within 7 days before enrollment (Note: single use of steroids to prevent contrast agent allergy and local or inhaled administration are allowed); * Having used palonosetron within 14 days before enrollment; * Having used NK-1 receptor antagonists within 28 days before enrollment; * Having used specific CYP3A4 substrates (terfenadine, cisapride, astemizole) or CYP3A4 inhibitors (such as ritonavir, clarithromycin, ketoconazole or itraconazole, diltiazem, etc.) within 7 days before enrollment, and having used strong CYP3A4 inducers (such as phenobarbital, rifampicin, phenytoin and carbamazepine, etc.) or specific CYP2D6 substrates (thioridazine, pimozide) within 28 days before enrollment; * Having vomiting and/or retching, nausea within 24 hours before enrollment; * Subjects with symptomatic brain metastasis or any symptoms suggesting brain metastasis or intracranial hypertension; * Accompanied by poorly controlled serous cavity effusions, including pleural effusion, ascites, pericardial effusion (those controlled after treatment and stable for ≥ 2 weeks can be included); * Having severe cardiovascular diseases within 3 months before enrollment, including but not limited to acute myocardial infarction, unstable angina pectoris, significant valvular or pericardial diseases, history of ventricular tachycardia, symptomatic chronic heart failure (New York Heart Association \[NYHA\] class II to IV), history of severe cardiac conduction abnormalities (such as torsades de pointes); * Having poorly controlled hypertension before enrollment (systolic blood pressure ≥ 160 mmHg and/or diastolic blood pressure ≥ 100 mmHg at two consecutive resting measurements); * Complicated with active hepatitis B (HBV DNA ≥ 2000 IU/mL or 10⁴ copies/mL), active hepatitis C (HCV-Ab positive, and HCV-RNA ≥ upper limit of normal), acquired immunodeficiency syndrome (AIDS) or positive HIV test, positive syphilis test; * Complicated with concomitant diseases that cannot take dexamethasone, such as active infection (e.g., pneumonia) or any uncontrolled diseases (e.g., diabetic ketoacidosis, gastrointestinal obstruction, etc.); * Known contraindications to NK-1 receptor antagonists, 5-HT3 receptor antagonists or dexamethasone; history of thromboembolic diseases within the past 6 months; * Having participated in other clinical trials within 30 days before enrollment (based on the use of study drugs); * Subjects considered by the researcher to be unsuitable for participating in this study due to other conditions.