Inclusion Criteria:

1. Sign a written informed consent form and voluntarily enroll in this study;

2. Be at least 18 years of age; gender is not a restriction;

3. Be a patient scheduled to receive treatment with Trastuzumab Rezetecan;

4. Have an ECOG performance status score of 0-2;

5. No ascites or pleural effusion requiring drainage;

6. No gastrointestinal obstruction, such as pyloric stenosis or intestinal obstruction;

7. Expected survival of ≥12 weeks;

8. Good organ and bone marrow function, defined as follows:

   Hematologic System (No blood transfusions or treatment with hematopoietic growth factors within the past 14 days)

   • Absolute Neutrophil Count (ANC) ≥ 1.5×10⁹/L
   • Platelets (PLT) ≥ 100×10⁹/L
   • Hemoglobin (Hb) ≥ 90 g/L Liver Function
   • Total Bilirubin (TBIL) ≤ 1.5×ULN (For patients with Gilbert's syndrome: ≤ 3×ULN)
   • Alanine Aminotransferase (ALT) ≤ 2.5×ULN (Patients with liver metastases: ≤ 5×ULN)
   • Aspartate Aminotransferase (AST) ≤ 2.5×ULN (Patients with liver metastases: ≤ 5×ULN)
   • Albumin (ALB) ≥ 30 g/L Renal Function
   • Creatinine (Cr) ≤ 1.5×ULN
   • Creatinine Clearance (Ccr)
   • (Calculated only when creatinine > 1.5×ULN) Endogenous creatinine clearance ≥ 50 mL/min (Cockcroft-Gault formula) Cardiac Function
   • 12-lead electrocardiogram No severe arrhythmias, and a mean Fridericia-corrected QT interval (QTc) of <450 ms (males) or <470 ms (females)
   • Echocardiogram Left ventricular ejection fraction (LVEF) ≥ 50%

9. Agree to cooperate in completing daily nausea and vomiting logs and scale assessments;

10. Understand the nature of this study; the patient and/or legal guardian voluntarily agree to participate in this trial and sign the informed consent form.

Exclusion Criteria:

1. Allergy to the study drug or its excipients;
2. Known contraindications to NK-1 receptor antagonists, 5-HT3 receptor antagonists, or dexamethasone;
3. Nausea or vomiting at the time of enrollment requiring treatment with antiemetics;
4. Use of medications with antiemetic effects within 2 days prior to the first dose;
5. Initiation of potent opioid analgesics within 48 hours prior to enrollment (adjustment of the dose of medications already in use is permitted);
6. Presence of conditions affecting the assessment of vomiting, such as gastrointestinal obstruction, gastroparesis, or intestinal obstruction;
7. Patients who are difficult to enroll due to clinically diagnosed psychiatric disorders;
8. Localized or active systemic infections requiring treatment;
9. Pregnant or breastfeeding women, as well as patients of childbearing age who refuse to use appropriate contraceptive measures during the course of this trial;
10. Patients who have participated in other clinical trials within 30 days prior to the first dose of the study drug (patients who failed screening for other clinical trials may be enrolled in this study);
11. Patients with other factors deemed by the investigator to be unsuitable for participation in this study, such as any physiological or psychological conditions that may increase study risks, affect patient adherence to the protocol, or interfere with the patient's ability to complete the trial.