A Study on Nausea and Vomiting Caused by T-DXd in Breast Cancer Patients

Inclusion Criteria: 1. The patient is at least 18 years of age; 2. The patient has a histologically or cytologically confirmed diagnosis of breast cancer; 3. The patient is receiving full-dose trastuzumab deruxtecan (T-DXd) monoclonal antibody therapy for the first time; 4. The patient has an Eastern Cooperative Oncology Group (ECOG) performance status score of 2 or lower; 5. The patient voluntarily agrees to comply fully with the study protocol requirements and has provided written informed consent. Exclusion Criteria: 1. The patient is currently taking medications that may interfere with the assessment of nausea or vomiting, including but not limited to other 5-HT3 receptor antagonists, NK1 receptor antagonists, psychotropic agents, or opioid analgesics; 2. The investigator determines that the patient's nausea or vomiting is highly likely attributable to anti-tumor treatments not involving antibody-drug conjugate (ADC) therapy; 3. The patient is deemed unsuitable for glucocorticoid or progesterone use; 4. The patient has a history of hypersensitivity to netupitant, palonosetron, or any excipient in the capsule formulation; 5. The patient has significant gastrointestinal conditions affecting oral drug absorption, such as dysphagia, chronic diarrhea, or intestinal obstruction; 6. The patient has a severe psychiatric disorder or difficulties understanding the study procedures, completing questionnaires, or communicating effectively in Chinese; 7. The investigator identifies any other condition that may compromise the conduct of the clinical study or the interpretation of its results.