Aromatherapy Combined With Standard Antiemetic Therapy vs Standard Therapy Alone for Prevention of CINV in Breast Cancer Patients Receiving Highly Emetogenic Chemotherapy

Inclusion Criteria: * Histopathologically confirmed breast cancer (aged 18-80 years, inclusive). * Scheduled to receive or currently receiving intravenous chemotherapy, with at least 2 planned cycles. * Planned use of guideline-recommended triple antiemetic therapy (5-HT3 receptor antagonist + NK-1 receptor antagonist + dexamethasone). * ECOG performance status ≤ 2 and life expectancy ≥ 3 months. * Chemotherapy regimen classified as highly emetogenic risk according to CSCO, NCCN, or MASCC/ESMO antiemetic guidelines. * Able to understand the study procedures, voluntarily participate, and provide written informed consent. Exclusion Criteria: * History of allergy to essential oils. * History of vestibular dysfunction or intestinal obstruction. * Major cardiovascular or cerebrovascular event within the past 12 months (e.g., unstable angina, myocardial infarction, cerebral hemorrhage, cerebral infarction; asymptomatic lacunar infarction not requiring treatment is allowed). * Pregnancy, lactation, or possibility of pregnancy without willingness to use contraception. * History or current diagnosis of significant neurological or psychiatric disorders, including epilepsy or dementia. * Poor compliance anticipated, or any other condition that the investigator considers inappropriate for participation.