This phase III, multicenter, randomized, open-label trial evaluates whether aromatherapy plus standard antiemetic therapy improves complete response (CR) of CINV compared with standard therapy alone in breast cancer patients receiving highly emetogenic chemotherapy (HEC). Despite guideline-recommended triple prophylaxis (5-HT3 antagonist, NK-1 antagonist, dexamethasone), 30-50% of patients still develop delayed CINV. Aromatherapy with lemon, lavender, and peppermint essential oils may provide additive benefit through olfactory-limbic and vagal pathways, but phase III evidence is lacking. 374 patients (aged 18-80) scheduled for at least two HEC cycles will be randomized 1:1, stratified by prior CINV. On chemo day, aromatherapy starts 30 min before and continues until 2 h after chemotherapy; on days 2-5, inhalation is at least 2 h daily.Primary endpoint: complete response (no vomiting, no rescue antiemetic) over 0-120 h. Key secondary endpoints: acute and delayed CR rates, complete/total control rates, time to treatment failure, quality of life (FLIE), anxiety, depression, sleep quality, and safety. Exploratory: plasma GDF15 dynamics and predictive value.
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.
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.