Inclusion Criteria:

- Patients with histologically confirmed breast cancer scheduled to receive
chemotherapy with doxorubicin and cyclophosphamide (adjuvant or neoadjuvant)

- Southwest Oncology Group (SWOG) performance status of 0-1

- Projected life expectancy of at least 3 months

- Provision of informed consent prior to any study-related procedures

- Negative pregnancy test for women of childbearing potential

- Absolute neutrophil count (ANC) >= 1500/mm^3

- Platelet count >= 100,000 cells/mm^3

- Hemoglobin >= 9.0g/dL

- Serum creatinine =< 1.5 mg/dl

- Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) =< 2.5 X upper
limit of normal (ULN)

- Alkaline phosphatase =< 2.5 X upper limit of normal; in patients with bone metastasis
and no evidence of liver metastasis and bilirubin =< upper limit of normal an
alkaline phosphatase =< 5 ULN will be allowed

- Serum bilirubin =< 1.0 mg/dL

- No other concomitant therapy directed at the cancer is allowed

Exclusion Criteria:

- Allergy or intolerance to 5HT3 or NK-1 antagonists and dexamethasone

- Use of another antiemetic agent (5HT3 antagonists, phenothiazines, butyrophenones,
cannabinoids, metoclopramide, or corticosteroids) within 72 hours prior to day 1 of
the study

- Use of anticoagulant agent (Warfarin, Coumadin, Jantoven, Marevan, Lawarin, Waran, or
Warfant)

- An episode of vomiting or retching within 24 hours before the start of the initial
treatment with chemotherapy

- Severe concurrent illness other than neoplasia

- Gastrointestinal obstruction or an active peptic ulcer

- Patients who are pregnant or breast feeding because aprepitant may be harmful to the
developing fetus and newborn