Doxorubicin Hydrochloride, Cyclophosphamide, Docetaxel, and S-1 Before Surgery in Treating Women With Stage II or Stage III Breast Cancer

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed invasive primary breast cancer * Clinical (radiologic) stage II or III disease * No T4d disease * No inflammatory breast cancer * ErbB2-negative disease OR patient cannot receive trastuzumab treatment * ErbB2-positive disease defined as either immunohistochemistry 3+, or FISH- or CISH-positive; immunohistochemistry 2+ is to be determined according to FISH or CISH results PATIENT CHARACTERISTICS: * Mobile * ECOG performance status 0-1 * Normal cardiac function (LVEF \> 50%) * Hemoglobin ≥ 10.0 g/dL * Absolute neutrophil count ≥ 1,500/μL * Platelet count ≥ 10 x 10\^4/μL * Creatinine ≤ 1.5 times upper limit of normal (ULN) OR creatinine clearance ≥ 50 mL/min * Total bilirubin ≤ 1.5 times ULN * AST/ALT ≤ 2.5 times ULN * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * Able to swallow tablet whole with water * No prior motor or sensory neurotoxicity CTCAE ≥ grade 2 * No other serious disease or medical condition * No uncontrolled or serious cardiovascular disease, including any of the following: * Myocardial infarction within the past 6 months * New York Heart Association class III or IV heart failure * Uncontrolled angina pectoris * Clinically significant pericardial disease * Cardiac amyloidosis * No history of symptomatic or therapy-requiring cardiac arrhythmia CTCAE grade 3 (e.g., multifocal premature ventricular contractions, bigeminy, trigeminy, ventricular tachycardia, uncontrolled atrial fibrillation) * No asymptomatic sustained ventricular tachycardia * History of atrial fibrillation or cardiac arrhythmia controlled by medication allowed * No uncontrolled infection, unstable peptic ulcer, uncontrolled diabetes, or any other contraindication to corticosteroid administration * No history of infection or any other serious medical event which may cause any functional injury in the affected patient and consequently, interfere with continuing the study treatment * No history of hypersensitivity to taxanes, fluorouracil, or S-1 * No significant gastrointestinal malfunction that will affect S-1 absorption * No history of other cancer within the past 5 years except properly treated carcinoma in situ of the uterine cervix or basal cell or squamous cell carcinoma of the skin * No severe psychological or neurological disorder or dementia that would preclude understanding of the informed consent * No psychological, social, family, or geographical condition, or difficult circumstance that would preclude follow-up or compliance with the protocol PRIOR CONCURRENT THERAPY: * No prior systemic treatment for this cancer (e.g., radiotherapy, chemotherapy, hormone therapy, or biological therapy) * No prior preoperative topical treatments (e.g., incomplete surgery or radiotherapy) for this cancer * No concurrent drug(s) that may potentially cause changes in the pharmacological activity of S-1 formulation, including any of the following: * Allopurinol * Phenytoin