A Pharmacogenomics Study for Breast Cancer Patients Undergoing Adjuvant Chemotherapy With Doxorubicin (A)/Cyclophosphamide ©) and/or Weekly Paclitaxel

Eligibility Criteria * Histologically confirmed invasive breast cancer * node negative stage \> T1c or T1b with poor prognostic features (high grade, Her2/neu FISH positive, ER negative) or stage 2 (T2, N0) or * enrolled on CALGB 40101, CALGB 49909, or the National Cancer Institute of Canada study MA-21 or * any node positive patient or locally advanced undergoing neoadjuvant chemotherapy with either AC or paclitaxel * Age greater than or equal to 18 years. * \>/=2 weeks from major surgery (wide excision / lumpectomy / mastectomy) * No evidence of systemic metastasis * Undergoing adjuvant treatment with standard dose AC or AC followed by weekly Paclitaxel at 80mg/m2 * Adequate bone marrow, hepatic and renal functions (absolute neutrophil count \>1,500/ μl, platelet count \> 100,000/ μl, serum creatinine \<2.0 mg/dl, total Bilirubin \<2.0 x the upper limit of normal (ULN) * Ability to answer and understand study surveillance questionnaires * No concurrent drug therapy (within 2 weeks) with agents that are known inducers or inhibitors of Cytochrome P450 (CYP450). Exclusion Criteria * Other anticancer cytotoxic or endocrine therapy, immunotherapy, or biologic response modifiers,Study Drugs or other concomitant medications known to cause myelosuppression especially neutropenia and neuropathy * Eastern Cooperative Oncology Group Performance Status(ECOG) functional status \> 2. * Serious co-morbidities including poorly controlled diabetes mellitus, ischaemic heart disease,uncontrolled hypertension or active infection. * Pregnancy * Use of growth factor during cycle 1 of chemotherapy (AC) under pharmacokinetic evaluation * Grade \>/=2 peripheral neuropathy symptoms based on National Cancer Institute- Common Terminology Criteria for Adverse Events (NCI-CTCAE) Scale. Exception: a chronic neurologic disorder will be reviewed on a case by case basis by the study PI. * Prior treatment with weekly paclitaxelDISEASE CHARACTERISTICS: * Histologically confirmed invasive breast cancer, meeting 1 of the following criteria: * Node negative disease AND meets 1 of the following stage criteria: * Primary tumor \> T1c * Primary tumor \> T1b AND poor prognostic features, defined as the following: * High-grade disease * Human Epidermal Growth Factor Receptor 2 (HER2)/neu-positive disease by fluorescence in situ hybridization * Estrogen receptor-negative disease * Stage II disease (T2, N0) * Node positive nonmetastatic disease * Locally advanced disease AND receiving neoadjuvant chemotherapy comprising doxorubicin and cyclophosphamide OR paclitaxel * Enrolled in clinical trial CALGB-40101 * No evidence of systemic metastasis * Hormone receptor status: * Not specified