Adjuvant Paclitaxel and Trastuzumab for Node-Negative HER2-Positive Breast Cancer

Inclusion Criteria: * Histologically confirmed invasive carcinoma of the breast * Tumors must be less than or equal to 3cm in greatest dimension * Must have node-negative breast cancer according to teh AJCC 7th edition * ER/PR determination is required. ER- and PR-assays should be performed by immunohistochemical methods * HER-2 positive: IHC 3+ or FISH \>2 * Bilateral breast cancers that individually meet eligibility criteria are allowed * Patients should have tumor tissue available, and a tissue block of sufficient size to make 15 slides must be sent to DFCI for testing * Less than or equal to 84 days from mastectomy or from axillary dissection or sentinel node biopsy if the patient's most extensive breast surgery was a breast-sparing procedure * All tumor should be removed by either a modified radical mastectomy or a segmental mastectomy (lumpectomy), with either a sentinel node biopsy or axillary dissection * 18 years of age or older * ECOG Performance Status of 0 or 1 * Adequate bone marrow function, hepatic function, and renal function as outlined in protocol * Left ventricular ejection fraction of greater than or equal to 50% * Willingness to discontinue any hormonal agent prior to registration and while on study * Willingness to discontinue sex hormonal therapy, e.g. birth control pills, prior to registration and while on study * Patients with a history of ipsilateral DCIS are eligible if they were treated with wide-excision alone, without radiation therapy * Patients undergoing breast conservation therapy must not have any contraindications to radiation therapy Exclusion Criteria: * Pregnant or nursing women * Locally advanced tumors at diagnosis, including tumors fixed to the chest wall, peau d'orange, skin ulcerations/nodules, or clinical inflammatory changes * History of prior chemotherapy in past 5 years * History of prior trastuzumab therapy * Active, unresolved infection * Prior history of any other malignancy in the past 5 years, except for early stage tumors of the skin or cervix treated with curative intent * Sensitivity to benzyl alcohol * Grade 2 or greater neuropathy per NCI's CTCAv3.0. (Exception: Any chronic neurologic disorder will be looked at on a case-by-case basis by the study chair). * Active cardiac disease as outlined in protocol.