Randomized Trial With Trastuzumab Versus Observation in Breast Cancer Patients

Inclusion Criteria: * Age \>= 18 years. * Performance status (World Health Organization \[WHO\]) \< 3 * Adequate bone marrow function (absolute neutrophil count \> 1000/mm\^3, platelet count \> 100000/mm\^3, hemoglobin \> 9 gr/mm\^3) * Adequate liver (bilirubin \< 1.5 times upper limit of normal and SGOT/SGPT \< 2 times upper limit of normal) and renal function ( creatinine \< 2 mg/dl) * Adequate cardiac function (left ventricular ejection fraction \[LVEF\] \> 50%). * Informed consent * Histologically or cytologically confirmed breast adenocarcinoma * Prior surgical excision of the primary breast tumor * Prior completion of standard adjuvant chemotherapy and/or radiotherapy * Locally advanced disease after the completion of neo-adjuvant chemotherapy, surgical excision and radiotherapy provided that there was no evidence of local or metastatic disease * Absence of any clinical or laboratory evidence of metastatic disease * Detection of CTCs and/or DTCs (when it could be feasible) before the initiation and/or after the completion of adjuvant chemotherapy and/or radiotherapy * Expression of HER2/c-neu on the primary tumor is not mandatory Exclusion Criteria: * Other invasive malignancy within the past 5 years except nonmelanoma skin cancer * Other concurrent uncontrolled illness * Psychiatric illness or social situation that would preclude study compliance * Pregnant or nursing * Positive pregnancy test * History of allergic reaction attributed to trastuzumab (HERCEPTIN)