Efficacy Study of Herceptin to Treat HER2-negative CTC Breast Cancer

* Age ≥ 18 years * Written informed consent must be given according to ICH/GCP, and national/local regulations * Availability of peripheral blood draw for CTC blood test * Tumor block or minimum 10 unstained slides of 4 μm of primary tumor must be available prior to registration for centralized HER2 testing * ER status available * Adequately excised non-metastatic and non-relapsed operable primary invasive HER2-negative adeno-carcinoma of the breast \*: * the patient should have completed either * adjuvant chemotherapy or * neoadjuvant chemotherapy; in this case residual invasive disease in breast or lymph nodes is required (no complete pathological response) no further adjuvant chemotherapy treatment planned. Prior chemotherapy with doxorubicin restricted to a total dose of 360 mg/m2 or with epirubicin restricted to a total dose of 720 mg/m2 is allowed * No prior use of anti-HER2 therapy for any reason or immunotherapy for BC * No concomitant use of bisphosphonate therapy or denosumab for any reason. Prior use of these agents is allowed provided that last treatment has been received at least 4 weeks before registration in the study * No prior mediastinal irradiation except internal mammary node irradiation for the present BC * Concomitant adjuvant hormonal therapy or radiotherapy (if applicable) is allowed upon physician's choice * The interval between definitive surgery (neoadjuvant population) or end of adjuvant chemotherapy (adjuvant population) and registration must be a…