Inclusion Criteria:

- Female gender

- WHO performance status 0-1

- Non-metastatic and non-relapsed operable primary invasive HER2 negative
adeno-carcinoma of the breast that is adequately excised and all of the following:

- histological grade > 1 at the time of surgery (all patients) and primary tumor
size > 1 cm

- the patient should have completed either

- adjuvant chemotherapy for node-positive disease (pN ≥1, macrometastasis only) or

- neoadjuvant chemotherapy. In this case, no pathological complete response
(defined as any residual invasive disease in breast or lymph nodes) after
neoadjuvant chemotherapy is required.

- Availability of peripheral blood draw for CTC blood test

- Tumor block or unstained slides of primary tumor must be available prior to
randomization for centralized HER2 testing

- 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.

- Adjuvant hormonal therapy or adjuvant radiotherapy (if applicable) is allowed upon
physician's choice

- The interval between definitive surgery (neoadjuvant group) or end of adjuvant
chemotherapy (adjuvant group) and registration must be at least 3 weeks but no more
than 12 weeks.

Exclusion Criteria:

- No further adjuvant chemotherapy treatment planned.

- No prior use of anti-HER2 therapy for any reason or other prior use of biological
agent or immunotherapy for BC

- No prior and/or concomitant use of bisphosphonate therapy for any reason is allowed.

- No prior mediastinal irradiation except internal mammary node irradiation for the
present BC

- No history of prior (ipsilateral and/or contralateral) invasive breast carcinoma or
ductal carcinoma in situ.

- No history of any malignant neoplasms in the past 5 years except for curatively
treated basal and squamous cell carcinoma of the skin.

- No history of serious cardiac illness or other concurrent serious diseases that may
interfere with planned treatment, including severe pulmonary conditions. Baseline
LVEF≥55% measured by echocardiography or MUGA scan (performed 2 weeks before
randomization)

Eligibility Criteria at patient randomisation:

- ≥1CTC/15mL of blood by CellSearch® between 3 weeks and up to 12 weeks after surgery
(neoadjuvant population) or end of adjuvant chemotherapy (adjuvant population).

- Centrally confirmed HER2-negative primary BC. Centralized HER2 testing will be
performed in the surgical tumor specimen. A HER2-negative primary BC sample eligible
for randomization should have HER2 IHC scores of 0 or 1+ or 2+ AND should be HER2
FISH negative in central testing.

- Baseline LVEF≥55% measured by echocardiography or MUGA scan (performed within 2 weeks
prior to randomization)

- No evidence of unresolved or unstable serious toxicity from prior surgery, adjuvant
chemotherapy or radiotherapy

- No concurrent participation in another trial.

- Written informed consent must be given according to ICH/GCP, and national/local
regulations