Tamoxifen +/- GnRH Analogue vs Aromatase Inhibitor + GnRH Analogue in Male Breast Cancer Patients

Inclusion criteria 1. Written informed consent for all study procedures. 2. Complete baseline documentation sent to GBG Forschungs GmbH. 3. Male patients. 4. Age ≥ 18 years. 5. Karnofsky-Index ≥ 60%. 6. Histologically confirmed unilateral or bilateral carcinoma or of the breast at primary diagnosis (enrolment possible in neoadjuvant, adjuvant and metastatic situation). 7: No target lesion necessary for metastatic situation 8. Positive hormone receptor status (e.g. ER and/or PR-receptor positive). 9. Completed staging prior randomisation ( within 8 weeks after diagnose or last therapy (operation, chemotherapy or radiation), minimum: chest X-ray, ultrasound of the liver, bone scan). In case of positive findings, further investigations are required to verify the findings as clinically indicated. 10\. Prior chemotherapy is possible. In case of adjuvant treatment: adequate surgical treatment with histological complete resection including axillary lymph nodes if patients are included as adjuvant treatment. A sentinel lymph node biopsy is possible if the sentinel is not involved. 11\. Normal cardiac function must be confirmed by ECG within three months prior to randomisation. 12\. Laboratory requirements (≤ 14 days before therapy start): Hematology * Hemoglobin ≥ 9 g/dL, * Leukocytes 4 - 10 x1000/µL, * Thrombocytes 150 - 400 x1000/µL. Hepatic function * ASAT (SGOT) or ALAT (SGPT) ≤ 2x UNL, * Total bilirubin ≤ 2x UNL. Renal function * Serum creatinine ≤ 1.5x UNL, * Creatinine clearance \> 30 mL/min (if creatinine is above UNL, according to Cockroft-Gault). * Cholesterol 200 - 240 mg/dL (5.18 - 6.22 mmol/L), * HDL cholesterol \> 40 mg/dL (\> 1 mmol/L), * LDL cholesterol ≤ 160 mg/dL (≤ 4 mmol/L). * Prostate specific antigen (PSA) ≤ 2.5 ng/mL. 13. Two serum samples (5 mL) centrally made available. 14. Paraffin tumor tissue block and full blood sample centrally made available (except when the patient does not agree to central biomaterial collection). 15\. The patient must be accessible for treatment. Patients can simultaneously be registered in the register study of the University Hospital of Magdeburg. Exclusion Criteria 1. Female patients. 2. Prior endocrine therapy of breast carcinoma. 3. Known or suspected hypersensitivity reaction to the compounds or incorporated substances. 4. No indication for endocrine treatment. 5. Life expectancy of less than six months. 6. International Prostate Symptom Score (IPSS) \> 17. 7. Current diagnosis of a Prostate carcinoma. 8. History of prostate cancer within the last five years and regardless the time frame all patients with hormone receptor positive prostate carcinoma who have received endocrine treatment. 9. Concurrent neuronal or cardiac disease, poorly controlled arterial hypertension. 10. Previous thromboembolic event within the last five years (except from thromboembolic events correlated to implanted devices (e.g. port thrombosis) 11. Currently active hepatitis. 12. Disease significantly affecting gastrointestinal function, e.g. malabsorption syndrome, resection of the stomach or small bowel. 13. Concurrent treatment with other experimental drugs or participation in another clinical trial with any investigational, not marketed drug within 30 days prior to study entry. 14. Patients who are not able to give informed consent as defined according to AMG.