Sacubitril/Valsartan in PriMAry preventIoN of the Cardiotoxicity of Systematic breaST canceR trEAtMent (MAINSTREAM)

Inclusion Criteria: * Written informed consent * Female gender, aged 18 years and over * Patients with histologically confirmed breast cancer and complete assessment of tumor phenotype (Estrogen receptor - ER, Progesterone receptor - PR, Human epidermal growth factor receptor 2 - HER2, Kiel - Ki67) * Ability to take oral medication and willingness to adhere to the planned regimen * Tumor grade IA-IIIC or oligometastatic grade IV * Radical treatment plan including surgery * Plan of use of systemic treatment (preoperative, postoperative or combined) with anthracyclines and/or anti-HER2 drugs * Eastern Cooperative Oncology Group (ECOG) 0-2 general status * LVEF ≥ 50% as assessed by echocardiography * Sinus rhythm Exclusion Criteria: * Prior anthracycline-based chemotherapy and/or thoracic radiotherapy (prior to diagnosis of the cancer being the present cause of therapy) * Clinically relevant HF (NYHA II-IV) * Myocardial infarction (MI) within the last \< 3 months * Symptomatic hypotension or systolic blood pressure (SBP) \< 90 mmHg * Significant valvular disease, symptomatic coronary artery disease (CCS\>2), significant atrioventricular (AV) block, symptomatic sinus node dysfunction * Expected survival \<12 months * Glomerular filtration rate (GFR) \<30 ml/min/1.73 m2 (screening visit) * K+\>5.5mmol/L (screening visit) * Contraindications to angiotensin converting enzyme inhibitor (ACE-I)/angiotensin II receptor blocker (ARB) or LCZ696 if not listed among criteria * Active untreated liver disease * Pregnancy * Conditions/circumstances that may lead to non-compliance with medical staff recommendations (e.g. active drug/alcohol dependence, poorly controlled mental illness)