ExclUsive endocRine Therapy Or Radiation theraPy for Women Aged ≥70 Years Early Stage Breast Cancer

Inclusion Criteria: * Women aged ≥70 years; * histologically proven invasive adenocarcinoma of the breast; * pathological T1 (pT1) stage (clinical T1-2 \[cT1-2\] stage is allowed); * clinical and pathological N0 (cN0 and pN0) stage (isolated tumor cells \[i+\] allowed); * any tumor grade (if pT ≤10 mm), G1-2 tumor grade (if pT between 11 and 19 mm); * Luminal-A by immunohistochemistry (IHC)-based on local assessment (consistent with 14th St. Gallen consensus definition): * ER/PgR+ (defined as ≥10% by IHC staining), * Human epidermal growth factor receptor 2 (HER2)- (0 or 1+ following IHC staining and proven negative by in-situ hybridization \[ISH\] in case of 2+), and * Ki67 ≤20% by IHC staining; * surgically treated with BCS with or without sentinel node biopsy (SNB); * no clinical evidence of distant metastases. Imaging work up is not mandatory to enter the trial. If there are signs/symptoms suggesting the presence of local relapse or distant metastasis, an appropriate work up should be performed according to the treating physician standard practice. A patient with confirmed local relapse or distant metastasis will no longer be eligible for the trial; * postoperative final surgical margins negative (no ink on tumor); * baseline HRQoL questionnaires completion; * adjuvant bisphosphonates and denosumab are allowed; * before patient registration/randomization, written informed consent must be given. Exclusion Criteria: * Preoperative systemic treatments (i. e., chemo…