Axillary Radiotherapy or Axillary Lymph Node Dissection in Patients With Clinically Node- Positive Breast Cancer Undergoing Upfront Tailored Axillary Surgery

Inclusion Criteria at screening: * Written informed consent according to ICH/GCP regulations prior to any trial specific procedures. * Patients ≥ 18 years of age. * Node-positive breast cancer (histologically or cytologically proven both in primary tumor and in lymph node) American Joint Committee on Cancer/ International Union Against Cancer (AJCC/UICC) stage II-III (all molecular subtypes allowed). * Node-positivity detected by imaging and non-palpable (iN+) and confirmed by pathology. * Node-positivity palpable (cN1-3) and confirmed by pathology. * Occult breast cancer is allowed, if biopsy-proven axillary lymphatic metastasis is present. * Eligible for primary ALND or SLN procedure and either: * Newly diagnosed. * Isolated in-breast recurrence or second ipsilateral breast cancer after previous breast conserving surgery and sentinel procedure and at least 3 years disease free and no prior axillary dissection or axillary RT. * Upfront surgery setting. * Most suspicious axillary lymph node clipped. (If clipping is not part of the routine, this should be done after consent of the patient as a study procedure.) * Ability to complete the QoL questionnaires. * WHO performance status 0-2 * Adequate condition for general anesthesia, breast cancer surgery and radiotherapy. * Adult patients (≥18 years of age). * Women of child-bearing potential are using effective contraception (condom, diaphragm, intrauterine device), are not pregnant or lactating and agree not to become preg…