Radiation therapy volumes after primary systemic therapy in breast cancer patients: an international EUBREAST survey

Purpose: After primary systemic therapy (PST), agreement on the extent of locoregional therapy is lacking in breast cancer patients who convert from a node-positive to a node-negative status. The aim of this survey was to investigate radiation therapy approaches after PST according to different axillary surgical strategies and disease responses. Materials and Methods: The European Breast Cancer Research Association of Surgical Trialists developed a web-based survey containing 39 questions on locoregional management based on clinical scenarios in initially node positive breast cancer patients undergoing PST. Twelve international breast cancer societies distributed the link to breast surgeons and radiation oncologists. Results: Responses from 349 breast specialists were recorded, 72 of whom (20.6%) were radiation oncologists from 17 countries. Nodal status at diagnosis informed the decision for postoperative regional nodal irradiation (RNI) for 44/72 (61.1%) responders. RNI in node positive patients having undergone axillary lymph node dissection (ALND) is delivered in selected cases by 30/72 (41.7%) responders and systemically recommended by 26/72 (36.1%) responders. In case of macrometastases found on ALND, 43/72 (59.7%) responders always deliver RNI. In case of micrometastases in the sentinel lymph node(s) or targeted lymph node(s), 45/72 (62.5%) responders prefer RNI to completion ALND. A majority of responders (59.7%) determine the target volume for RNI according to European Society for Radiotherapy and Oncology guidelines. Significant heterogeneity was observed regarding nodal basins and volumes of interest for dose coverage by RNI. Conclusions: There is significant heterogeneity in radiation-therapy delivered to the axilla after PST. A more standardized approach engaging both radiation oncologists and breast surgeons will help to optimize the harm-benefit equilibrium of axillary surgery and RNI.