Abstract P1-15-09: Patterns of Practice of Regional Node Irradiation in the Sentinel Node Biopsy Era: Results of the Nodal Radiotherapy (NORA) Survey. on Behalf of the EORTC Breast Working Party of the Radiation Oncology Group (ROG)

Objective: Predicting the outcome of breast cancer (BC) patients based on sentinel lymph node (SLN) status without axillary lymph node dissection (ALND) is a matter of debate, especially when it comes to the definition of regional nodal irradiation (RNI). This is even unclear in the framework of primary systemic therapy (PST). The aim of the NORA (NOdal RAdiotherapy) Survey was to examine the patterns of RNI practiced by European Radiation Oncology centers. Methods: A web questionnaire was distributed to EORTC centers, and responses were received during the period between July 2013-January 2014. Results: A total of 81 European and 3 non-European answers were analyzed. While 3D planning is performed in 81 (96%) of the centers for breast irradiation, nodal areas are delineated in only 51 (61%) of the centers. After breast conserving surgery (BCS), only 14 (17%) centers declared to treat systematically the internal mammary chain (IMC), when supraclavicular node RT (SCN-RT) is indicated. Extra-capsular extension (ECE) is the main factor impacting decision-making regarding IMC and axillary nodal RT (ALN-RT). Only half of the centers advocate SCN-RT for intermediate risk patients (1-3N+). For macro-metastatic SLN involvement, there was a significant impact of ECE on decision-making independently from the number of positive LNs. In the PST setting, only 49 (58%) centers take into account the histologic fibrotic changes of the axillary LNs in post-PST ypN0 patients with unknown pre-PST status. In ypN0 patients with inner and central BC, 32 (39%) and 23 (27%) centers centers indicate SCN-RT and IMC-RT, respectively. SCN-RT is delivered by 30, 44, 58, 67 centers in patients with ypN(i+), ypN(mi), 1-2N+ and > 3-4N+ disease, respectively. ALN-RT is indicated by in 25% of the centers in patients with ypN(mi) or 1-2N+. Older age > 70y was not considered as a limited factor for RNI. Discussion: The term of RNI is not uniformly defined in the literature. In the historic studies, RNI was dedicated to wide RT including whole lymphatic pathways of the breast. ALN and IMC RT indications have declined with the time during the last decades because of the risk of morbidity. However this practice is challenged by the recent RT trials that reported and increase of overall and distant metastatic survival with RNI and IMC delivery in high-risk N0 and inner-central tumors. In addition, AMAROS trial showed equivalence between axillary RT and ALND in SLN (mi+) patients. Taking these data altogether in the context of increased avoidance of ALND, future challenges should concern the multidisciplinary patients’ selection for RNI and better personalization of the lymphatic pathways RT according to the risk of locoregional and distant recurrences. Conclusions: The NORA Survey is unique by evaluating the impact of SLN status and PST on RNI decision-making. IMC RT is not frequently coupled to SCN-RT. ECE is the main factor impacting decision-making for RNI. Only 58% of the centers take fibrotic changes in the LNs into consideration in decision-making for RNI indications. Age is not considered as a limiting factor for prescribing RNI in Europe. Citation Format: Yazid Belkacemi, Orit Kaidar-Person, Philippe Poortmans, Mahmut Ozsahin, Maria-Clara Valli, Nicola Russell, Ian Kunkler, Julie Hermans, Abraham Kuten, Geertjan van Tienhoven, Helen Westenberg. Patterns of practice of regional node irradiation in the sentinel node biopsy era: Results of the nodal radiotherapy (NORA) survey. On behalf of the EORTC Breast Working Party of the Radiation Oncology Group (ROG) [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-15-09.