ESTRO 2021 Abstract Book

S923

ESTRO 2021

DIBH significantly decreased doses to heart for proton and photon radiotherapy. DIBH increases lung dose in proton plans. For photons, significant dose-reduction to heart and lung establishes the role of DIBH in radiotherapy of breast and regional lymph nodes in the prone crawl position.

PO-1109 Regional Nodal Irradiation for Node Positive Breast Cancer: Clinical Outcomes Reporting A. Peters 1 , S. Anderson 1 , H. Marashi 1 , G. Lumsden 1 , A. Alhasso 1 , D. Cartwright 2 , O. O'Brien 3 1 Beatson West of Scotland Cancer Centre, Clinical Oncology, Glasgow, United Kingdom; 2 Beatson West of Scotland Cancer Centre, Medical Oncology, Glasgow, United Kingdom; 3 Beatson West of Scotland Cancer Centre, Radiology, Glasgow, United Kingdom Purpose or Objective Breast cancer patients with positive lymph node disease are currently recommended axillary node clearance (ANC) or RNI. ANC is associated with multiple complications such as lymphoedema, brachial plexopathy and shoulder stiffness. AMAROS conducted a non-inferiority trial showing RNI had similar OS, Cancer Specific Survival (CSS), DMFS and Local Regional Recurrence (LRR) as ANC, with better QoL post treatment. We re- explored this concept using local data from patients based at the Beatson Oncology Centre to see if outcomes from a real world population are similar. Materials and Methods 190 patients were recruited to receive RNI as opposed to ANC between 2006-2009. Patients had a range of different breast cancer subtypes/tumour grades. All patients had positive axillary disease, identified by either ANS or SLNB. Sy stemic therapy was given as per standard protocol and depending on tumour biology . Our data was compared to patients who had RNI (681) in AMAROS . Patients were followed up retrospectively, and OS, CSS, DMFS, LRR and treatment toxicity was recorded including lymphoedema/brachial plexopathy/shoulder stiffness. Survival analysis was performed on R via KM method. Univariate and multivariate analysis was also performed. Toxicity data was reported as percentages. Results 5 and 10 year CSS for our cohort was 95% and 88%. The corresponding 5 year CSS for AMAROS RNI 92.5%. Our 10 years OS was 74% Vs AMAROS cohort being 81.4%. DMFS at 5 years and 10 years was 86% and 72% vs AMAROS RNI arm of 82.7% and 78.2%. Our LRR was 3.16% at 14 years vs AMAROS RNI of 1.82% at 10 years. Lymphoedema rates in our cohort were 5.8% at 14 years. In AMAROS this was 11% at 5 years in the RNI group and 23% in the ANC group. Our brachial plexopathy was 1.6% and arm/shoulder stiffness 7.4%. AMAROS conducted a QoL survey pertaining to arm and shoulder stiffness/mobility/function which affected 18% in the RNI arm.