ESTRO 2022 - Abstract Book

S1630

Abstract book

ESTRO 2022

accuracy of our equipment and tools is reliable. HR 3D CBCT scans performed pre SRTs further refine patient and target volume setting, support medical decision making and eliminate the possibility of gross error.

PO-1835 A glimpse at breast internal mammary chain radiotherapy practice in the United Kingdom

Z. Nabi 1 , R. Butt 2 , R. Mir 3 , J. Hills 2 , Y. Tsang 4 , D. Wheatley 5 , I.S. Bhattacharya 6 , A. Ranger 7 , S. Cramp 8 , N. Hammonds 9 , A. Goyal 10 1 National Radiotherapy Trials Quality Assurance Group (RTTQA), Radiotherapy Physics, Mount Vernon Cancer Centre., Middlesex, United Kingdom; 2 National Radiotherapy Trials Quality Assurance Group (RTTQA), Radiotherapy Physics, Mount Vernon Cancer Centre, Middlesex, United Kingdom; 3 Mount Vernon Cancer Centre, Clinical Oncology, Middlesex, United Kingdom; 4 Mount Vernon Cancer Centre, Radiotherapy, Mount Vernon Cancer Centre, Middlesex, United Kingdom; 5 Royal Cornwall Hospitals NHS Trust, Clinical Oncology, Cornwall, United Kingdom; 6 Cambridge University Hospitals NHS Trust, Clinical Oncology, Cambridge, United Kingdom; 7 The Royal Marsden Hospital NHS Foundation Trust, Clinical Oncology, London, United Kingdom; 8 University of Warwick, Warwick Clinical Trials Unit, Coventry, United Kingdom; 9 University of Warwick , Warwick Clinical Trials Unit, Coventry, United Kingdom; 10 Royal Derby Hospital, Department of oncoplastic breast surgery, Derby, United Kingdom Purpose or Objective Radiotherapy treatment of breast and regional nodes increasingly include internal mammary chain (IMC) as evidence has emerged showing survival benefits in patients with high risk of locoregional recurrence [1]. This study aimed to examine the variations of breast IMC radiotherapy practice in the United Kingdom (UK). Materials and Methods Axillary Management in Breast Cancer Patients With Needle Biopsy Proven Nodal Metastases After Neoadjuvant Chemotherapy (ATNEC), ClinicalTrials.gov: NCT04109079, is a randomised phase III trial investigating whether axillary treatment can be avoided in patients with no residual cancer in the lymph glands after chemotherapy. As part of the ATNEC Quality Assurance (QA) programme a pre-trial questionnaire was circulated to centres that expressed an interest in participating in the trial. The questionnaire was designed to capture participating centres’ breast IMC radiotherapy practice in terms of target volume delineation, radiotherapy planning techniques, motion management and treatment verification approaches. Results Between September 2019 to August 2021, 27 UK centres completed the questionnaires and the results were summarised in figure 1. ATNEC mandates target volume delineation for radiotherapy planning and 16/27 centres (59%) did not routinely delineate regional nodes. For treatment planning techniques, 17/27 centres were using volumetric modulated arc therapy (VMAT) and 20/27 centres used wide tangential techniques. All participating centres used deep inspiration breath hold (DIBH) as the motion management approach for delivery breast IMC radiotherapy. In terms of treatment verification, the practice varied from centre to centre and were mostly dependent on the use of planning technique and fractionation regime. 2D MV/KV imaging (21/27 centres) were most commonly used; Cone-beam computed tomography (CBCT) was used by some centres when VMAT technique was employed. It is noted all Elekta centres used CBCT for treatment verification. There were some variations in the frequency of imaging; 4 centres used daily CBCT for image verification, whereas the majority of the centres imaged using kV imaging on the first three fractions followed by weekly imaging.