ESTRO 36 Abstract Book

S637 ESTRO 36 _______________________________________________________________________________________________

Conclusion In tackling inequitable access to HWBRT, a rational, evidence-based approach should ideally converge with professional perspectives, the factors influencing the interpretation of the evidence, and the organisational context, including existing dissemination channels. EP-1174 impact of radiotherapy to posterior supraclavicular and posterior triangle area in breast cancer S.H. Liu 1 , Y.C. Huang 2 , Y.J. Chen 1 1 Mackay Memorial Hospital, Department of Radiation Oncology, Taipei, Taiwan 2 Graduate Institute of Chinese Medical Science, China Medical University, Taichung, Taiwan Purpose or Objective For patients with 4 or more lymph nodes involvement, regional nodal irradiation (RNI) is associated with increased locoregional control and overall survival (OS). The main radiotherapy (RT) volume for RNI includes axillary, supraclavicular, and/or internal mammary nodes. However, whether the posterior supraclavicular area and the posterior triangle of the neck (PSPT) should be included in RNI remains unclear. The object of this study was to retrospectively review our clinical experience of RNI to PSPT or not in N2-3 breast cancer patients as a reference for target delineation. Material and Methods Patients with N2-3 breast cancer who received definitive surgery and/or neoadjuvant/adjuvant therapy during 2006–2013 were reviewed. The delivery of adjuvant RT and the coverage for RNI were at the discretion of treating physicians. To ensure precise delineation and dosimetry, only patients treated using the technique of intensity- modulated radiotherapy (IMRT) to regional nodal area were enrolled. The patterns of recurrence including the PSPT region were examined. The locoregional control rate (LCR), distant metastasis-free rate (DMFR), disease-free survival (DFS), and OS were analyzed using Kaplan-Meier method, and survival estimates were obtained with log- rank test and the Cox proportional hazard model. Results Of 256 N2-N3 breast cancer patients who were diagnosed and received operation in a medical center, 184 cases were eligible for the study. Among these women, 62 received RNI according to the recommended volume by RTOG consensus (RC group), 57 had additional volumes of PSPT (RC+PSPT group), and 65 did not have adjuvant RT (NRT group). Median follow-up was 62.8 months for the entire cohort. There was higher LCR (p=0.006, 90.8% vs. 78.5% at 5 years) and OS (p=0.007, 82.7% vs. 64.8% at 5 years) for the patients with adjuvant RT (RC and RC+PSPT) compared to those without RT (NRT). No difference in DMFR (p=0.508, 69.6% vs. 63.4% at 5 years) and DFS (p=0.243, 68.2% vs. 69.2% at 5 years) were noted. Among women with adjuvant RT, there was no statistical difference between RC and RC+PSPT groups (LCR: p=0.693, 93.1% vs. 89.9% at 5 years; DMFR: p=0.501, 66.2% vs. 73.9% at 5 years; DFS: p=0.606, 66.2% vs. 71.6% at 5 years; OS: p=0.548, 83.5% vs. 83.5% at 5 years). In details, locoregional recurrence was found in 4 (6.5%), 6 (10.5%), and 17 (26.2%) patients in the RC, RC+PSPT and NRT group, respectively. Among these patients, no PSPT recurrence was noted in RC+PSPT group, whereas there were 2 (50%) in the RC group and 11 (64.5%) in the NRT group. Conclusion Adjuvant RNI significantly increased LRC and OS for N2-N3 breast cancer patients. Local recurrence specifically noted in PSPT might be diminished by additional inclusion in the regional nodal irradiation volumes. This impact may not translate to the changes in LCR, DMFS, DFS, and OS in our experience. Further prospective investigation is

D mean of electron plan were lower (p=0.080 and 0.043, respectively) than those of tangential plan, while D max between two plans were less different. For target coverage, all of D mean , D max , D min , conformity index (CI) and homogeneity index (HI) of electron plan were higher than those of tangential plan (p=0.043, 0.043, 0.043, 0.225, 0.034, respectively). Conclusion Chest wall electron beam therapy with PTB reduced high dose exposed cardiac and lung volume with clinically acceptable target coverage compared with tangential technique. Postmastectomy radiotherapy using PTB might be effective for left breast cancer patients to reduce risk of cardiac disease and lung morbidity. EP-1173 Understanding variations in the use of hypofractionated radiotherapy for breast cáncer J.M. Borras 1 , J. Prades 1 , M. Algara 2 , J.A. Espinàs 1 , B. Farrús 3 , M. Arenas 4 , V. Reyes 5 , V. Garcia-Reglero 6 , M.J. Cambra 7 , E. Rubio Calatayud 8 , L. Anglada 9 , A. Eraso 10 , A. Pedro 11 , M.J. Fuentes-Raspall 12 , V. Tuset 13 1 Institut Català d'Oncologia, Cancer plan, L'Hospitalet de Llobregat, Spain 2 Hospital de l'Esperança- Parc de Salut Mar, Radiotherapy, Barcelona, Spain 3 Hospital Universitari Clinic de Barcelona, Radiotherapy, Barcelona, Spain 4 Hospital Universitari Sant Joan de Reus, Radiotherapy, Reus, Spain 5 Hospital Universitari Vall d´Hebron, Radiotherapy, Barcelona, Spain 6 Hospital Universitari Arnau de Vilanova, Radiotherpy, Lleida, Spain 7 Hospital General de Catalunya- Institut Oncològic del Vallès, Radiotherpay, Barcelona, Spain 8 Consorci Sanitari de Terrassa, Radiotherapy, Terrassa, Spain 9 Institut Català d'Oncologia- Girona, Radiotherapy, Girona, Spain 10 Institut Català d'Oncologia, Radiotherapy, L'Hospitalet de Llobregat, Spain 11 Hospital Clínica Plató, Radiotherapy, Barcelona, Spain 12 Hospital de la Santa Creu i Sant Pau, Radiotherapy, Barcelona, Spain 13 Hospital Universitari Germans Trias i Pujol, Radiotheraoy, Badalona, Spain Purpose or Objective Radiation oncology guidelines favour hypofractionated whole-breast radiotherapy (HWBRT) over more conventional schemes in the conservative treatment of breast cancer, but its adoption still varies in clinical practice. This study assessed the patterns of HWBRT use and adoption in Catalonia (Spain). Material and Methods We used a mixed-methods approach based on an explanatory sequential design, first collecting and analysing quantitative data on HWBRT use (> 2.5 Gy per fraction) in 11 public radiotherapy centres (2005–2015) and then performing 25 semi-structured interviews with all department heads and reference radiation oncologist/s. Results Of the 34,859 patients fulfilling the study criteria over the study period, just 12% were hypofractionated, reaching a rate of 29% in 2015 (p<0.001). Our analysis showed a narrowing age gap between patients receiving conventional fractionation and hypofractionation in centres leading adoption. However, there were important differences in clinicians’ interpretation of evidence and selection of patients for specific indications, both within and between departments. Clinical management of radiotherapy departments played a major role. and V20 Gy