ESTRO 36 Abstract Book

S631 ESTRO 36 2017 _______________________________________________________________________________________________

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. 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

Conclusion This study demonstrated the feasibility of capturing local temperature elevation over the course of adjuvant radiotherapy for breast cancer. Maximal and average local temperature increased for all patients, confirming the intensity of inflammatory phenomena linked to irradiation. Patients suffering from high-grade radiation- induced dermatitis radiated noticeably more heat. Furthermore, they started doing so before the occurrence of clinical signs of dermatitis. As such, thermography showed promising results as a predictive tool for the occurrence of acute skin toxicity. EP-1172 Post-mastectomy radiotherapy with patient- tailored bolus using 3D printing for left breast cancer K. Yang 1 , Y. Chung 1 , W. Park 1 , S.G. Ju 1 , S.J. Huh 1 , D.H. Choi 1 , H. Cha 1 , J.Y. Park 1 , C.H. Na 1 1 Samsung Medical Center, Radiation Oncology, seoul, Korea Republic of Purpose or Objective Radiation exposure to the heart during radiotherapy for left breast cancer patients has a chance to increase the risk of cardiovascular disease. Also, radiation pneumonitis and decreased lung function associated with thoracic radiotherapy have been reported. The purpose of this study is to reduce heart and ipsilateral lung doses using an optimized chest wall electron beam therapy with patient- tailored bolus (PTB) using 3D printing technology for left breast cancer patients after mastectomy. Material and Methods Five patients with left breast cancer underwent computed tomography (CT) simulation for irradiation of left chest wall and supraclavicular fossa after mastectomy. We designed a virtual bolus on the chest wall to compensate the surface irregularities on CT images and developed a plan for chest wall electron beam therapy. Also, a rival plan for conventional tangential technique was done on the same CT. For both plans, supraclavicular field was planned using photon beam. For planning, virtual bolus was overridden by a density of material which would be used to make PTB with 3D printer. Dosimetric comparisons for target and organs at risk such as heart and ipsilateral lung were performed between the 3D PTB applied electron beam plan and tangential plan. Wilcoxon signed-rank test was used for statistical analysis. Results For cardiac dose, PTB applied electron plan showed lower D mean , D max . V5 Gy and V30 Gy than tangential plan (p=0.080, 0.043, 0.686 and 0.068, respectively). For ipsilateral lung, D mean and V20 Gy 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