ESTRO 2020 Abstract book

S271 ESTRO 2020

Conclusion Results of this study suggest that SRT concurrent to TKI treatment in metastatic patients achieves good local metastasis control. There was no difference in OS or PFS whether TKIs were paused during SRT or not. Overall, severe toxicity of combined treatment was rare; however, SRT-induced toxicity was mainly observed when SRT was performed concurrently to EGFR inhibitors or BRAF(±MEK) inhibitors. OC-0454 Current radiotherapy practice for children with metastases from solid tumors: SIOPE survey analysis S. Huijskens 1 , P. Kroon 1 , C. Demiroz Abakay 2 , B. Timmermann 3 , J. Giralt 4 , M. Gaze 5 , S. Harrabi 6 , G. Scarzello 7 , A. Alexopoulou 8 , L. Padovani 9 , A. Escande 10 , L. Gandola 11 , S. Supiot 12 , M. Chojnacka 13 , J. Bokun 14 , A. Napieralska 15 , B. Rombi 16 , J.H. Maduro 17,18 , S. Bolle 19 , A. Mussano 20 , H. Mandeville 21 , L. Claude 22 , E. Seravalli 1 , G.O. Janssens 1,18 1 University Medical Center Utrecht, Radiation Oncology, Utrecht, The Netherlands ; 2 Uludag University, Radiation Oncology, Bursa, Turkey ; 3 University Hospital Essen, Department of Particle Therapy, Essen, Germany ; 4 Vall d’Hebron University Hospital, Radiation Oncology, Barcelona, Spain ; 5 University College London Hospitals NHS Foundation Trust, Radiation Oncology, London, United Kingdom ; 6 Heidelberg University Hospital, Radiation Oncology, Heidelberg, Germany ; 7 Veneto Institute of Oncology, Radiation Oncology, Padua, Italy ; 8 Athens General Children's Hospital, Radiation Oncology, Athens, Greece ; 9 Centre hospitalo universitaire, Radiation Oncology, Marseille, France ; 10 Oscar Lambret comprehensive Cancer Center, Radiation Oncology, Lille, France ; 11 Fondazione IRCCS Istituto Nazionale dei Tumori, Radiation Oncology, Milan, Italy ; 12 Institute de Cancerologie de l’Ouest, Radiation Oncology, Nantes, France ; 13 Maria Skłodowskiej-Curie Memorial Cancer Center-Institut, Radiation Oncology, Warsaw, Poland ; 14 Institute of Oncology and Radiology of Serbia, Radiation Oncology, Belgrade, Serbia ; 15 Maria Skłodowska-Curie Cancer Centre, Institute of Oncology, Gliwiche, Poland ; 16 Trento Hospital, Proton Therapy Center, Trento, Italy ; 17 University Medical Center Groningen, Groningen Proton Center, Groningen, The Netherlands ; 18 Princess Maxima Center, Radiation Oncology, Utrecht, The Netherlands ; 19 Gustave Roussy, Radiation Oncology, Villejuif, France ; 20 Citta della Salute e della Scienza, Radiation Oncology, Torino, Italy ; 21 The Royal Marsden, Radiation Oncology, Sutton, United Kingdom ; 22 Centre Leon Berard, Radiation Oncology, Lyon, France Purpose or Objective At diagnosis, around 20% of children with solid tumors present with distant metastases. The use of radiotherapy (RT) on metastatic sites to improve outcome is often topic of discussion. Data on the use of RT with curative intent to metastatic sites from solid tumors in children is sparse, and protocol guidelines are insufficient. The aim of this survey was to map the current practice across SIOPE- affiliated countries. Material and Methods SIOPE centers irradiating at least 50 children annually were invited to participate. The online accessible survey with 44 questions focused on patient selection and treatment techniques in pediatric patients undergoing RT on metastases from solid tumors (rhabdomyosarcoma, Ewing sarcoma, soft-tissue sarcoma, neuroblastoma and renal tumors).

Results Between July and September 2019, 21/27 centers (78%) answered the survey. These centers irradiate on average 17 children annually (range 4-55 per center, totaling 361 children) on metastatic sites (bone/bone marrow, brain, non-regional lymph nodes, lung, and liver), of which half of them (n=183 patients) with curative intent (Fig1A).

Over 75% of RT-centers irradiate lung and lymph node metastases across all tumor types, with a curative intent (Fig1B). Poor prognosis is the major concern for not delivering RT with curative intent (Fig2A). Additionally, the total volume and number of lesions are important factors. Most centers (60%) apply a maximum number of metastatic sites (Fig2B). If the number is the limiting factor at presentation, 75% of the centers reported that re-evaluation after neo-adjuvant chemotherapy is done to re-consider curative RT.

A rotational photon technique (>85% indicated the use of VMAT / coplanar method) and a pencil beam scanning technique are the preferred techniques. Except for brain lesions, a non-coplanar method using photons was more frequently used. Over 85% of the participating centers apply a conventional fractionation regimen for all tumor types and sites, with some exception for brain metastases where a tendency to use stereotactic RT was more often