ESTRO 2020 Abstract Book

S654 ESTRO 2020

asymptomatic cavernomas 21, 9 and 6 months after PT, respectively. Conclusion Our experience shows that PT can be a viable option for pediatric CNS tumors, even in the case of young children, achieving good disease control and only limited toxicity. However, a longer follow-up and more patients are needed to better evaluate long-term results. PO-1242 Early radiotherapy and high-dose chemotherapy improve survival of atypical teratoid rhabdoid tumors W.C. Yang 1 , Y. Hu 1 , Y. Chen 1 1 Taipei Veterans General Hospital, Division of Radiation Oncology- Department of Oncology, Taipei, Taiwan Purpose or Objective The optimal treatment strategy for pediatric atypical teratoid rhabdoid tumor (ATRT) is inconclusive. This study evaluated the prognostic value of early radiotherapy (RT) and high-dose chemotherapy with autologous stem cell rescue (HDC/ASCR) in pediatric ATRT and the possible treatment effect heterogeneities related to patient age. Material and Methods This pooled analysis included ATRT patients treated at our institution and from other studies who were identified by a search of the PubMed electronic database. The effect of patient demographics and treatment profiles on progression-free survival (PFS) and overall survival (OS) were analyzed using Cox regression. Results Overall, 34 patients from our institution and 436 patients from 35 published studies were included. Among Asian studies, the patients were older (mean age 44.3 vs. 34.0 months, p =0.051) and infra-tentorial tumors were more common (67.0 vs. 52.7%, p =0.012). The median follow-up time from diagnosis for all patients was 18.0 months, and the median follow-up time from diagnosis for those who were alive at the end of follow-up was 48.0 months. In multivariable analysis, patients with gross total resection (GTR), early RT (time to RT interval <2 months), and HDC/ASCR had both better PFS (hazard ratio [HR]=0.46, p 0.001; HR=0.64, p =0.011; and HR=0.51, p =0.005, respectively) and OS (HR=0.55, p =0.002; HR=0.48, p 0.004; and HR=0.42, p 0.001, respectively). For patients aged <3 years, both RT and HDC/ASCR were significant favorable factors for PFS (HR=0.32 and 0.46, respectively) and OS (HR=0.40 and 0.36, respectively), while early RT was not prognostic. For patients aged ≥3 years, early RT was significantly associated with better PFS (HR=0.51) and HDC/ASCR did not affect PFS, and neither was related to OS. Conclusion Both early RT initiation and HDC/ASCR were important components in the treatment of pediatric ATRT. The demographics varied between Asian and non-Asian patients. In addition, the treatment strategies that substantially affected the outcomes differed between patients aged ≥3 and <3 years. Thus, further subclassification of ATRT in clinical studies warrants investigation. PO-1243 20 years trend in the paediatric radiooncology: monocentric analysis M. Pazos 1 , A. Yermentayeva 1 , S. Schönecker 1 , O. Roengvoraphoj 1 , M. Rottler 1 , M. Albert 2 , I. Schmid 2 , V. Binder 2 , T. Feuchtinger 2 , F. Manapov 1 , C. Belka 1 1 LMU Munich, Radiation oncology, Munich, Germany ; 2 LMU Munich, Paediatric clinic Dr. von Haunersche, Munich, Germany Purpose or Objective The treatment protocols for paediatric patients with oncological diseases have changed over the last 20 years and consequently the number of patients who have to

receive radiotherapy as part of multimodal concepts. The evaluation of these trends in the paediatric radiooncology is the first step to get “real-life” numbers for a better planning of the resources. Material and Methods Between 04/1999 and 09/2019 all patients under 21 years old who had been irradiated in one reference university center were retro- and prospectively included in an observational study (Project Nr 18-337, ethics votum 21.08.2018). The recorded variables were: age, gender, type of tumor, type of RT treatment (2D, 3D, IMRT, VMAT), aim of RT (definitive, adjuvant, palliative), RT-Dosis, special techniques (total body irradiation (TBI), whole lung (WL)), OS and rate of second primary cancers. Four time- periods were compared: 1999-2003, 2004-2008, 2009- 2013, 2014-2019. Results Overall circa 12050 patients (pat) were treated in the radiotherapy department between 2009 and 2019, 518 pat (4.3%) being paediatric/young adult patients. Median age was 11.3 years; 228 girls (44%)/ 290 boys (56%). The cancer types distribution was: brain (24%), leukemia (21%), lymphoma (19%), sarcoma (16%), Wilms (5%), neuroblastoma (6%), others (9%). Most of the patients (90%) were treated with 3D-plans until 2016. After 2016 85% of the patients were irradiated with VMAT. The aim of RT was 50% adjuvant, 20% definitive and 30% palliative. After a median follow-up of 5.0 years (0-18.8years) 122 patients had died (24%), 314 patients were alive (60%) and 82 patients were lost of follow-up (16%). The rate of second primary cancers was 3.2%. The absolute numbers of irradiated patients stayed stable over the last three time-periods (1999-2003: 93 pat; 2004-2008: 135 pat; 2009-2013: 152 pat; 2014-2019: 138pat) but there was a significant trend towards higher percentage of patients with brain tumors (from 19% to 28%) and sarcoma (from 12% to 17%) and lower percentage of patients with lymphoma (from 30% to 14%). The rate of patients treated with leukemia didn´t changed over the years (21%), although the absolute number of TBI decreased in the last time-periods (1999-2003: 14 pat; 2004-2008: 37 pat; 2009- 2013: 21 pat; 2014-2019: 13 pat). Conclusion In the last 20 years the percentage of irradiated paediatric patients with lymphoma and also the absolute number of TBI have continuously decreased. This reflects the changes in the multimodal oncology treatment protocols over time. The RT-treatments for sarcoma and brain tumors have increased in the last time-periods and are oftener treated with modern radiation techniques (IMRT/ VMAT). The rate of second primary cancers (3.2%) is consistent with the published data, although a longer follow-up is needed. PO-1244 Neuroradiological abnormalities and toxicity following proton therapy (PT) of CNS pediatric tumors B. ROMBI 1 , A. Ruggi 2 , F. Toni 3 , L. Ronchi 4 , M. Buwenge 4 , I. Ammendolia 4 , S. Cammelli 4 , A. Prete 2 , M. Maffei 3 , I. Giacomelli 1 , M. Amichetti 1 , G. Morganti 4 , F. Melchionda 2 1 Proton Therapy Center - Santa Chiara Hospital, Department of Oncology, Trento, Italy ; 2 University of Bologna- S. Orsola-Malpighi Hospital, Department of Pediatrics, Bologna, Italy ; 3 Institute of Neurological Science of Bologna IRCCS, Pediatric Neuroradiology, Bologna, Italy ; 4 University of Bologna- S. Orsola-Malpighi Hospital, Radiation Oncology Center- Dept. of Experimental- Diagnostic and Specialty Medicine – DIMES, Bologna, Italy Purpose or Objective This monocentric study evaluated morphological and vascular neuroradiological abnormalities and toxicity following proton therapy (PT) of pediatric patients with CNS tumors. Material and Methods