ESTRO 2020 Abstract book

S82 ESTRO 2020

Kaplan-Meier method. The prognostic factors were identified by using the Cox regression hazards model. Results A total of 2047 patients were included in the study and the median radiation dose delivered is 5940cGy. Out of the entire cohort, 991 patients were allocated into the low- dose group (RT dose 4000-5939cGy) while 1056 patients were allocated into the high-dose group (RT dose ≥5940cGy). One-and 5-year OS were significantly better among patients in the high-dose group. Survival rates at 1 year were 52 % and 44% in the 2 groups, respectively. Survival rates at 5 years were 16% and 11% (p<0.0001) in the two groups, respectively. The prognostic factors for OS include radiation dose delivered, sex, cancer site, clinical T/N status, and body mass index. In subgroup analysis, those in the high-dose group showed a significant survival benefit in patients with cT3N1 (p= 0.0076), cT4N2 (p = 0.02) and cT4N3 (p = 0.0215) stage.

SP-0155 Is heart dose matter more important in SBRT than 3DCRT? Y. Kirova 1 1 Institut Curie Ensemble Hospitalier, Department of Radiation Oncology, Paris cedex 05, France Abstract text Extracranial stereotactic external-beam radiation therapy (SBRT) has developed considerably in recent years and is now an important part of the therapeutic alternatives to be offered to patients with cancer. It offers opportunities that have progressively led physicians to reconsider the therapeutic strategy, for example in the case of local recurrence in irradiated territory or oligometastatic disease. The literature on the subject is rich but, yet, there is no real consensus on therapeutic indications as well as clear guidelines concerning the doses at organs at risk (OAR), especially in the cardiac substructures. This is largely due to the lack of prospective, randomized studies that have evaluated this technique with sufficient recoil. The heart doses are very important for patients treated for lung or mediastinal tumours and the late complications of 3D conformal radiotherapy (3DCRT) are well known for patients presented with breast and thoracic tumours. However, RT- associated heart disease is often not manifested clinically until many years after RT, the clinical effectiveness of these approaches is less certain in patients treated by SBRT. The problem of the series with thoracic SBRT is that they are with small number of patients and short follow up period. Other important point is the high dose per fraction and this is not well known with the experience of 3DCRT. At the other hand, for patients with increased risk of cardiac complications, SBRT may present lower risks than surgery. The number of International Guidelines is limited but some examples are available for the everyday practice. For example, the RECORAD 2016 proposed in case of use of 3 fractions (of 15-18 Gy) schemes, to limit the maximal heart dose (Dose max) at < 30 Gy and D15ml<24Gy; in case of 5 fraction of 10Gy to respect the maximal dose (Dose max) at < 38 Gy and D15ml < 32Gy. The JROSG10-1 recommends D15cc < 40 Gy in case of 8-10 fractions. Larger prospective data, with longer follow up is needed to evaluate the tolerated dose and the irradiated volume with multidisciplinary discussion to establish solid guidelines and decrease the risk of long term toxicity. PH-0156 Pattern of care and outcomes in stage III esophageal cancer receiving definitive chemoradiation Y. Chou 1 , Y. Lee 1 , J. Chiou 2 , H. Chen 1 , H. Tseng 1 , C. Huang 3 , J. Huang 4 1 Chung Shan Medical University Hospital, Radiation Oncology, Taichung, Taiwan ; 2 Chung Shan Medical University, School of Health Policy and Management, Taichung, Taiwan ; 3 Chung Shan Medical University Hospital, Institute of Medicine, Taichung, Taiwan ; 4 Chung Shan Medical University Hospital, Department of Medical Research, Taichung, Taiwan Purpose or Objective Multimodality approach is recommended to treat stage III esophageal cancer (EsoC). However, the most optimal radiation dose to be delivered for patients receiving definitive chemoradiotherapy (dCCRT) is still in debate. Here we report the pattern of care and survival outcomes for stage III EsoC patients receiving dCCRT in Taiwan. Material and Methods Patients who were diagnosed as having stage III EsoC and received dCCRT between 2010 and 2015 were retracted from the Taiwan Cancer Registry database for analysis. The overall survival (OS) rates were calculated by the Poster Highlights: Poster highlights 5 CL : GI

Conclusion In Taiwan, more than half of the stage III EsoC patients who were treated with dCCRT received a radiation dose greater than 5940cGy. The results of this study indicate that those received a higher radiation dose greater than 5940cGy had a better OS than those received a radiation dose lower than 5940cGy. PH-0157 Proton therapy achieves favorable dosimetric sparing and acute toxicity for esophageal cancer M. Chuong 1 , J. Chang 2 , A. Kaiser 3 , J. Zeng 4 , W. Hartsell 5 , H. Tsai 6 , C. Stevens 7 , C. Vargas 8 1 Miami Cancer Institute, Radiation oncology, Miami, USA ; 2 Oklahoma Proton Center, radiation oncology, Oklahoma City, USA ; 3 Maryland Proton Treatment Center, Radiation oncology, Baltimore, USA ; 4 University of Washington, Radiation oncology, Seattle, USA ; 5 Northwestern Medicine, radiation oncology, Chicago, USA ; 6 Procure Proton Therapy Center, radiation oncology, Somerset, USA ; 7 Beaumont Hospital, radiation oncology, Royal Oak, USA ; 8 Mayo Clinic, radiation oncology, Scottsdale, USA Purpose or Objective There is growing enthusiasm that the reduced normal organ dose achieved by proton beam therapy (PBT) versus x-ray therapy (XRT) may improve clinical outcomes for esophageal cancer (EC) patients. However, the extent of the published literature supporting PBT for EC remains limited and mostly consists of retrospective single institution reports. Material and Methods We evaluated clinical and dosimetric outcomes of EC patients treated with PBT who enrolled on the multi- institutional Proton Collaborate Group (PCG) REG001-09 trial (NCT01255748). This ongoing registry study captures prospectively recorded outcomes for patients treated with PBT according to institutional preference for a wide variety of cancer types including EC. To better understand the potential benefits of PBT we included only patients treated with curative intent and prescribed at least 41.4

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