Abstract Book

S175

ESTRO 37

OC-0329 Predictive value of GTV in radiotherapy of NSCLC - early results of the NCT03055715 trial C. Ostheimer 1 , C. Baues 2 , R. Baumann 3 , C. Billiet 4 , S. Dobiasch 5 , N. Ebert 6 , D. Fleischmann 7 , T. Gauer 8 , Y. Goy 8 , J. Haussmann 9 , C. Henkenberens 10 , L. Kaessmann 11 , J. López guerra 12 , D. Kaul 13 , D. Krug 14 , M. Maeurer 15 , M. Niyazi 16 , M. Oertel 17 , C. Panje 18 , L. Sautter 19 , D. Schmitt 14 , C. Suess 20 , M. Trommer-Nestler 21 , S. Ziegler 22 , D. Medenwald 1 1 university hospital halle, department of radiation oncology, halle, germany 2 university hospital of cologne, department of radiotherapy, cologne, germany 3 university medical center schleswig-holstein, department of radiation oncology, kiel, germany 4 katholieke universiteit leuven, department of radiation oncology, antwerp, belgium 5 technische universität münchen, department of radiation oncology, munich, germany 6 university medical center dresden, department of radiation oncology, dresden, germany 7 lmu munich, department of radiation oncology, munich, germany 8 university medical center hamburg-eppendorf, department of radiotherapy and radio-oncology, hamburg, germany 9 university medical center düsseldorf, department of radiation oncology, düsseldorf, germany 10 hannover medical school, dept. Of radiation oncology, hannover, germany 11 university of schleswig-holstein- campus luebeck, department of radiation oncology, luebeck, germany 12 hospital universitario virgen del rocío, department of radiation oncology, sevilla, spain 13 charité school of medicine and university hospital, department of radiation oncology, berlin, germany 14 university hospital heidelberg and national center for radiation research in oncology ncro and heidelberg institute for radiation oncology hiro, department of radiation oncology, heidelberg, germany 15 university medical center jena, department of radiation oncology, jena, germany 16 lmu munich, department of radiation oncologz, munich, germany 17 university medical center muenster, department of radiation oncology, muenster, germany 18 kantonsspital st. gallen, department of radiation oncology, st. gallen, switzerland 19 university medical center mannheim, department of radiation oncology, mannheim, germany 20 university medical center regensburg, department of radiation oncology, regensburg, germany 21 university hospital of cologne, department of radiation oncology, cologne, germany 22 university medical center erlangen, department of radiation oncology, erlangen, germany Purpose or Objective In the radical radiochemotherapy (RCT) of inoperable non-small-cell lung cancer (NSCLC), typical prognostic factors include T- and N-stage while there is still uncertainty and conflicting data on the prognostic relevance of gross tumor volume (GTV) and particularly of its changes during RCT. The NCT03055715 trial of the youngDEGRO working group of the German Society of Radiation Oncology (DEGRO) evaluated the prognostic impact of GTV and its changes during RCT of NSCLC. This is to report the early results of the trial. Material and Methods At present (01/2018), a total of 20 university centers for Radiation Oncology from 4 different European countries (Germany, Switzerland, Spain, Belgium) participated in the study which currently enrolled n=322 patients with confirmed (biopsy), inoperable NSCLC in UICC stage III

A/B who received radical curative-intent RCT (≥60 Gy, normofractionated) between 2011 and 2013. Patient and disease data was collected anonymously via electronic case report forms and entered into the multi-institutional "Radplan-Bio” platform for central data analysis. GTV before RCT (initial planning CT, GTV1) and at 40-50 Gy (re-planning CT for radiation boost, GTV2) was delineated. Absolute GTV before/during RCT and relative GTV changes were correlated with overall survival as the primary endpoint. Hazard ratios (HR) of survival analysis were estimated by means of adjusted Cox regression models. Results GTV1 was a survival predictor in a model adjust ed for age, T-stage and chemotherapy resulting in a n estimated hazard ratio of 1.12 (95% CI: 1.02-1.22, p=0.01, n=210) per 100 ml. Considering both, GTV1 and GTV2, in one survival model of overall mortality, we found GTV2 (HR=1.8, 95% CI: 1.11-2.92, p=0.02, p=0.17, 89 observations) to be a stronger survival predictor than GTV1 (HR=0.81, 95% CI: 0.61-1.09, p=0.17). There was no evidence for a survival effect of the relative or absolute change between GTV1 and GTV2 (relative: HR=1.03; 0.92- 1.16, absolute: HR=0.97; 95% CI: 0.77- 1.24 per 100 ml). When the absolute change was dichotomized at the median, subjects with a low reduction had a significantly higher risk of death (HR= 1.7; 95% CI; 1.0-2.8, p=0.04). Again the relative dichotomized change was no significant survival predictor (p=0.9).The median survival time was 1.5 years (95% CI: 1.2-1.7). The GTV1 was found to have a mean of 160.1 ml (95%CI: 139.4-180.7) and the GTV2 of 113.6 ml (95% CI: 92.7-134.5), resulting in an estimated reduction of 59.7 ml (95%CI: 42.8-76.6, p< 0.001). Considering the relative change in the GTV, we found a higher chance of experiencing an infection-related event in subjects showing a stronger GTV decline (OR=3.0 per 10% decrease; 95% CI: 1.1-8.2, p=0.04). Conclusion First results of the trial indicate that independently of T- stage, the re-planning GTV during RCT is a significant and superior survival predictor compared to baseline GTV. Patients with a low absolute change in GTV show an inferior outcome after RCT. SP-0330 Science slam: Report back from ESTRO mobility grants biology: Development of a radiation induced liver damage model N. Melin 1 , D. Sànchez 2 , B. Petit 3 , E. Herman 4 , Y. Zimmer 4 , D. Candinas 2 , M.C. Vozenin 3 , D. Aebersold 4 , D. Stroka 2 1 University of Bern, Visceral and Transplantation Surgery / Radiation Oncology, Bern, Switzerland 2 University of Bern, Visceral and Transplantation Surgery, Bern, Switzerland 3 Centre Hospitalier Universitaire Vaudois, Radiation oncology, Lausanne, Switzerland 4 University of Bern, Radiation Oncology, Bern, Switzerland Abstract text In the last decades, technological advances have allowed powerful scientific discoveries. The profusion and accessibility of complex tools make it impossible for a single individual to use them all at their full potential. Collaborative effort has led to great advance in the radio oncology field. Yet liver cancer is still a challenge and the use of radiation is limited by the development of radiation induced liver disease (RILD). Aiming to understand the biological process leading to RILD, we have set up collaborations and engaged discussion with different research groups. The unique knowledge and expertise of each of those collaborators was catalyzed by my visit to the group of professor Guha in New York thanks to the mobility grant. Inspiring our self from the irradiation protocol developed by professor Guha his group for hepatic cell transplantation, we