ESTRO 37 Abstract book

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ESTRO 37

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 GTV1 was a survival predictor in a model adjusted for age, T-stage and chemotherapy resulting in an 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. models. Results

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 succeed to irradiated mice that locally developed RILD associated fibrosis. Bringing together multiple expert form radiation oncology, animal radiation, cell transplantation, bioinformatics, liver biology, we succeed to identify putative RILD marker should allow to better describe RILD mechanistic and further evaluation of prophylactic and therapeutic interventions. SP-0331 Science slam: Report back from ESTRO mobility grants physics: Modern dose calculation algorithms in brachytherapy G. Fonseca 1 , S.L. Thrower 2 , K. Gifford 2 , F. Verhaegen 1 1 GROW-School for Oncology and Developmental Biology- Maastricht University Medical Center, Department of Radiation Oncology MAASTRO, Maastricht, The Netherlands 2 The University of Texas MD Anderson Cancer Center, Department of Radiation Physics, Houston, USA To calculate and compare two commercially available Model Based Dose Calculation Algorithms (MBDCA) and Monte Carlo (MC) simulations for an APBI brachytherapy case. Methods Oncentra ® brachy ver. 4.5 ACE (Advanced Collapsed cone Engine, Elekta AB, Stockholm, Sweden), Acuros™ BV ver. 13 (Varian Medical Systems, Inc., Palo Alto, CA) and MCNP ver. 6.1.1 were used to calculate dose for an APBI brachytherapy case. The input for all calculations was a clinical APBI brachytherapy case with the SAVI ® (Cianna Medical, Aliso Viejo, CA) device. The HU to density calibration curve from ACE was used for all calculations. AMIGOBrachy was used to convert the patient CT geometry into voxels to generate the input deck for MCNP and to convert ACE files into the Acuros format. DVHs, target coverage (V 90 , V 95 , and V 100 ), highest dose to normal breast tissue (V 150 , V 200 ) and critical structure doses (dose to the highest 0.1 and 1.0 cc volume D 0.1cc , D 1cc for skin and rib) were compared. Dose ratios were also computed and compared amongst the algorithms. Results: Results obtained using a uniform water medium (Dose-to-water-in-water, D w,w ) demonstrate agreement within 1.1 ± 1.2% (mean difference ± one standard deviation) for all the methods. Isodoses indicate agreement better than 0.3 mm (Figure 1a). This is impressive considering that Varian and Nucletron/Elekta HDR source designs are slightly different. The agreement is slightly worse 2.0 ± 2.2% (mean difference ± one standard deviation) comparing dose-to-medium-in- medium (D m,m ). Here isodose differences (Figure 1b) are visible near tissue interfaces (≈1.2 mm shift of 75% isodose line proximal to the skin surface). Table 1 shows less the 1.1% difference between the commercial algorithms and MC for the clinical dose metrics in water (D w,w ). Clinical dose metrics obtained using D m,m show up to 8.4% difference between the commercial algorithms and MC and 4.3% difference between ACE and Acuros. Larger differences were observed for lung due to material misassignment as a significant volume of the lung was automatically assigned as air in the commercial system Abstract text Purpose