ESTRO 38 Abstract book

S738 ESTRO 38

common acute toxicity was G1 fatigue (in 13 patients). The most frequently documented late side effect was G1 pneumonitis in 46 patients (followed by G1 dyspnea in 12, G1 thoracic pain in 11, and G1 cough in 10). Two ribs fractures occurred, and no toxicities greater than G3 were observed. Different fractionation schedules (including one-fraction) did not have an impact in OS, DSS or L-PFS, both in tumors ≤2cm, and in tumors ˃ 2cm, and no schedule exhibited a trend towards worse outcomes. Conclusion In our series, OS, DSS and L-PFS are in accordance with literature-reported outcomes. Although the low number of progressions may limit the analysis, one-fraction SBRT does not seem to be inferior to other fractionation schedules in appropriately selected patients. The low number of observed side effects (namely G≥3) also did not allow us to infer any correlation with the fractionation schedule. EP-1349 Three-d Surface Imaging as preferred tool for patients’ set up in frameless SBRT for lung cancer C.M.E. Perotti 1 , C. Pisani 1 , G. Loi 2 , A. Belli 1 , C. Bolchini 1 , Y. Huang 3 , J. Lyu 3 , M. Krengli 4 1 University Hospital "Maggiore della Carità", Department of Radiotherapy, Novara, Italy ; 2 University Hospital "Maggiore della Carità", Department of Medical Physics, Novara, Italy ; 3 Sichuan Cancer Center, Department of Radiation Oncology, Chengdu, China ; 4 University of "Piemonte Orientale"- University Hospital "Maggiore della Carità", Department of Translational Medicine- Department of Radiotherapy, Novara, Italy Purpose or Objective Surface-based image guided radiotherapy (IGRT) allows positioning and/or monitoring patients receiving radiation treatment in 3 dimensions (3D), without the use of ionizing radiation. The purpose of this study is to investigate the usage of 3D Surface Imaging, specifically the Vision RT's AlignRT system, as the primary tool for the set up of patients who are treated with frameless stereotactic body radiotherapy (SBRT) for lung cancer by comparison with cone-beam computed tomography (CBCT). Material and Methods Twenty patients (12 men and 8 women) were included in the study. For each fraction of treatment the patients were positioned using the AlignRT system and the vertical, longitudinal and lateral shifts were measured with the CBCT according the Cartesian axis system. Surfaces were captured just before CBCT acquisitions. The data were retrospectively retrieved, manually researching the medical records reporting the values of the shifts detected with CBCT. The mean, the range and the standard deviation relative to the shifts were calculated with respect to the X, Y and Z axes. The agreement between the two different procedures was then analyzed with the Bland-Altman test, which allows to evaluate the correlation between two systems that measure the same parameter. Results The mean of the shifts was found to be equal to -0.08 cm (range -0.3; 0.5) for the Z axis, equal to 0.01 cm (range - 0.7; 0.5) for the X axis and 0.04 cm ( range -0.8; 0.6) for the Y axis. The standard deviation was 0.21 cm for the Z axis, 0.22 cm for the Y axis and 0.23 cm for the X axis, respectively; these standard deviation values probably reflect the presence of some outliers values that are highly likely to represent data entry errors.

Conclusion Three - dimensional surface imaging is confirmed to be a reliable method for patients’ setup, able to guarantee high precision in the delivery of SBRT treatment. EP-1350 DART-bid by VMAT for locally advanced NSCLC: Low toxicity, encouraging survival and tumor control K. Wurstbauer 1 , R. Pinter 1 , M. Meinschad 2 , M. Kazil 1 , T. Hernler 3 , P. Cerkl 3 , T. Künzler 2 , A. De Vries 1 1 Academic Teaching Hospital, Radiation Oncology, Feldkirch, Austria ; 2 Academic Teaching Hospital, Medical Physics, Feldkirch, Austria ; 3 Academic Teaching Hospital, Pneumology, Hohenems, Austria Purpose or Objective Results of 60 Gy with concurrent chemotherapy for locally advanced NSCLC are disappointing. DART- bid (dose- Differentiated Accelerated RadioTherapy - 1,8 Gy twice daily) is a radiation dose-intensified approach, sequentially combined with chemotherapy. Our experience up to now is reported. Material and Methods 55 widely unselected patients (85% in stages IIIA-C, 8 th edition) were treated from 1/2015 until 5/2018. >5% weight loss/ 3 months in 31%, KI <80% in 24% of patients. Overall doses applied were as follows: Primary tumors 73.8 - 90.0 Gy, in positive correlation to tumor volumes; nodes 61.2 Gy; nodes electively 45 Gy (to sites about 6 cm cranial of macroscopically involved nodes); fractional doses 1.8 Gy bid; interval 8h. GTV (ITV) to PTV: 7 mm; planning with the intention to spare as much as possible of the ipsilateral (tumorbearing) lung; application by VMAT; cone beam CT before every fraction. Duration of radiotherapy 31 days median (28-37 days); in 89% of the patients 2 cycles platin-based chemotherapy were given before, with a target interval between chemotherapy and radiotherapy of < 8 days. Results With a median follow-up time of 12.6 months (3.9-37.5 m.) the 1-yearoverall survival rate is 72%, the median overall survival time 24.1 months; for the 21 patients (38%), matching with the RTOG 0617 inclusion criteria, the 1 year survival rate amounts to 78% and the median overall survival time is not reached. 7 local recurrences and 5 isolated regional recurrences occurred, resulting in local and regional tumor control rates at 1 year of 86% and 90%, respectively. Acute adverse effects of pneumonitis grade 2 and3 occurred in 4 and 1 patients, respectively; acute