ESTRO 37 Abstract book

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ESTRO 37

the PTV-volumes (Δvolume) and the dose change (Δdose), as well as between the 3D movements and Δdose are listed in Table 2 (p<0.01). The 3D movement shows stronger correlations with the Δdose (0.74-0.80) than with Δvolume (0.48-0.62).

Conclusion This study suggested that patients with emphysema were less subject to RILT. In addition, RILT was better associated with FLV exposure than total lung exposure. Therefore a FTP would be desirable, but it’s limited to a small number of cases depending on PE amount and distribution. EP-1389 Reduction of lung dose during stereotactic radiation of lung tumors using respiratory gating A. Hofmeister 1,2 , M.N. Duma 1,3 , M. Wiegandt 1,2 , S.E. Combs 1,3 , J.J. Wilkens 1,3 , M. Oechsner 1 1 Klinikum rechts der Isar - Technische Universität München, Klinik und Poliklinik für RadioOnkologie und Strahlentherapie, München, Germany 2 Technische Universität München, Fakultät für Medizin, München, Germany 3 Helmholtz Zentrum München, Institut für Innovative Radiotherapie iRT, München, Germany Purpose or Objective Stereotacic body radiotherapy (SBRT) is a well- established treatment option for lung cancer. Respiratory gating (RG) enables dose reduction to organs at risk (OARs). In this study, the possible dose reduction of the lung, thoracic wall and heart during lung SBRT, employing RG during inspiration and expiration was examined. Additionally, factors that influence the dose reduction were determined. Material and Methods 49 lung SBRT patients were retrospectively selected. All patients underwent 4D-CT scanning, consisting of 10 phase CTs representing the breathing cycle. Three radiation windows were determined per patient: Free breathing (all 10 phases), inspiration (phases 90%, 0%, 10%), and expiration (phases 40%, 50%, 60%). The gross tumor volume (GTV) was contoured in all 4DCT phases. Internal target volumes (ITVs) were determined for all three radiation windows by combining the GTVs of each respective phase. PTVs were generated by adding a 5 mm safety margin. Volumetric modulated arc therapy (VMAT) plans were calculated using prescription doses of 3x15Gy (PTV<65.5ccm) or 5x8Gy (PTV>65.5ccm) surrounding 98% of the PTV. Doses to the lung and the heart were examined. PTV volumes and 3D movements of the tumors were determined as well. Statistical analysis were performed using the Wilcoxon-Test and Spearman´s correlation coefficient. Results The results are listed in Table 1 including the median (min-max). The lung dose for Dmean and V20 is significantly higher in free breathing than with respiratory gating in inspiration and expiration (p<0.01). The lung dose is slightly lower in inspiration than in expiration, however, not significantly (p>0.05). The mean heart dose was significantly lower in expiration than in free breathing and inspiration for tumors located cranial of the heart; for those located caudal it was lower in inspiration. The correlation coefficients between the difference of

Conclusion According to the results, using respiratory gating for lung SBRT enables significant dose reductions of lung tissue as well in inspiration as in expiration. However, it is not possible to conclude which phase is better, because there is no significant difference. There are significant correlations between the Δvolume or the 3D movement of the tumors and the dose reduction of the lung. A strong dose reduction is awaited for tumors whose PTVs are highly minimized through inspiratory or expiratory gating windows. As well as for tumors with a large 3D movement. Our findings show that tumors located close to the cranial part of the heart benefit from an expiratory and those located caudal from an inspiratory gating window. Individual testing of the craniocaudal position in relation to the heart is recommended. hypofractionated tomotherapy for progressive MPM in patients with intact lungs A. Fodor 1 , S. Broggi 2 , E. Incerti 3 , I. Dell'Oca 1 , C. Fiorino 2 , A.M. Samanes Gajate 3 , P. Passoni 1 , M. Pasetti 1 , M.G. Cattaneo 2 , L. Gianolli 3 , R. Calandrino 2 , M. Picchio 3 , N.G. Di Muzio 1 1 San Raffaele Scientific Institute, Department of Radiotherapy, Milano, Italy 2 San Raffaele Scientific Institute, Medical Physics, Milano, Italy 3 San Raffaele Scientific Institute, Department of Nuclear Medicine, Milano, Italy Purpose or Objective Adjuvant IMRT after Pleurectomy/Decortication(P/D), in pts with intact lungs, is to be considered according NCCN guidelines. The aim of this study was to present the outcome of our protocol of salvage moderately hypofractionated tomotherapy (HTT) with/without simultaneous integrated boost (SIB) on FDG-PET positive areas (BTV), for pts with progressive Malignant Pleural Mesothelioma after previous treatments (chemotherapy+/- surgery), and intact lungs Material and Methods From May 2006- April 2014, 51 pts (41 men and 10 women, left pleura: 25, right: 26) with median age 68.8 (38.6-82.0) years, were treated. Histology: epithelioid in 43, sarcomatoid in 8 pts. Initial stage was: I -11 pts, II -14 pts, III -17 pts and IV -9 pts. Chemotherapy up to 6 cycles was prescribed for 33 pts, and for 13 more than 6 cycles. Eighteen pts had P/D and 33 talc pleurodhesis. A total dose of 56 Gy/ 25 fr to the whole pleura was delivered to all pts, with SIB to 62.5 Gy on PET positive volumes in 38 pts. V5, 10 and 20 of contralateral lung were reduced as low as possible, resulting in a median value for D mean <6.9 Gy. Results Median survival from diagnosis was 25.8 (8.4-99.0) months: 5.9 (1.2-50.5) months from the beginning of HTT EP-1390 Salvage (postponed)