Abstract book - ESTRO meets Asia

S3 ESTRO meets Asia 2018

SP-010 How to deal with nodal involvement in OPC V. Gregoire 1 1 Centre Léon Bérard Radiation Oncology, Lyon, France

and 2 year PFS were 72 and 27%, 55 and 21%, 46 and 13% respectively in the three treatment techniques (p < 0.001). The toxicities assessed were similar in both IMRT and VMAT. The prognostic factors found to be influencing the treatment outcomes included age, gender, grade of tumor and Karnofsky performance status (KPS) of the patient. Conclusion The treatment outcomes in the form of overall survival and toxicities are found to be better with VMAT and also to spare the normal brain parenchyma and structures at risk. With modern treatment techniques available to permit better tumor dose conformity and spare normal tissue, outcomes of the disease can be achieved in desirable manners. VMAT is an excellent technique for treatment of high grade gliomas and needs to be looked in to in future large prospective trials. OC-013 Dosimetric comparison of breath hold and free breathing technique in stereotactic body radiotherapy K.R. Mani 1 , R. Lingaiah 1 , M.M. Alam 1 , M.A. Bhuiyan 1 , K.A. Haque 1 , S. Ahmed 1 , M.A. Sumon 1 , S. Basu 1 , A.K. Sengupta 1 , M.R.U. Nabi 1 , S. Chadhuri 1 1 UNITED HOSPITAL LTD, Radiation Oncology, Dhaka, Bangladesh Purpose or Objective To compare the dosimetric advantage of stereotactic body radiotherapy (SBRT) for localized lung tumor between deep inspiration breath hold technique and free breathing technique. Material and Methods We retrospectively included ten previously treated lung tumor patients in this dosimetric study. All the ten patients under went CT simulation using 4D-CT free breathing (FB) and deep inspiration breath hold (DIBH) techniques. Plans were created using three coplanar full modulated arc using 6 MV flattening filter free (FFF) bream with a dose rate of 1400 MU/min. Same dose constraints for the target and the critical structures for a particular patient were used during the plan optimization process in DIBH and FB datasets. We intend to deliver 50 Gy in 5 fractions for all the patients. For standardization, all the plans were normalized at target mean of the planning target volume (PTV). Doses to the critical structures and targets were recorded from the dose volume histogram for evaluation. Figure 1 Illustrate the dose distribution in DIBH & FB scan, which clearly describes the target volume reduction and lung expansion in the DIBH technique compared to the FB technique Results The mean right and left lung volumes were inflated by 1.55 and 1.60 times in DIBH scans compared to the FB scans. The mean internal target volume (ITV) increased in the FB datasets by 1.45 times compared to the DIBH data sets. The mean dose followed by standard deviation (x̄ ± s x̄ ) of ipsilateral lung for DIBH-SBRT and FB-SBRT plans were 7.48 ± 3.57 (Gy) and 10.23 ± 4.58 (Gy) respectively, with a mean reduction of 36.84% in DIBH-SBRT plans. Ipsilateral lung were reduced to 36.84% in DIBH plans compared to FB plans. We found that the increase in the PTV volume in the FB-SBRT compare to the DIBH-SBRT, FB- SBRT resulted in the higher dose to the lung and the critical structures. In DIBH-SBRT the mean heart dose was reduced by 11.98% and V20 by 28.31% (both the mean dose and V20 shows statistical significance) compare to the FB- SBRT. Ipsilateral lung for the DIBH-SBRT plans shows a mean reduction of 36.84% in mean dose, 46.21% in V20 and

Abstract not received

Teaching lecture: Cell survival and models – intro to LQ

SP-011 Cell survival and models – intro to LQ M. Joiner 1 1 Wayne State University, Academic Physics, Detroit, USA

Abstract not received

Proffered papers: doseplanning and verification (physics) OC-012 Analysis of Newer Treatment Techniques in High Grade Glioma: VMAT Versus IMRT Versus 3DCRT V. Pareek 1 , R. Bhalavat 1 , M. Chandra 1 , P. Bauskar 1 1 Jupiter Hospital, Radiation Oncology, Mumbai, India Purpose or Objective In high grade gliomas, clinical outcomes depend on the tumor dose coverage and toxicities depends on the dose to surrounding organs at risk. With advent of newer modalities in the form of Intensity Modulated Radiation Therapy (IMRT) and VMAT, there is a need to look in to the dosimetric and clinical outcomes compared to the standard 3D conformal radiation therapy (3DCRT). This study, aims to evaluate the dosimetric and survival outcomes with respect to tumor doses and normal organs at risk and form a consensus on better treatment modality. Material and Methods Between 2011 and 2016, total 140 patients were evaluated of which 110 were WHO Grade IV and 30 patients were Grade III. Of these, 45 patients each underwent radiation therapy with VMAT and IMRT and 50 patients underwent 3DCRT treatment. The patients received 50.4Gy followed by boost of 9Gy with 1.8Gy per fraction dose. Planning was done with the aim of 98% of PTV covered by 95% isodose. Mean OAR dose were maximally decreased without reducing PTV coverage or violating hotspot constraint. The treatment plans were evaluated using standard dose volume histogram. The median follow-up of the patients was 13 months. The local control, overall survival and progression free survival were evaluated. Response was recorded using the Response Assessment in Neuro- Oncology criteria and toxicities graded according to CTCAE version 4.0. The dosimetric parameters were assessed using unpaired t test and the Wilcoxon matched-pair signed-rank test for non-parametrically distributed data used to compare the means. Maximum and mean OAR doses were directly used as part of the optimization process and, along with MU and timing, were considered as primary endpoints. Results All three techniques achieved an adequate dose conformity to the target volume. The conformity and Homogeneity index were found to be better with IMRT and VMAT (p < 0.005). The monitor units (MU) and treatment times were better with VMAT (p < 0.01). The doses to brainstem, optic nerve, retina, lens and normal brain parenchyma were found to be significantly better with VMAT. The median overall survival with VMAT, IMRT and 3DCRT were 16, 13 and 10 months respectively. The 1 year