Abstract book - ESTRO meets Asia

S129 ESTRO meets Asia 2018

Material and Methods Human cervix carcinoma HeLa cells were cultured with Bi 2 O 3 nanoparticles coated with 0.01, 0.5, 0.15 and 0.2 mMol of PEG and were irradiated with 6 and 10 MV photon beam with dose ranging from 0 to 10 Gy. The core size of uncoated Bi 2 O 3 nanoparticles was 60 nm with concentration of 0.5 µMol. The post-irradiation cells survival were evaluated using clonogenic assay and the dose enhancement factor (DEF) were calculated from the cell survival curves. Results The DEF for uncoated Bi 2 O 3 nanoparticles are 2.23 and Bi 2 O 3 -PEG nanoparticles coated with 0.01, 0.5, 0.15 and 0.2 mMol of PEG produce DEF of 1.65, 2.16, 1.97 and 1.68 respectively for 6 MV photon beams. Irradiation with 10 MV photon beam observe DEF of 1.95 for uncoated Bi 2 O 3 nanoparticles while for Bi 2 O 3 -PEG nanoparticles, the DEF varied with value of 0.95, 0.97, 0.96 and 1.02 respectively for each PEG concentration. Conclusion Bi 2 O 3 nanoparticles coated with PEG were observed to induce less dose enhancement effect in comparison to uncoated Bi 2 O 3 nanoparticles. Bi 2 O 3 nanoparticles are found to effectively induce dose enhancement but coating with PEG might reduce its therapeutic efficacy especially at high energy photon. PO-313 Retrospective Analysis of TCP-NTCP for Prostate Cancer using Niemierko based Radio biological Model P.K. Mani 1 , S. Paulpandi 1 , K. Bayyagari Reddy 1 , N. Veeraragavan 1 , V. Manoor Ural 1 1 Apollo Hospital, Radiation Oncology, Bangalore, India Purpose or Objective A radio biological model characteristically converts a physical quantity into a biological quantity thus the outcome of radiation treatments can be predicted earlier which enables, ensures the reliability and confidence on advanced treatment deliveries for better clinical outcome. In this study, Niemierko EUD based radio biological model was employed for the prediction of TCP and NTCP, to evaluate the sensitivity and effectiveness treatment for prostate cancers. Material and Methods A total of 15 prostate VMAT treatment plans were generated with dose of 79.2 Gy in 44 fraction to deliver to PTV - prostate and seminal vesicles with 3 mm margin. The plans were generated with Eclipse (V11.0) by meeting the RTOG dose constraints. TCP for tumor & NTCP for bladder, rectum and femoral heads have been calculated for all treatment plans using Niemierko EUD model. For TCP and NTCP calculation MS Excel architecture-based file enabled with Macros working environment was employed which converts DVH files as input for carrying the calculations. Quantitative measurements of dose-endpoint values on the dose-volume histograms were carried out for evaluation of dose homogeneity (D5% - D95%), degree of conformity (CI95%) and Quality of plan. Results The results of TCP calculated based on I MEAN and Niemierko’s EUD model for prostate VMAT plans, inferred an average predicted TCP of 98% which is fairly enough for control over disease. TCP calculated from Mean dose to the PTV and Niemierko based EUD calculations showed and good agreement with very minimal deviation less than 0.1%. In routine clinical conditions Mean dose can be used for calculating TCP for prostate cancers. The results of NTCP calculated for Bladder, Rectum and Femoral Heads normal tissue tolerance doses, in terms of TD5/5 and TD50/5, It is noted that for critical organs like bladder and femoral head there is lesser complication probability. A complication prediction of around 40% increase is observed for rectum.

Conclusion Over the past decades there have been several attempts to develop mathematical models for TCP and NTCP. The complexity and computer skills required by some of these models often alienate clinicians from this area of research. Many of these models have been used primarily as research tools. Clinical validation and clinical use of most of these mathematical models is essential. Mathematical models based on retrospective data that correlate with clinical outcome exist for specific organs. Even there have been few attempts to correlate NTCPs to actual treatment complications, and number of these have comprised retrospective analyses from patient histories and anecdotal evidence from physicians. Radiation Oncologists now want to take advantage of the latest technological developments in radiation therapy like VMAT to increase radiation doses without causing excessive side effects, it was timely to see if TCP/NTCPs could have greater application than just that of treatment plan ranking. PO-314 Impact on the use of heterogeneous phantom in pretreatment verification for VMAT of lung cancer H.S. Won 1 , K.Y. Eom 1 , J.B. Chung 1 , M.S. Han 2 , C.S. Park 3 , H.S. Lee 4 , S.S. Lee 4 , D.G. H Wang 4 1 Seoul National University Bundang Hospital, Radiation Oncology, Seongnam-si, Korea Republic of 2 Kangwon National University, Radiological Science, Samcheok-si, Korea Republic of 3 Hallym Polytechnic University, Radiological Science, Chuncheon-si, Korea Republic of 4 Sangji University, Biomedical Engineering, Wonju-si, Korea Republic of Purpose or Objective The Acuros XB (AXB) algorithm can predict the accurate dose on treatment plan for the lung and head and neck cancer, including many heterogeneous regions in the human body. Because the predicted treatment plan is a very complex and sophisticated treatment, it is necessary to verify whether the treatment plan is well implemented through patient specific-quality assurance (QA) before first treatment. Depending on the situations of the institution, various QA methods and phantoms are used to perform the patient-specific QA for treatment plan. In addition, the shape and material of the used QA phantoms are very diverse. However, most of QA phantoms configured a single material such acryl, plastic, and solid water, with a uniform density. Therefore, the purpose of this study was to investigate impact on QA phantoms designed the different material to verify the accuracy of dose distribution for volumetric modulated arc radiotherapy (VMAT) using AXB algorithm. Material and Methods The homogeneous and heterogeneous QA phantoms are developed to compare the pre-treatment verification according to the different materials of the phantom for routine VMAT of lung cancer. These phantoms are quadrature rectangular shape of horizontal 300 mm and vertical 315 mm length with inserts of various slabs. The homogeneous QA phantom was constructed using only polymethyl methacrylate (=1.19 g/cm 3 ). Another heterogeneous QA phantom was used a ceramic fiber board (=0.3 g/cm 3 ) modeled on similarly actual lung in human thorax. A total of 20 patients treated with VMAT technique for lung cancer were retrospectively selected for this study. All plans used one or two arc arrangements to get the optimal target coverage and were generated by the Eclipse treatment planning systems with the TrueBeamSTx accelerator. The calculated dose distributions were compared with the 2D dose distributions measured at the isocenter center position in RTT: Treatment verification