ESTRO 36 Abstract Book

S762 ESTRO 36 _______________________________________________________________________________________________

sinusoidal movement with changeable motion amplitude and frequency. To simulate target motion during a normal breathing to the sphere it was applied a movement of ± 5 mm in antero-posterior and lateral direction, ± 10 mm in superior-inferior direction. The frequency of respiratory cycles was set to 1 cycle/3 seconds. A planning CT of the CIRS phantom was performed using a 3 mm slice thickness. CT images were exported to the Oncentra Masterplan (OM) version 4.3. Planning target volume (PTV) was obtained by adding an isotropic expansion of 0.8 cm to sphere (gross tumor volume, GTV) delineated on CT “lung” window and without inclusion of blurring effect. A test VMAT treatment plan with identification of the isocenter at the center of the PTV was created. A verification of the target sphere position by means of Symmetry TM was performed. 4D-CBCT was acquired and subsequently sent to the OM to verify the correspondence between volumes planning CT- based and volumes obtained on CBCT 4D and to obtain ITV- 4D. GTVs were delineated on all phases of 4D-CBCT to define ITV. Results Simmetry XVI software appeared able to follow organ movements. It was found from this study that ITV4D-CBCT and PTV4D-CBCT were overlapped. The margin applied to obtain CTV was reliable. Conclusion The 4D-CBCT with Simmetry XVI was adequate in providing imaging-guidance for treatment of lung cancer and other tumors occurring in site influenced by organ motion. Simmetry XVI is a valid instrument to perform a respiratory-gated radiation therapy when 4D planning CT is not available. Actually, in our department, the applicability of this procedure on patients continues to be under investigation. EP-1427 Peer reviewed radiation treatment planning process at a university hospital in a developing country B.M. Qureshi 1 , A.N. Abbasi 1 , N. Ali 1 , A. Hafiz 1 , M.U. Karim 1 , A. Mansha 1 1 Aga Khan University Hospital, Radiation Oncology Section- Dept. of Oncology, Karachi, Pakistan Purpose or Objective The study aimed to evaluate if peer review in weekly simulation review meeting impacts the radiation therapy treatment planning process in a resource limited setting. Material and Methods The study was done at the Radiation Oncology facility of Aga Khan University, Karachi Pakistan for a period of 2 months. Simulation review meeting (SRM) was held weekly during the study to discuss all the patients being planned for radiation therapy in the presence of consultants and residents. Each patient's contour of organ at risk and treatment volumes or fields, total dose, dose per fraction, number of phases etc are discussed after being planned by primary radiation oncologist. In this study, data was recorded for patients being planned for radiation in weekly SRM in the presence of at least 2 radiation oncologist. Intent was recorded as radical or palliative and discussion for all the patients including 2-D, 3D-CRT and IMRT was noted. The study included patients of primary malignancies of different anatomic regions, treated with external beam radiation therapy at our institute except those who were planned and treated on the same day. Impact of peer reviewed SRM was recorded as 'no change', 'minor change' or major change in contour, dose, field size or intent of treatment. This data was recorded after approval of institutional ethical review committee. Results Data was collected for a total of 116 patients, out of which 96 we planned with radical intent and 20 for palliation. 61% patients were planned with 3D-CRT technique & 26%

with IMRT. Major primary sites included head and neck (40%), thorax (26%), pelvis (51%) and brain (12%). At least three radiation oncologists were present in two third meetings and changes were mostly made in with gross tumor volume or clinical target volume. It was observed that minor changes were made in 13% patients and major change was done in the plans of 9% of patients. Conclusion In this modern era of precision radiation therapy treatment planning, peer review of the planning process has a vital role. Peer review of treatment plans among radiation oncologist improves the process and recommended changes can be incorporated in the the treatment plans in a timely manner. The study shows that the review of treatment plans is a necessary quality step in radiation therapy and can be done on a weekly basis for all the patients. Hence, the quality of planning is improved in a resource limited university hospital. EP-1428 Stereotactic body radiotherapy for isolated metastasis from different primitive tumors A. Lancia 1 , G. Ingrosso 1 , A. Carosi 1 , L. Di Murro 1 , E. Giudice 1 , S. Cicchetti 1 , P. Morelli 1 , C. Bruni 1 , D. Di Cristino 1 , A. Murgia 1 , A. Cancelli 1 , I. Turturici 1 , A. Iadevaia 1 , R. Santoni 1 1 Tor Vergata University Hospital, Department of Diagnostic Imaging- Molecular Imaging- Interventional Radiology and Radiotherapy, Roma, Italy Purpose or Objective The oligometastatic state identifies a subset of patients who might be amenable to curative therapy. In this specific group of patients, Stereotactic Body Radiation Therapy (SBRT) has been shown to reach high levels of local tumor control through the delivery of high doses of radiation in few fractions, without the development of significant toxicity. Any meaningful improvement in survival remains debatable. Material and Methods From July 2007 to March 2016, 78 patients were treated at our Department with Stereotactic Radiotherapy for isolated body metastasis. The most frequent primary tumor was prostate cancer (28.2%), followed by colorectal cancer (23.1%), and lung cancer (20.5%). All patients received a radical treatment to the primary tumor site . Median time from primary tumor treatment to SBRT for oligometastatic disease was 30.3 months (range 1.07- 232.3). No patient had synchronous metastases at the time of SBRT. Median age at diagnosis of oligometastatic disease was 70 years (range 47-88). Median Karnofsky Performance Status (KPS) was 90 (range 70-100). Patients were also evaluated in terms of Charlson Comorbidity Score (CCS). The most used SBRT dose fractionation scheme was 35 Gy in 5 fractions. Overall Survival (OS), Cancer-Specific Survival (CSS), and Local Control (LC) were calculated from the end date of SBRT to the end of follow-up; Progression-Free Survival (PFS) was calculated from the end date of SBRT to the first clinical progression. Treatment related toxicity was evaluated using the CTCAE version 4.0. Results Median follow-up was 22.68 months (range 1.9-95.73). One year and 2 years LC were 91% and 89%, respectively. At the time of analysis, thirty-one patients (39.7%) were free from local and systemic progression: one and 2-year PFS were 85% and 72%, respectively. CSS at one year was 93% and it was 85% at two years. One and 2-year OS were 92% and 82%, respectively . At the univariate analysis, we found that KPS ≥ 80 was a statistically significant prognostic factor for OS, and PFS (p=0.001 for both). OS was also influenced by the primitive tumor (p=0.006). 8