ESTRO 37 Abstract book

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ESTRO 37

and mean dose <26Gy, mean dose to liver <30Gy, volume of ipsi-lateral kidney receiving 30Gy (V30Gy<50%), dose to 0.1cc of esophagus <55Gy, spinal cord <50Gy, small bowel <45Gy and stomach <45Gy. Results Bulky target volume coverage was achieved by normalisation in each case. Both plan types were able to achieve OAR objectives for lung V20Gy and mean lung dose, mean heart dose, volume of ipsi-lateral kidney receiving 30Gy, dose to 0.1cc of oesophagus, spinal cord and small bowel on all occasions. P_ HYB did not meet lung V5Gy for any plan (88.2-99.4%), whereas P_ TO met in each case (68.3- 74.8%). P_ HYB met heart V35Gy on 5 occasions (25.2- 37.3%), however P_ TO met in all plans (24.6-35.0%). In two patients the dose to 0.1cc of the stomach failed for P_ HYB (0-51Gy), however this constraint passed on all occasions for P_ TO (0-43.3Gy). Reductions in OAR doses were observed when using the P_ TO plan in comparison to plans calculated without Trade-Offs. Utilising this new calculation method allowed all patients to have a clinically acceptable radical plan. Conclusion Trade-Offs planning provides improvements in OAR sparing when compared with hybrid IMRT/VMAT alone. The coverage of the PTV was comparable. The addition of multi criteria optimization provides improvements in plan quality that meet all pre-defined clinical objectives. EP-1409 Changes in pulmonary-function-test and toxicity evaluation after SBRT in early-stage NSCLC C. Cigarral García 1 , A. Matías Pérez 1 , J. Ramos González 2 , M. Saez Beltrán 3 , B. Cigarral García 4 , O. Alonso Rodríguez 1 , P. Soria Carreras 1 , M.T. Gómez Hernández 5 , L.A. Pérez Romasanta 1 1 Hospital Clínico Universitario de Salamanca, Radiation Oncology Department, Salamanca, Spain 2 Hospital Clínico Universitario de Salamanca, Pneumology Department, Salamanca, Spain 3 Hospital Clínico Universitario de Salamanca, Medical Physics Department, Salamanca, Spain 4 Hospital Clínico Universitario de Salamanca, Medical Oncology Department, Salamanca, Spain 5 Hospital Clínico Universitario de Salamanca, Thoracic Surgery Department, Salamanca, Spain Purpose or Objective Stereotactic body radiation therapy (SBRT) is the standard of care for patients with inoperable early-stage non-small cell lung cancer (NSCLC) or for those who refuse surgery. Most of these patients have advanced age and have different comorbidities such as moderate- severe chronic obstructive pulmonary disease (COPD) or vascular disease. The objective is to evaluate pulmonary- function-test (PFTs) changes and toxicity after lung SBRT. Material and Methods From June-2012 to October-2016, seventy-two patients with early-stage NSCLC were prospectively included in the study. Mean age was 72 years old (range 48–87). PFTs included forced expiratory vital capacity (FVC), forced expiratory volume in 1 second (FEV1) and carbon monoxide diffusion capacity (DLCO c ) by the single-breath method. These parameters were measured at baseline and evaluated 1.5-months after SBRT and annually thereafter. Toxicity assessment was performed during and after SBRT according to CTCAE v4.0. Statistical analysis was performed with IBM® SPSS Statistics V.23.0 software. Results Median follow-up was 24 months (range 10-62). Asthenia Grade (G) 1-2 was the most common acute toxicity (19 patients [27%]). Acute radiation-induced pneumonitis G3 ocurred in 3 cases (4%) and was not increased among patients with lower PFTs. Chronic toxicity G1 was reported in 20 patients (27%), being radiation-induced

Purpose or Objective Chest wall (CW) pain is a recognized late complication of stereotactic body radiotherapy (SBRT) to the lung. Despite multiple retrospective case series investigating the influence of dose volumes histogram (DVH) metrics and CW pain, there remains no clear consensus on what the constraints should be. Furthermore, differing dose and fractionation schedules could influence the incidence of the pain and interpretation of these metrics. Our aim is to report on the incidence and predictive variables of chest wall pain following lung SBRT with the same dose and fractionation in a single institution. Material and Methods Clinical, tumour and dosimetric parameters were collated and analysed in patients treated with lung SBRT with 48Gy in 3 fractions. Toxicity was graded by two physicians according to Common Terminology Criteria for Adverse Events v3.0. Results A total of 135 number of patients were treated between 2007 and 2016 with a median follow up of 20 months. A total of 12/135 (9%) patients developed CW pain, of whom 8 (6%) had grade 1, 3 (2%) had grade 2, 1 (0.7%) had grade 3 reactions. Univariate analysis demonstrated that V30, V40, V50 and PTV volume significantly predicted chest wall pain but were later proved non- significant on multi-variate calculations. Dosimetric variables such as D1cc, D2cc, D5cc and overlap volume as well as clinical parameters such as age, osteoporosis and diabetes all failed to show significance. Conclusion CW pain is an important late toxicity causing significant morbidity following lung SBRT in certain subsets of patients. Our analysis could not find significant correlations between any of the DVH variables and the incidence of CW pain. Further multi-institutional analysis is required to develop clearer dosimetric constraints. EP-1408 An investigation of hybrid planning with multi criteria optimization for mesothelioma T. Mitchell 1 , A. Cascales 1 , W. Poon 1 , R. Valentine 1 , S. Currie 1 , S. Harrow 1 1 Beatson Cancer Center, Clinical Oncology, Glasgow, United Kingdom Purpose or Objective To evaluate the treatment plan quality produced by two treatment planning approaches for mesothelioma; the use of hybrid IMRT and VMAT techniques, with and without multi-criteria optimization (Trade-Offs). Material and Methods Seven palliative patients, previously treated as part of the System Clinical trial were planned retrospectively using Eclipse TPS v15.5 [Varian Medical Systems, Palo Alto, CA, USA] with a hybrid IMRT-VMAT plan. This consisted of either a 2 or 4 field parallel opposed IMRT plan combined with two VMAT fields (P_ HYB ). These plans were then optimised with Trade-Offs (P_ TO ), a multi- criteria optimisation planning method available in Eclipse v15.5. This cohort of patients had extensive disease with one of either lungs included within the PTV. The bulky PTV was prescribed to receive 55Gy in 25 fractions and the remaining pleural cavity of the involved lung treated to 45Gy in 25 fractions. Individual PTV volumes varied from 764 to 4924cc. Plans consisted of up to three isocentres and were normalized to ensure that 95% of the bulky PTV received 95% of the prescribed dose. Additional, Trade- Off optimisation was applied to both the IMRT and VMAT plans creating a second hybrid plan that was normalised by the same method. Plan quality was evaluated by: volume of the lung receiving 5Gy (V5Gy<75%), 20Gy (V20Gy<10%) and a mean dose <10%, volume of heart receiving 35Gy (V35Gy<35%)