ESTRO 2020 Abstract book

S574 ESTRO 2020

Figure 2 shows the corrected Kaplan-Meier plot of overall survival in the validation dataset where a significant difference is seen between patients with a region dose above or below 16.2Gy, with a high dose to the region resulting in worse outcome.

PO-0992 Pericardial effusion after radiotherapy for Non-Small Cell Lung Cancer C. Linthorst 1 , R. Wijsman 2 , M. Fernandes 1 , S. Barbara 3 , J. Teuwen 4 , D. Bosboom 4 , R. Monshouwer 1 , J. Bussink 1 1 Radboud University Medical Center, Radiation Oncology, Nijmegen, The Netherlands ; 2 UMCG, Radiation Oncology, Groningen, The Netherlands ; 3 Netherlands Cancer Institute, Department of Radiation Oncology, Amsterdam, The Netherlands ; 4 Radboud University Medical Center, Radiology and Nuclear Medicine, Nijmegen, The Netherlands Purpose or Objective In locoregionally advanced Non-Small Cell Lung Cancer (LA- NSCLC) patients treated with radiation therapy, higher mean cardiac dose is associated with more grade 3 cardiotoxicity. Higher cardiac dose is also associated with a higher incidence of pericardial effusion. According to literature, up to 45% of the patients have pericardial effusion in the first two years after radiation therapy for LA- NSCLC. Importantly, higher cardiac dose, and even limited pericardial effusion is related to a detrimental outcome. At the moment, it remains unclear which patients are at risk for developing pericardial effusion and cardiac events. The aim of this study was to investigate associations between cardiac dose, clinical and radiological pericardial effusion and clinical outcomes in patients treated with (chemo-) radiotherapy for NSCLC. Material and Methods Patients with stage III NSCLC treated in our institution between 2008-2017 with IMRT of VMAT radiation therapy (60-66Gy in 2Gy fractions) with follow-up (FU) CT scans were analyzed. Pericardial effusion was assessed on the planning and follow-up CT scans, using the radiological report and Common Terminology Criteria for Adverse Events (CTCAE) v4.0 criteria. Additionally, pericardial thickness was quantitatively assessed on pre- and post- treatment CT scans by measuring the pericardial thickness at 3 predefined sites along the left and right ventricle and left atrium. Dosimetric data of heart and cardiac substructures, assessing atria and ventricles separately and combined, were obtained from the dose volume histograms. Patient records were reviewed for the clinical outcomes, including cardiac events, overall survival and disease free survival. Spearman’s correlations were calculated to analyse associations between cardiac dose, pericardial effusion and cardiac events. Results A total of 105 patients were analyzed, follow-up time ranged from 1 to 10 years. Of these patients 29 (27.6%) had a cardiac history, most frequently myocardial infarction, followed by angina pectoris. One patient had previously diagnosed pericarditis. In FU, 13 Patients (12.4%) had pericardial effusion according to the radiological reports. Cardiac events were present in 17 (16.2%) of patients in FU. Further results will be presented. Figure one shows the CT images prior to chemoradiotherapy (66Gy at 2Gy/fraction combined with 2 courses of PE) and one year after treatment. The images clearly shows substatiol developmet of pericardiall effusion still present at one year after treatment. Conclusion In this retrospective study we detected a substantial proportion of patients with pericardial effusion after radiotherapy for stage III NSCLC. Associations between cardiac dose, clinical and radiological pericardial effusion, along with the full dosimetric analysis, will be presented. PO-0993 Multicenter study of stereotactic body radiotherapy in non-small cell lung cancer (KROG 17- 09) S. Park 1 , J.H. Kim 1 , Y.C. Ahn 2 , J.M. Noh 2 , W.C. Kim 3 , M.K. Kang 4 , J.H. Cho 5 , J.S. Kim 6 , M. Kong 7 , J.W. Yea 8 , Y.S. Kim 9 , K.H. Choi 9 , S.G. Yeo 10

Conclusion This study suggests the relation between residual setup errors and survival could be explained by changes in cardiac dose. It identifies an area at the heart base where dose is correlated with survival. Our results suggest the dose threshold for cardiac damage is between 16.2–23.4Gy in the base of the heart, which was validated in an independent cohort. This study provides further evidence supporting the use of stricter heart dose constraints, and explores what these constraints should be. The dose effect in other regions of the heart should also be investigated.