ESTRO 2022 - Abstract Book

S1251

Abstract book

ESTRO 2022

tolerated. The data supports the use of SARS-CoV-2 vaccination in patients undergoing localized radiotherapy alone. For concomitant RT and ChT more data are needed.

PO-1474 Lower FDG PET/C Т SUV max shows better response to SBRT of adrenals in oligometastatic disease

K. Zhelev 1 , D. Katsarov 2 , N. Velikova 3 , Z. Zahariev 4 , I. Mihaylova 2 , N. Nedev 3 , R. Krasteva 5 , R. Hadgiev 6 , N. Conev 7 , I. Donev 8

1 MHAT Uni Hospital, Department of Radiotherapy, Panagyurishte, Bulgaria; 2 SHAT in Oncology Sofia, Department of Radiotherapy, Sofia, Bulgaria; 3 UMHAT Acibadem City Clinic, Department of Radiotherapy, Sofia, Bulgaria; 4 MHAT Uni Hospital, Deprtment of Radiotherapy, Panagyurishte, Bulgaria; 5 MHAT Uni Hospital, Department of Oncology, Panagyurishte, Bulgaria; 6 UMHAT Lozenetz, Department of Forensic Medicine , Sofia, Bulgaria; 7 UMHAT St Marina, Department of Oncology, Varna, Bulgaria; 8 MHAT Nadezhda, Department of Oncology, Sofia, Bulgaria Purpose or Objective Stereotactic body radiotherapy (SBRT), as ablative and noninvasive treatment was well established for oligometastatic disease (1 to 3 metastatic lesions) and became increasingly used to manage cancer with adrenal gland metastases. The aim of this multicentric study was to evaluate the safety and efficacy of SBRT in patients with oligometastatic disease in adrenal glands. Materials and Methods In this retrospective study, we performed an analysis of 75 metastatic adrenal lesions in 64 patients, where 36 (48%) non - small cell lung cancer (NSCLC), 18 (24%) small cell lung cancer (SCLC), 10 (13.3%) rectal cancer and other 11 (14.6%) (such as breast and renal cancer) oligometastatic disease, treated from 2015 to 2020, aiming to achieve durable local control. All patients progressed mainly with increasing adrenal masses area (other lesions were under control). Patients were divided into three groups according to their fluorodeoxyglucose positron emission tomography (FDG PET/C Т ) SUV max of adrenal metastasis – with low (up to 33th percentile, range: 3.9-7.20), intermediate (between 33th and 66th percentile, range: 7.21-9.31) and high SUV max (over 66th percentile, range: 9.31-25.8). Overall response rate (ORR), is the proportion of patients who had a partial or complete response to the treatment. The main dose regimens were 38 Gy delivered in 1– 5 fractions, with the median dose of primary tumor volume (PTV) being 38 Gy (range: 16–48 Gy) and the biologically effective dose (BED10, alpha/beta = 10) being 79.2 Gy (range: 41.6–105.6 Gy). Results The cohort included 34 men (53.1%) and 30 women (46.9%), with a total mean age of 65.5 ±8.9 years. ORR was 40%. Between all clinicopathological characteristic such as gender, age, histology, time to progression etc. we found no significant relationship except for levels of SUV max and ORR (Kendall Tau-c=0.29; p=0.017). Patients who responded to SBRT had a significantly lower SUV max value, than those who did not respond (7.6±2.4 vs 9.7±3.8; p=0.015). At the optimal cut-off values for SUV max, the biomarker could significantly and moderately distinguish between patients with or without response (AUC = 0.67, 95% confidence interval (CI) = 0.54–0.79; p = 0.015), with a sensitivity of 63.5% and a specificity of 60.1%. Moreover, in multiple binary logistic regression, lower levels of SUV max is associated with good response to radiotherapy (OR 0.27 95% CI: 0.07-0.97; p=0.049). Conclusion Lower SUV max is associated with better response to SBRT in patients whose disease progressed mainly in adrenal glands.

PO-1475 Definitions and treatment of oligometastatic esophagogastric cancer according to tumor boards

Withdrawn

PO-1476 Early antiarrhythmic efficacy of noninvasive cardiac radioablation for ventricular tachycardia

W.I. Chang 1 , H. Jo 2 , M. Cha 2 , J.H. Chang 1

1 Seoul National University Hospital, Radiation Oncology, Seoul, Korea Republic of; 2 Asan Medical Center, Internal Medicine, Seoul, Korea Republic of Purpose or Objective Noninvasive cardiac radioablation has been reported to be effective and relatively safe for ventricular tachycardia (VT) in preclinical and clinical studies. However, previous studies implementing cardiac radioablation set a 6-12 week “blanking period” and focused on long-term effects rather than reporting the early changes. In this prospective trial, we focused on the early antiarrhythmic effects within one month after cardiac radioablation. In particular, we aimed to determine the differences in response according to the cause of VT. Materials and Methods From September 2019 to December 2020, 6 patients (3 ischemic VTs and 3 non-ischemic VTs) were included in this trial and treated with cardiac radioablation with a single fraction of 25 Gy for intractable VT or premature ventricular contraction- induced cardiomyopathy. Imaging studies, 12-lead ECG, and electrophysiological mapping were used to localize the treatment target. The internal target volume was delineated considering the respiratory motion. To measure the early response after cardiac radioablation, 24-hour Holter monitoring was performed from 24 hours before the treatment to 48