ESTRO 2020 Abstract book

S589 ESTRO 2020

We retrospectively analyzed data of 277 patients with 307 lesions treated from April 2010 to December 2015 with Cyberknife SBRT for stage I-II primary lung tumors. We treated even elderly patients, lesions with central location or in close vicinity of the thoracic wall or with a larger size. Dose and fractions numbers were planned according to tumor location and risk-adapted. Local control was defined as the absence of progression. Toxicities were graded according to the CTCAE v4.0. Lung function evaluation pre and post- treatment was performed in the majority of our patients, namely Forced Expiratory Volume in one second (FEV), Diffusion capacity for Carbon Monoxide (DLCO) and Diffusion capacity divided by alveolar volume (DLCO/Va). Results Mean ± SD age of the patients was 72 ± 9 years-old, 60% were men and 90.5% were smokers or ex-smokers. Histologic confirmation was obtained in 76.9% (39.4% adenocarcinoma, 30.9% SCC, 1% SCLC and 5.5% NOS NSCLC) otherwise malignant nature of the nodule was based on either metabolic activity or increase in size. According to 7 th TNM classification, 59.6% were T1a, 24.2% T1b and 16.1% were T2. Mean greatest diameter of the lesion was 2.1 ± 1.1 cm. Location was central in 14% of the cases. Mean BED dose was 152 ± 34.2 Gy (65.6-180 Gy). Real time tracking was performed with either direct fluoroscopy (14.8%) or fiducials (24.9%) otherwise tracking was performed on the vertebra and an ITV concept was used (60.3%). Patients had altered pre-treatment lung functions with a mean FEV of 1.5 ± 0.6 L and 60 ± 20.6 %. DLCO was 39.5 ± 23.7% and DLCO/Va 69.7 ± 24.2%. Median follow-up time was 31.3 months, 80.5% of lesions were either stable or regressed. Local Disease free survival (estimated with Kaplan-Meier method) was at 12 months: 91.2%, at 24 months: 83.2%, at 36 months: 76.9% and at 60 months: 71%. As for OS, they were at 1, 2, 3 and 5 years: 88, 73, 57 and 43.4% respectively. Median OS was 48.8 months. Two patients experienced grade 4 dyspnea but no grade 5 toxicity was reported. No significant decrease in FEV between pre and post- treatment measures was found. In univariate analysis: increasing size (p: 0.0015, HR: 1.036), lower dose (p: 0.0053, HR: 0.946), central position (p: 0.018, HR: 2.06) were associated with a higher risk of local failure. Multivariate analysis confirmed that lesion size (p: 0.0017, HR: 1.04) was associated with higher local failure rates. Conclusion Our data for local control rates are consistent with literature on this large, unselected population. Toxicities are limited and we did not find a significant decrease in respiratory capacity. PO-1020 Does MR imaging give us advantage in contouring thoracic structures for Cardiac SABR? L. Fuertes 1 , M. Dubec 2 , M. Anjanappa 3 , J. Rodgers 3 , R. Hales 3 , A. Clough 3 , M.C. Aznar 2 , A. Choudhury 2 1 Hospital Universitario La Paz, Radiation Oncology, Madrid, Spain ; 2 University of Manchester, Radiotherapy Related Research, Manchester, United Kingdom ; 3 The Christie NHS Foundation Trust, Clinical Oncology, Manchester, United Kingdom Purpose or Objective Cardiac magnetic resonance is the gold-standard imaging technology for identifying scars, the most common cause of ventricular tachycardia (VT) in patients with previous history of myocardial infarction. Recent studies have shown promising results for cardiac SABR ablation of refractory VT. As MR-guided RT (e.g. as delivered on an MR-linac) develops, daily full online replanning guided by MR is becoming a reality. Here, we analyze differences between CT and MR contouring of thoracic structures routinely contoured for cardiac SABR.

Health Sciences- Doctoral School of Health Sciences, Pécs, Hungary Purpose or Objective Lung SABRT (stereotactic ablative body radiotherapy) can be the first choice in the treatment of early stage, node negative non-small cell lung cancer (NSCLC), with the same excellent long-term local control and similar overall survival rates as surgery. Local therapy, like operation or radiotherapy has to be chosen in oligometastatic patients as well, when oligoprogression or de novo oligorecurrence is detected. The number of lung nodules can be 1-3, and the local therapy type is independent of the primary tumour histology. Material and Methods From February 2018 twenty oligometastatic patients were treated with lung SABRT at the Clinic of Oncoradiology, Debrecen. The dose of SABRT could be different, 4x12 Gy or 8x7,5 Gy depending on the localization of the metastatic lesion (central or peripheral). We used dose reduction in few cases, mostly because of the proximity of the chest wall. Ultracentrally localized lesions were excluded. Each treatment plan was based on 4D CT with PET-CT fusion, we determined the internal target volume (ITV) by contouring the gross tumor (GTV) volumes in 3-4 respiratory phases. SABRT treatments started with a day 0. Before treating each fraction a 4D cone-beam CT (CBCT) and a 3D CBCT was made for verification. We analysed the performance state (PS), age, sex of the patients, the time between the development of the primary tumor and the metastatic disease, the localization, number, size of the lesions, the biological effective dose (BED) of the SABRT, the early and late side effects, the local control (morphologic and metabolic changes) and the estimated overall survival. In every 3 months a chest CT, and after 3- 12 months a PET-CT was made for follow up. Results The ECOG PS of the patients was 0-2, age was between 32- 82 years. The most common primary tumor type was NSCLC, colorectal cancer and melanoma malignum. The maximum size of the treated lesions was 4 cm. We irradiated one or two lesions simultaneously. Grade 2-3 acute side effects did not develop. The most common late side effect was asymptomatic lung fibrosis in the treatment area. Other serious adverse effects did not occur. After the first year of follow up stable disease or locally partial response was observed based on the metabolic and morphologic information. New lung or other site metastases were evolved in 4 cases so far. Conclusion Lung SABRT for oligometastatic patients is a well tolerable, effective treatment, which is easily and safely feasible after precise planning. The factors, which most affects local control, are BED and fractional dose based on the literature. Yet, because of the short follow up time, we can only estimate the overall survival, but our local control data corresponds with literature data. PO-1019 Long term outcomes and lung function evolution of primary lung tumors treated with Cyberknife SABR F. Sacino 1 , N. Jansen 1 , C. Mievis 1 , L. Seidel 2 , S. Cucchiaro 1 , P. Coucke 1 1 CHU - Sart Tilman, Radiotherapy department, Liège, Belgium ; 2 CHU - Sart Tilman, Biostatistics- SIME, Liège, Belgium Purpose or Objective To report local control and toxicity including pulmonary function for patients treated with robotic stereotactic body radiotherapy (SBRT) for primary lung tumors. Cox regression models were performed to identify factors influencing local tumor control. Material and Methods