ESTRO 2020 Abstract book

S582 ESTRO 2020

tomography (PET) CT imaging study for each patient was used for segmentation. All FDG-avid intrathoracic tumors were delineated on the CT scan per RTOG contouring guidelines. Normal lung was contoured through thresholding in a commercial treatment planning system. The tumors were subtracted from the normal lung and radiomics were extracted with an in-house developed software for the resultant region of interest (ROI). 108 first-, second-, and third-order texture features within the ROI for each patient were analyzed for association with the primary endpoint. A univariate logistic regression model was used to estimate odds ratio (OR), the p-value, and receiver operating characteristic curves (ROC) for each imaging feature. Results Six out of 108 texture features showed significant association with CIP (p-values ranging from 0.02 to 0.03) and all exhibited large effect (OR < 0.3 or > 3.5). Despite the low number of events (only 9 out of 49) the ROC curves yielded values ranging from 0.789 to 0.794.

of LC showed HR tumor size 1.04 (95% CI 1.02-1.06, p = 0.001) and HR FEV 1 of 0.97 (95% CI 0.95-1.00, p = 0.031). LC was 88% at 2 years and 81% at 3 years. Twenty-seven patients (12%) developed a local recurrence. Disease progression was reported in 75 patients (34%). DFS was 66% at 2 years and 56% at 3 years. UVA results for DFS are listed in Table 1. MVA of DFS showed HRs for tumor size 1.03 ( p < 0.001), FEV 1 0.98 ( p = 0.004) and localization of the tumor 1.87 ( p = 0.017).

Conclusion Underdosage of the PTV is not affecting the local recurrence probability, however a prescribed dose of <100 Gy BED 10 doubles the chance on a local recurrence. Larger tumor size and lower FEV 1 were both independently associated with local recurrence and disease recurrence, aditionally a tumor located in the lower lobe was associated with disease recurrence. PO-1006 Immunotherapy related pneumonitis correlates with radiomics in NSCLC patients treated with Nivolumab I. Mihaylov 1 , G. Lopes 2 , D. Saravia 2 , D. Kwon 3 , R. Yechieli 1 , A. Dal Pra 1 , L. Freedman 1 , T. Diwanji 1 , B. Spieler 1 1 University of Miami, Radiation Oncology, Miami, USA ; 2 University of Miami, Medical Oncology, Miami, USA ; 3 University of Miami, Biostatistics and Bioinformatics, Miami, USA Purpose or Objective Immune checkpoint inhibitors (ICI) offer a new paradigm in cancer treatment. For patients with advanced non- small cell lung cancer (NSCLC), immunotherapy (IT) has led to significant improvements in survival and quality of life. IT also has been associated with debilitating and sometimes life-threatening immune-related adverse events (irAEs) such as pneumonitis, colitis, hypophysitis, inflammatory arthritis and thyroiditis. Methods that predict normal tissue toxicity to IT could inform clinical decision-making and further personalize patient care. Radiomics, the study of diagnostic imaging for patterns of intensity indiscernible to the naked eye, has been used to construct predictive models for tumors. We hypothesized that for patients with advanced NSCLC treated with Nivolumab after frontline chemotherapy, radiomics of pre- IT computed tomography (CT) lung imaging correlate with the incidence of checkpoint inhibitor pneumonitis (CIP). Material and Methods Forty-nine patients were selected for preliminary analyses from an IRB-approved database of 159 patients with advanced NSCLC treated with Nivolumab after frontline chemotherapy. Nine of those patients had confirmed CIP, the primary endpoint. The last pre-IT positron emission

Conclusion This preliminary study suggests that texture features on pre-immunotherapy CT imaging can be linked to CIP for patients with advanced NSCLC treated with Nivolumab. Future directions of this research include expansion of this study across the full database, correlation of the radiomics features with blood biomarkers, and the inclusion of tumor burden as an additional covariate in the analyses. PO-1007 Predictors of radiation pneumonitis in early stage lung cancer treated with SABR. A. Saha 1 , N. Hatton 1 , M. Beasley 1 , K. Franks 1 , P. Jain 1 , M. Teo 1 , K. Clarke 1 , P. Dickinson 1 , P. Murray 1 , J. Lilley 2 1 St. James Institute of Oncology- Leeds Teaching Hospitals- NHS trust, Clinical Oncology, Leeds, United Kingdom ; 2 St. James Institute of Oncology- Leeds Teaching Hospitals- NHS trust, Medical Physics, Leeds, United Kingdom Purpose or Objective Predictors of radiation pneumonitis (RP) in Stereotactic Ablative Radiotherapy (SABR), the standard treatment for medically inoperable peripheral early stage lung cancer, are poorly defined. In this study, we aimed to identify clinical and dosimetric parameters which can predict symptomatic RP in early stage lung cancer patients treated with SABR. Material and Methods 1266 patients treated with SABR in our institute (May 2009 -August 2018) were included. Electronic medical records were reviewed for baseline characteristics, treatment details and toxicity. Dosimetric data was extracted from XIO and Monaco software. Patients were treated according to the UK SABR consortium guidelines. RP was graded retrospectively using CTCAE version 4, based on available clinical and imaging information. Univariate and multivariate binary logistic regression were performed to determine predictive factors for grade ≥2 RP, using IBM SPSS statistics version 21 software. Goodness of fit was assessed using the Hosmer and Lemeshow test. Optimal