Abstract book - ESTRO meets Asia

S34 ESTRO meets Asia 2018

to OS (p=0.06). PLR level significantly affected both PFS (p<0.01) and OS (p=0.02). On multivariate analysis pre- treatment SII level was significantly correlated to PFS (p=0.0079), but not to OS (p=0.15). We developed a logistic nomogram using SII, nodal status and pre- treatment haemoglobin levels as variables to predict the chance to respond/not respond to treatment. The nomogram was then externally validated on a cohort of 147 anal cancer patients treated in Italy and France. Results showed a good predictive ability with a C- index of 0.74. An online available calculator (ARC: Anal cancerResponse Classifier) was also created.

accuracy. Radiomics features were extracted using a dedicated software and correlated with the corresponding delivered dose. The variations of each feature throughout the treatment were then quantified and the ratio between the values calculated at different dose levels and the one extracted at t0 was calculated too. The Wilcoxon Mann Whitney test was performed to identify the features whose variation can be predictive of cCR. Complete clinical response was assessed with a diagnostic 1.5 T MR acquired 6 weeks after CRT and digital rectal examination (DRE), according to the usual workflow.

Conclusion The low cost and easy profile in terms of determination and reproducibility make SII a promising tool for prognostic assessment in anal cancer patients treated with concurrent CT-RT. OC-086 Radiomics for response prediction in hybrid MR guided RT: generating hypothesis in rectal cancer L. Boldrini 1 , D. Cusumano 1 , C. Masciocchi 1 , F. Cellini 2 , G. Chiloiro 1 , C. Casà 1 , N. Dinapoli 2 , L. Azario 3 , M.A. Gambacorta 1 , M. De Spirito 3 , V. Valentini 1 1 Istituto di Radiologia- Fondazione Policlinico A. Gemelli Radioterapia Oncologica ed Ematologia, Roma, Italy 2 Fondazione Policlinico Universitario A. Gemelli IRCCS, Dipartimento di Diagnostica per Immagini- Radioterapia Oncologica ed Ematologia, Roma, Italy 3 Istituto di Fisica- Fondazione Policlinico A. Gemelli IRCC S - Università Cattolica del Sacro Cuore, Dipartimento di Diagnostica per Immagini- Radioterapia Oncologica ed Ematologia, Roma, Italy Purpose or Objective Aim of this study was to evaluate the variation of radiomics features, defined as 'delta radiomics”, in patients (pts) affected by locally advanced rectal cancer (LARC) undergoing hybrid MR guided radiotherapy (MRgRT) and correlate it with complete clinical response (cCR) prediction outcome. Material and Methods T2*/T1 MR images acquired with a hybrid 0.35 T MRgRT unit from pts undergoing neoadjuvant chemoradiotherapy (CRT) were considered for this analysis. Prescribed dose was 55 Gy to primary tumor and corresponding mesorectum (PTV1) and 45 Gy to pelvic nodes and mesorectum in toto (PTV2) delivered through a simultaneous integrated boost 2 approach (SIB2). A specific imaging acquisition protocol of 6 MR high resolution 175 seconds scans was performed in all the patients: the first MR was acquired at first simulation (t0) and the remaining ones at fractions 5,10,15,20 and 25 (t5, t10, t15, t20, t25). A true fast imaging with steady state precession (TRUFI) sequence was used for all image acquisitions with a resolution of 1.5x1.5x1.5 mm 3 and acquisition time of 175 sec. The gross tumor volume (GTV) contours were performed by two radiation oncologists to ensure their IRCCS - Università Cattolica del Sacro Cuore, Dipartimento di Diagnostica per Immagini-

Results 16 pts (13 male and 3 female) were enrolled in this hypothesis generating study. 5 pts (31%) showed cCR at restaging MRI and DRE. 53 radiomics features (morphological, statistical, textural and fractal) were firstly analyzed, while a total of 260 ratios of features was then calculated, defining the 'delta radiomics approach” throughout the CRT treatment. 57 of these features resulted to be significant in discriminating cCR pts from not responding ones and 4 of them showed significance for all considered ratios, demonstrating a continuous predictive power for the considered outcome. The most significant feature appeared to be the ratio between the 'L least”, that is the axis along which the object is least extended, calculated during the second week (t 10, dose level:22 Gy) of treatment and the corresponding value obtained during simulation (t0, dose level 0 Gy) (p < 0,0005). Conclusion The observed results suggest that radiomics analysis is feasible on 0.35 T images and that the described delta radiomics approach can successfully predict cCR in MRgRT, Clinical Outcomes in Esophageal Cancer X. Li 1,2 , P. Yang 3 , Y. Kuang 4 , T. Niu 5 , S. Wu 6 1 Sir Run Run Shaw Hospital- School of Medicine- Zhejiang University-, Radiation Oncology, Hangzhou, China 2 The First People’s Hospital of Hangzhou, Radoitherapy, Hangzhou, China 3 Sir Run Run Shaw Hospital School of Medicine Zhejiang University, Transfer Research Institute on Medical Physics, Hangzhou, China 4 University of Nevada, Department of Medical Physics, Las Vegas, USA 5 Sir Run Run Shaw Hospital- Zhejiang University, School of Medicine, Hangzhou, China 6 Hangzhou Tumor Hospital, Radiation Oncology, Hangzhou, China allowing innovative treatment personalization in LARC pts. OC-087 A Radiogenomics Framework to Improve Prediction of