ESTRO 2022 - Abstract Book

S1139

Abstract book

ESTRO 2022

A logistic regression model was calculated considering the two most significant features at the univariate analysis showing the lowest PCC value. The predictive performance of the model created was quantified out using the area under the receiver operating characteristic curve (AUC) as target metric. Results Based on this method, 46 different variables showed significance (p<0.05) at the univariate analysis. The radiomic model showing the highest predictive value combined the features calculated starting from the grey level co-occurrence based features, after the application of the Laplacian of Gaussian filter at two different kernel size (0.7 and 1). Such model exhibited an AUC of 0.73 (95% Confidence interval of 0.61-0.84) in the training set and 0.91 (0.72-1) in the validation set (Fig.1), suggesting its potential clinical use. Conclusion The proposed radiomic model has the ability to predict 2yOS in LACC patients before undergoing NACRT. To confirm the reliability of such results and translate the use of such model in clinical practice, larger studies with a consistent external validation are mandatory.

PO-1344 Comparing Mri And 18fdg-Pet/Ct As Response Evaluation Tools In Locally Advanced Cervical Cancer

M.I. Garrido Botella 1 , M. Rodriguez Roldan 1 , M. Teja Ubach 1 , M. Gonzalez Cantero 1 , I. Rodriguez Rodriguez 1 , E. Gonzalez Del Portillo 1 , B. Belinchon Olmeda 1 , R. Morera 1

1 HOSPITAL UNIVERSITARIO LA PAZ, RADIATION ONCOLOGY, MADRID, Spain

Purpose or Objective Standard treatment in locally advanced cervical cancer (LACC; FIGO stage ≥ IB2) is definitive concurrent chemoradiotherapy (cCRT), with external beam radiotherapy and weekly cisplatin, followed by brachytherapy (BT). In the early assessment of tumoral response, the regression of the tumor could be a survival prognostic factor. By this study we want to compare concordance of magnetic resonance image (MRI) and 18F-fluorodeoxyglucose positron emission tomography – computed tomography (18FDG-PET/CT) as early response evaluation tools, and to describe survival rates in the first 24 months of follow up according to early response. Materials and Methods A retrospective observational study was performed, including patients (n=94) with LACC, treated with cCRT (treatment volume defined according to RTOG guidelines, with 3D conformed radiotherapy or volumetric modulated arc therapy with 6-MV photons, to a total dose of 45-50.4Gy, 1.8Gy per fraction 5 days a week, with dose escalation if positive pelvic nodes or extracapsular extension on paraaortic lymphadenectomy were objectified, and 2-7 cycles weekly cisplatin) followed by high dose rate BT (total dose of 26Gy, 6.5Gy per fraction, twice a week, with Iridium-192, using Ring or Fletcher applicator) between 2010-2018 in our institution. Response to treatment was objectified 18FDG-PET/CT (n=77) performed 3 months after treatment and MRI (n=69) performed 3-6 months after treatment. Results were classified as complete (CR), partial response (PR), stable disease (SD), or disease progression (DP). We described survival rates in patients with CR, PR or SD compared to survival rates in patients with disease progression. Results Same result was obtained in early response assessment by MRI and 18FDG-PET/CT in 69.57% of patients (CI 57.92-79.15). OS after 24 months of follow up in patients with response to treatment or SD objectified in early MNR was 91.8% and 12.5% in patients with DP (p<0.001). Response to treatment or stable disease in MRI affects overall survival, reducing decease risk 96.9% (p<0.001). OS after 24 months of follow up in patients with response to treatment or SD objectified in early 18FDG-PET/CT was 92.6% and in patients with disease progression was 11.1% (p<0.001). Response to treatment or SD in 18FDG-PET/CT affects OS, reducing decease risk 98.6% (p<0.001). Better survival rates were objectified according to better response in both imaging test.