ESTRO 2020 Abstract book

S499 ESTRO 2020

Massaccesi 1 , V. Valentini 1 1 Fondazione Policlinico Universitario A. Gemelli IRCCS, UOC di Radioterapia Oncologica- Dipartimento Diagnostica per Immagini- Radioterapia Oncologica ed Ematologia, Rome, Italy ; 2 Università Cattolica del Sacro Cuore, Radiotherapy Oncology, Rome, Italy ; 3 Azienda- Ospedaliero-Universitaria Careggi- University of Florence, radiotherapy oncology, florence, Italy ; 4 Policlinico San Martino, radiotherapy oncology, genova, Italy ; 5 S. Croce and Carle Teaching Hospital, radiotherapy oncology, cuneo, Italy ; 6 Azienda Ospedaliero Universitaria- Policlinico di Modena, radiotherapy oncology, modena, Italy ; 7 University of Turin, radiotherapy oncology, torino, Italy ; 8 Dip. Scienze della salute DISSAL Università di Genova, radiotherapy oncology, genova, Italy ; 9 S. Croce and Carle Teaching Hospital, oncology, cuneo, Italy ; 10 AOU Citta' della Salute e della Scienza, oncology-radiotherapy oncology, turin, Italy ; 11 Fondazione Policlinico Universitario A. Gemelli IRCCS, radiotherapy oncology, rome, Italy Purpose or Objective In the last decade, remarkable advances in cancer care pose new challenges, leading clinical practice towards personalized medicine to understand the different behaviour of the same tumour in different patients. Aim of this study is developing a predictive model of overall survival (OS) for patients (pts) with oropharynx cancer treated with radiotherapy (RT) and Cetuximab (Cet), coming from PRO.M.E.THE.O.(PRedictiOn Models in Ent cancer for anti-EGFR based THErapy Optimization) italian Pts with oropharynx cancer treated with RT-Cet coming from 6 centres (Cuneo, Firenze, Genova, Modena, Roma, Torino), were considered for this analysis.We considered different variables: age at diagnosis, gender, PS ECOG, TNM stage, total dose at CTV High Risk, fractionation, overall treatment time, RT interruption days.Follow-up times (2, 3, and 5 years) for the OS were used as the model outcome.Pts were randomly divided into two different groups: group A (training set) corresponding to 80% of dataset and group B (validation set) representing the remaining 20%.A binary logistic regression model was trained on group A with stepwise feature selection based on Akaike's information criterion (AIC). The model was then performed on testing set. ROC- AUC (Receiver Operating Characteristics- Area Under the Curve) and confusion matrix statistics at 5 threshold were used as performance criteria. Nomograms were performed at 2, 3 and 5 years. Results Of 218 pts collected, 183 (84%) were selected and analysed. OS predictive models were developed and represented by nomograms at 2,3 and 5 years. Covariates that show negative impact on 2y OS were positive nodal status, PS ECOG  1, Age, dose < 66Gy and interruption days of radiotherapy >3 days. ROC AUC for training set and testing set for OS at 2years was 0.787 (figure 1) and 0.763 (figure2)respectively . multicentric dataset Material and Methods

PO-0841 Treatment failure patterns after radical radiotherapy using modern radiation techniques. C.A.D.N. Laranja 1 , I. Rodrigues 1 , T. Ramos 1 , B. Castro 1 , F. Sousa 1 , D. Moreira 1 , I. Reis 1 , A. Soares 1 1 Instituto Português de Oncologia do Porto, Radioterapia externa, Porto, Portugal Purpose or Objective The recommended treatment in head and neck cancer (HNC), mainly in advanced stages involves an association of radiotherapy (RT) and Chemotherapy. However, locoregional recurrences are seen in 15 to 50 percent of these pts. Recurrent disease is an important cause of morbidity and mortality with impact in long term survival. The aim of this study was to assess patterns of locoregional treatment failure in HNC patients (pts) treated with radical RT using modern radiation techniques (3DCRT, IMRT and VMAT). Focus was given on the relation between treatment volumes, dosimetry and local of recurrence/persistence. We also analyzed the impact of treatment failure, in terms of overall survival(OS) and locoregional control (LRC) Material and Methods Retrospective analysis of 314 pts treated between January 2015 and December 2018. Only pts with squamous cell tumors of Larynx, Oropharynx and Hypopharynx were included. Our analysis considered recurrent disease, pts who had at least one imagiologic control exam after the end of RT with no evidence of disease before the relapse, otherwise was considered persistent disease. Completing the prescribe treatment dose (63Gy for Larinx and 50-70Gy for Oropharynx and Hypopharinx) was an inclusion criteria of our study. Planning target volume (PTV) 70 was defined as the PTV receiving 70Gy, PTV60 the PTV receiving 60Gy and PTV50 the PTV receiving 50Gy. Results From the 314 pts analyzed, we identified 89 loco-regional treatment failures, 45 as recurrent disease and 44 as persistent disease. In pts that undergone induction chemotherapy and had advanced T stages (T3-T4) persistent disease (59%) was more common than recurrence (41%). Most of the relapses occurred in pts treated with VMAT (79 pts), followed by IMRT (8 pts) and 3DCRT (2pts) Median follow-up were 31.6 months [IC 95% 27.6-35-.6]. The median time for recurrence after RT was 6.8 months and 3-year OS were 25.9%. 3-year LRC rates were 72.4% for Oropharynx, 65.9% for Hypopharynx and 76.8% for Larynx. A vast majority of treatment failure occurred within the irradiated field (83 pts - 87.6%). Four pts relapse out of radiation field (2 in mediastinal upper nodes –Level VII, 1 in pretracheal nodes level VI and 1 in skull base) and only 2 marginal failures were observed. Among the in-field failures, 55 occurred exclusively on the PTV70 (66%), 9 (11%) involved PTV 70+PTV60, 7 (8%) were within PTV70+PTV60+PTV50, 8(10%) were observed in PTV70+PTV50 and only 4 (5%) were exclusively in the PTV50. Conclusion Our results showed that majority of treatment failures occurred within the irradiated volumes, in the areas of high doses. These findings corroborate the evidence on the literature, suggesting that this fact could be associated with a inherent radioresistance of the tumour cells. The small number of marginal/out of field treatment failures in our study indicates that VMAT and IMRT could be a effective and feasible technique for treating these pts. PO-0842 PRO.M.E.THE.O.: the development of an italian multicentric OS predictive model in oropharynx cancer F. Miccichè 1 , G. Chiloiro 1 , S. Longo 2 , P. Bonomo 3 , A. Bacigalupo 4 , A. Merlotti 5 , E. D'angelo 6 , P. Franco 7 , L. Belgioia 8 , I. Desideri 3 , N. Denaro 9 , B. Meduri 6 , F. Arcadipane 10 , J. Lenkowicz 1 , A. Pesce 1 , R. Autorino 11 , M.