ESTRO 2022 - Abstract Book

S65

Abstract book

ESTRO 2022

Conclusion Slight differences with more skin toxicity but less weight loss was observed with proton therapy in this case control study. Regarding acute toxicity, proton treatment seemed safe.

OC-0090 Temporal lobe necrosis after proton therapy for skull base tumors and NTCP models evaluation

G. Riva 1 , E. Fiorina 2 , I. Cavallo 3 , S. Molinelli 4 , A. Vai 4 , M. Ciocca 4 , A. Iannalfi 3 , E. Orlandi 3

1 Centro Nazionale di Adroterapia Oncologica CNAO, Radiotherapy, PAVIA, Italy; 2 Centro Nazionale di Adroterapia Oncologica CNAO, Clinical Department - Medical Physics Unit, PAVIA, Italy; 3 Centro Nazionale di Adroterapia Oncologica CNAO, Clinical Department, Pavia, Italy; 4 Centro Nazionale di Adroterapia Oncologica CNAO, Clinical Department - Medical Physics Unit, Pavia, Italy Purpose or Objective The aims of this study were: i) to analyze the relationship between radiation induced temporal lobe necrosis (TLN) and dosimetric features in patients with skull base tumors treated with pencil beam scanning proton therapy (PT); ii) to test available normal tissue complication probability (NTCP) models. Materials and Methods Clinical and dosimetric data of 110 adult consecutive skull base chordoma and chondrosarcoma patients treated at CNAO between September 2011 and July 2020 were retrospectively analyzed. A median dose of 70 Gy (RBE) (range 70-74 Gy (RBE)) was planned and delivered in 35-37 daily fractions. Current treatment planning goal for TL was limiting the maximum dose to the hottests 2 cm 3 (D 2cc ) to 71 Gy (RBE). Magnetic Resonance Imaging (MRI) studies showing TLN at the first occurrence were co-registered with the original planning images. TLN was graded using Common Terminology Criteria for Adverse Events (CTCAE) v 5.0. The dosimetric parameters of TLs (Figure 1) were investigated for finding a correlation with the TLN’s occurrence and severity and then included in NTCP univariate models. Their classification and predictive performances were evaluated by means of goodness of fit (R 2 ); Area Under ROC Curve (AUC); accuracy, sensitivity and F- score.