ESTRO 2022 - Abstract Book

S1086

Abstract book

ESTRO 2022

E. Ferrara 1 , E. Puta 2 , R. Guaschino 1 , L. Turri 1 , P. Franco 1,3 , S. Gentilli 4 , G.M. Sacchetti 2 , M. Brambilla 5 , M. Krengli 1,3

1 University Hospital Maggiore della Carità, Novara, Italy, Radiation Oncology, NOVARA, Italy; 2 University Hospital Maggiore della Carità, Novara, Italy, Nuclear Medicine, NOVARA, Italy; 3 University of Piemonte Orientale, Italy, Dept. Of Translational Medicine, NOVARA, Italy; 4 University Hospital Maggiore della Carità, Novara, Italy, General Surgery, NOVARA, Italy; 5 University Hospital Maggiore della Carità, Novara, Italy, Medical Physics, NOVARA, Italy Purpose or Objective The aim of the present study was to evaluate the role of semiquantitatve PET parameters as possible prognostic and predictive factors in a series of oesophageal carcinomas treated with combined modality treatment. Materials and Methods A series of 43 patients affected with oesophageal carcinoma and treated with chemo-radiotherapy (CRT) followed by surgery in 20 cases, underwent pre-treatment 18F-FDG PET/CT. Semiquantitaive PET parameters were evaluated including Standardized Uptake Value (SUVmax e SUVmean), Metabolic Tumour Volume (MTV) and Total Lesion Glycolysis (TLG) with isocontour of 41% and 50%. Further variables analysed were gender, primary tumour site, histological type, use of surgery, achievement of a radical resection and chemotherapy regimen. The correlation of all variables with treatment response, loco-regional control (LR control) Overall (OS) and Disease Free (DFS) Survival was evaluated with log-rank, Student’s t- and Chi-squared tests. Results As possible predictive factors, pre-treatment PET parameters did not show significant differences between responders (partial or complete response) and non-responders (stable or progressive disease) (p-values ≥ 0.10). In terms of prognostic factors, MTV correlated with better OS: patients with MTV41 <11.32 cm 3 and MTV50 <8.07cm 3 (both p-value=0.04) showed better 3-year survival rates (33% vs. 20%). Further factors predicting for better prognosis were the use of surgery and radical resection (R0) (both p-value <0.01). Of note, there was no correlation between MTV and surgery (p-value =0.1). Conclusion The present study shows that, among pre-treatment PET parameters, MTV values resulted to be significant prognostic factors for OS, together with the use of surgery and R0 resection. 1 SS. Annunziata Hospital, "G. D'Annunzio" University, Department of Radiation Oncology, Chieti, Italy; 2 G. D’Annunzio University, Department of Neuroscience, Imaging and Clinical Sciences, Chieti, Italy Purpose or Objective Radiation therapy is an effective therapeutic strategy for pancreatic cancer (PC), especially in terms of local-regional control, and stereotactic body radiation therapy (SBRT) is gaining more importance as treatment option, thanks to high spatial precision. This study was conducted to analyse the results of a dose-painting SBRT approach with higher biologically effective doses released on tumour-vessel interface (TVI) to increase surgical resectability and reduced doses on simultaneous integrated protection (SIP) to protect duodenum for unresectable PC. Materials and Methods Frameless set-up was used for CT simulation. Gross Tumor Volume (GTV) and involved major blood vessels were contoured by a dynamic co-registration of CT simulation with contrast medium diagnostic CT scan. CTV was delineated including tumour-vessel interface (CTV= GTV+TVI) obtained by expanding of 5mm blood vessels volume. A Planning target volume (PTV) was obtained adding 5mm to Internal Target Volume (ITV), generated by 4DCBCT (Symmetry TM ). Within the PTV, two volumes were delineated: a PTV boost created to cover the tumor-vessel interface inside the GTV with higher dose and a PTV SIP (Simultaneous integrated protection) defined as the intersection between the PTV and the Planning Organ at Risk (PRV) for the duodenum (duodenum + 3mm), inside which the prescription dose was reduced according to OAR dose constraints (UK Consensus SBRT 2018), and. A differential dose distribution by a Simultaneous Integrated Boost (SIB) technique was planned. Results Four pilot cases have been analyzed. Dose constraint for duodenum was set as maximum dose (0.5cc) <33Gy (5 fractions). Dose prescription on all cases was 35Gy (5 consecutive daily fraction, 60Gy BED10), with minimal dose to PTVs of 25Gy, and 40Gy on PTV boost (72Gy BED10). Case1: PTV volume =52cc, PTV SIP volume =12cc, PTV boost volume =8cc. Case2: PTV volume =126cc, PTV SIP volume =15cc, PTV boost volume =57cc. Case3: PTV volume =107cc, PTV SIP volume =10cc, PTV volume boost=44cc; Case4: PTV volume =109cc, PTV SIP volume =22cc, PTV boost volume =21cc. In the four cases, the mean dose on PTV were 35.5, 36.7, 37.1, 35Gy, the mean dose on PTV SIP were 32, 31, 33, 30Gy, the mean dose on PTVs boost were 40, 41, 39, 41Gy and the maximum dose on PTVs boost were 41.7, 42.3, 41, 42Gy, respectively. Volumes and dose distribution of Case1 is showed in Figure 1. PO-1288 Dose-Painting Sbrt On Tumor-Vessel And Duodenal Interface For Pancreatic Cancer: Dosimetric Analysis L. Caravatta 1 , M. Lucarelli 1 , A. Augurio 1 , C. Rosa 1,2 , M. Trignani 1 , D. Genovesi 1,2