ESTRO 2022 - Abstract Book

S841

Abstract book

ESTRO 2022

Proffered Papers: Dosimetry & treatment planning

OC-0948 Prognostic value of 18F-FDG PET/CT performed before reirradiation of head and neck squamous cell carcinoma recurrence

F. Lucia 1 , A. Vu 2 , V. Bourbonne 1 , C. Clodic 3 , J. Leclerc 3 , O. Pradier 4 , R. Abgral 5 , U. Schick 4

1 University hospital of Brest, Radiation therapy, Brest, France; 2 University hospital of Brest, Radiation Therapy, Brest, France; 3 University hospital of Brest, Head and neck Surgery, Brest, France; 4 University Hospital of Brest, Radiation therapy, Brest, France; 5 University Hospital of Brest, Nuclear medicine, Brest, France Purpose or Objective Up to 50% of patients treated with radiotherapy (RT) with a curative intent for a head and neck squamous cell carcinoma (HNSCC) will present a loco-regional recurrence or a second primary tumor. When salvage surgery is not possible, re- irradiation (reRT) should be discussed. As the benefit-risk balance is uncertain, biomarkers to select patients are needed. The purpose of this study was to establish the prognostic value of 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET/CT) features before reRT of patients with a loco-regional HNSCC recurrence. Materials and Methods Patients who underwent a 18F-FDG PET/CT before reRT for a loco-regional HNSCC recurrence between 2012 and 2020 were retrospectively included. A gross tumor volume (GTV) corresponding to primary disease with nodal disease if present was segmented using a gradient-based method (PET-Edge) embedded in MIM Maestro© v7.0 (MIM©, Cleveland, OH, USA). From each volume, maximum standardized uptake value (SUVmax), peak of SUV (SUVpeak), mean of SUV (SUVmean), metabolic tumor volume (MTV), total lesion glycolysis (TLG), maximum tumor to blood ratio (TBRmax) and maximum tumor to liver ratio (TLRmax) were calculated. Usual clinical features at the time of recurrence were collected and analyzed. A cox regression-based model was developed for the prediction of overall survival (OS) and also evaluated for the prediction of disease local control (LC) and disease-free survival (DFS). Results Thirty patients met inclusion criteria with a median follow up of 6.5 months (range 1-38 months). Median OS, LC and DFS were 6 months (95CI% 3-12 months), 4 months (95CI% 2-6 months) and 3 months (95CI% 2-6 months), respectively. MTV (p=0.007), TLG (p=0.028), tumor recurrence site (p=0.022) and head and neck organ dysfunction (HNOD) (p=0.018) were significantly correlated with OS. MTV (p=0.045) and tumor recurrence site (p=0.016) remained independent significant prognostic factors of OS after multivariate analysis. When these 2 parameters were logistically combined, the model significantly stratified patients at low and high-risk for OS (HR=3.4; 95%CI 1.5-7.7), LC (HR=3.6; 95%CI 1.3-9.8) and DFS (HR=3.2; 95%CI 1.3-7.7). Conclusion MTV volumetric PET parameter and tumor recurrence site may be significant prognostic factors in patients reirradiated for a head and neck relapse. These findings need to be confirmed in prospective and larger populations, but could help clinicians for a better selection of patients eligible for reRT.

OC-0949 Improved sparing of liver and lung tissue: DIBH for right breast irradiation

R. Pace 1 , R.T. Boucas da Silva 1 , L.E.J. Adam 1 , G. Näf 1 , C. Winter 1 , M.M. Aspradakis 2 , S. Hayoz 3 , B.G. Baumert 1

1 Kantonsspital Graubünden, Institute of Radiation Oncology, Chur, Switzerland; 2 Kantonsspital Grabünden, Institute of Radiation Oncology, Chur, Switzerland; 3 Swiss Group for Clinical Cancer Research (SAKK), Statistics, Bern, Switzerland