S2432
Physics - Radiomics, functional and biological imaging, and outcome prediction
ESTRO 2026
References: 1.Koh E-S,....Scott, A.M, et al. F-fluoroethyl-L-tyrosine (FET) in glioblastoma (FIG) TROG 18.06 study: protocol for a prospective, multicentre PET/CT trial. BMJ Open. 2023;13:e071327. 2.Barry N, Francis R et al. Delineation and agreement of FET PET biological volumes in glioblastoma: results of the nuclear medicine credentialing program from the prospective, multi-centre trial evaluating FET PET In Glioblastoma (FIG) study—TROG 18.06. Eur J Nucl Med Mol Imaging 2023;50:3970–3981. 3. Barry N, Koh E-S, Ebert, M et al. [18] F-fluoroethyl-l-tyrosine positron emission tomography for radiotherapy target delineation: Results from a Radiation Oncology credentialing program. Physics and Imaging in Radiation Oncology 2024;30:100568. Keywords: Glioblastoma, FET-PET, radiotherapy Digital Poster 1838 Studying brain network hubs using T1-weighted MRI through complex network analysis Gang Yin 1,2 , Lucia Clara Orlandini 1 , Bin Tang 1 , Guoqiang Zhao 1 , Xianliang Wang 1 , Giuseppe Maria Della Pepa 3 , Silvia Chiesa 4 , Vincenzo Valentini 5 , Giuseppe Minniti 5 1 Radiation Oncology, Sichuan Cancer Hospital and Research Institute University of Electronic Science and Technology of China, Chengdu, China. 2 Radiation Oncology, Panzhihua Central Hospital, Panzhihua, China. 3 Neurosurgery, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy. 4 Diagnostic Imaging, Radiation Oncology and Hematology, Fondazione Policlinico Universitario A. Gemelli, IRCCS, Rome, Italy. 5 Radiotherapy and Medical Oncology and Radiology, Isola Tiberina – Gemelli Isola Hospital, Rome, Italy Purpose/Objective: Preserving brain function is a key objective in precision radiotherapy [1]. Diffusion tensor imaging (DTI) may identify functionally relevant brain hubs [2] but is not routinely available in clinical workflows. This study aimed to evaluate whether T1w-MRI can also provide reliable information for identifying stable brain regions through complex network analysis. Material/Methods: A public neuroimaging dataset including raw diffusion- weighted MRI (DW-MRI) and T1w-MRI data from 88 healthy subjects was analyzed. For each subject, DTI were reconstructed from DW-MRI data using standard preprocessing and tensor-fitting procedures. Structural connectivity analyses were independently performed on DTI and T1w-MRI data. The cerebral cortex was parcellated into 90 regions of interest (ROIs) according to the Automated Anatomical
Purpose/Objective: The prospective multi-site phase 2 trial evaluating O- (2-[18F]-fluoroethyl)-L-tyrosine Positron Emission Tomography (FET-PET) in Glioblastoma (FIG), is currently recruiting. Here we aim to describe the outcomes of full central Nuclear Medicine physician (NMP) and Radiation Oncology (RO) review of prospective FET-PET1 delineation of the biological target volume (BTV) for radiotherapy (RT) planning. Material/Methods: Adult Glioblastoma participants across 11 credentialled Australian sites undergo up to 3 FET-PET studies post-surgery/pre-chemo-RT [CRT] (FET-PET1), one month post CRT (FET-PET2) and at suspected pseudoprogression timepoint (FET-PET3). Group 1 participants enter at timepoint 1 (FET-PET1 with MRI1), with Group 2 at timepoint 2. Adjuvant RT target volumes are derived per standard contrast MRI. These are compared to hybrid post-hoc RT volumes incorporating the FET-PET1 NMP-derived BTV. All cases with evaluable FET-PET1 data underwent site then central NMP review of the derived Static “biological” GTV. Once passed, the site RO used the BTV to derive the hybrid target volumes whilst being blinded to the initial clinically treated volumes, which were subject to central RO review. Reasons for case resubmission were documented. Results: Recruitment commenced in January 2021, with 276 participants overall enrolled to date, n=143 with evaluable FET-PET1 data. All n=143 Gp1 with evaluable FET-PET1 data have undergone site then central NMP review. Overall, the initial pass rate was 86%. Compared to 25/72 (35%) in the credentialling phase, reasons for prospective phase case resubmission in 20/143 (14%) included significant BTV under or overcontouring (12/20), static FET interpretation issues (3/20), incorrect background ROI placement or change (2/20) and incorrect imaging selection in MiM workflow (3/20). To date, central RO review of 37/143 hybrid BTV-derived RT volumes has demonstrated an initial pass rate of 68%, with 6/37 (16%) showing clinically significant BTV-undercoverage and a further 6/37 (16%) assigned a conditional pass for reasons including incomplete or inaccurate MRI–PET co- registration, or deviation from protocol-defined OAR or PTV dose constraints. Conclusion: The importance of full central NMP and RO review of all trial prospective cases is substantiated to accurately assess the impact of FET-PET on BTV delineation and future dosimetric and planning impacts. The FIG study remains the largest prospective multi-site study of its kind addressing the impact of FET-PET on radiation planning, management of pseudoprogression and prognostication.
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