Glioblastoma is the most common adult primary brain malignancy with a poor prognosis [1]. Recent ESTRO-EANO guidelines define gross tumour volume (GTV) as resection cavity after surgery plus any residual enhancing tumour on contrast-enhanced T1-weighted MRI (T1c), with expansion to clinical target volume (CTV) using a margin of 15 mm. Furthermore, changes on T2-weighted and T2 fluid attenuated inversion recovery (FLAIR) that are felt to reflect non-enhancing tumour should be incorporated into the CTV [2]. There has been ongoing research into alternative target volume (TV)...

At least one RO per study site completed three benchmarking cases (Table 1). Firstly, ROs were instructed to delineate standard of care MRI-derived target volumes (TVMR). CTVMR expansion was 15 mm and PTVMR expansion was 3 mm. Afterwards, ROs were then instructed to incorporate FET-PET biological tumour volumes (BTVs) into revised adjuvant radiation target volumes (TVMR+FET). CTVMR+FET expansion was 10-15 mm and PTVMR+FET expansion was 3 mm. Organs at risk (OARs) were also delineated (All cases: brainstem, optic chiasm; FET-PET1 CASE1 only: optic nerves, retinas,...

Data was accrued from 19 RO observers across 10 trial sites. Case reviews were conducted on 54 initial submissions, with eight additional requested resubmissions (n=6, missing contour(s); n=2, contour data not registered to planning CT) and four conditional passes (n=3, image registration misalignment; n=1, missing contour(s)). Initial pass rate was 42/54 (77.8%) (Figure 1). The ten radiation therapy plans were reviewed which utilised four various treatment planning systems (Monaco, Pinnacle, Raystation, Eclipse). All plans were within specific FIG RT quality assurance manual dose constraints, with...

The RO credentialing program for the FIG Study has resulted in all sites successfully passing all mandatory requirements, in parallel with completion of the NM credentialling aspects [9]. Specifically, the credentialling program has provided ROs with an opportunity to increase their expertise in incorporating FET-PET BTVs into radiation target volume definitions. RO variability was similar between MR and MRI+FET derived volumes. During the prospective recruitment study phase of the FIG Study, BTVs will be created by the credentialed site NMP, which will then undergo central...

Stupp R, Hegi ME, Mason WP, van den Bent MJ, Taphoorn MJB, Janzer RC, et al. Effects of radiotherapy with concomitant and adjuvant temozolomide versus radiotherapy alone on survival in glioblastoma in a randomised phase III study: 5-year analysis of the EORTC-NCIC trial. The Lancet Oncology. 2009;10:459-66. doi:10.1016/s1470-2045(09)70025-7. Niyazi M, Andratschke N, Bendszus M, Chalmers AJ, Erridge SC, Galldiks N, et al. ESTRO-EANO guideline on target delineation and radiotherapy details for glioblastoma. Radiotherapy and Oncology. 2023;184:109663. Galldiks N, Niyazi M, Grosu AL, Kocher M, Langen...