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Vienna, Austria

ESTRO 2023

Session Item

Sunday
May 14
16:45 - 17:45
Business Suite 1-2
CNS
Anca-L. Grosu, Germany
Poster Discussion
Clinical
FET-PET incorporation for GBM radiotherapy planning: multi-site FIG Study credentialling programme
Eng-Siew Koh, Australia
PD-0648

Abstract

FET-PET incorporation for GBM radiotherapy planning: multi-site FIG Study credentialling programme
Authors:

Eng-Siew Koh1, Nathaniel Barry2, Martin A. Ebert3, Alisha Moore4, Roslyn J. Francis5, Sweet P. Ng6, Michael Back7, Benjamin Chua8, Mark Pinkham9, Andrew Pullar9, Claire Phillips10, Joseph Sia11, Peter Gorayski12, Hien Le13, Suki Gill3, Jeremy Croker14, Nicholas Bucknell3, Catherine Bettington15, Farhan Syed16, Kylie Jung17, Joe Chang1, Andrej Bece18, Catherine Clark18, Mori Wada19, Andrew M. Scott19

1University of New South Wales, Radiation Oncology, Liverpool Hospital, New South Wales, Sydney, Australia; 2The University of Western Australia, School of Physics, Mathematics and Computing, Crawley, Australia; 3Sir Charles Gairdner Hospital, Department of Radiation Oncology, Nedlands, Australia; 4Trans Tasman Radiation Oncology Group, TROG Cancer Research, Newcastle, Australia; 5Sir Charles Gairdner Hospital, Department of Nuclear Medicine, Nedlands, Australia; 6Austin Health, Department of Radiation Oncology, Heidelberg, Australia; 7Royal North Shore Hospital, Department of Radiation Oncology, Sydney, Australia; 8Royal Brisbane Womens Hospital, Department of Radiation Oncology, Brisbane, Australia; 9Princess Alexandra Hospital, Department of Radiation Oncology, Brisbane, Australia; 10Peter MacCallum Cancer Centre, Department of Radiation Oncology, Melbourne, Australia; 11Peter MacCallum Cancer Centre, Department of Radiation Oncology , Melbourne, Australia; 12Royal Adelaide Hospital, Department of Radiation Oncology, Adelaide, Australia; 13Royal Adelaide Hospital, Department of Radiation Oncology , Adelaide, Australia; 14Sir Charles Gairdner Hospital, Department of Radiation Oncology , Nedlands, Australia; 15Royal Brisbane Womens Hospital, Department of Radiation Oncology , Brisbane, Australia; 16The Canberra Hospital, Department of Radiation Oncology, Canberra, Australia; 17The Canberra Hospital, Department of Radiation Oncology , Canberra, Australia; 18St George Hospital, Department of Radiation Oncology , Kogarah, Australia; 19Austin Health, Department of Radiation Oncology , Heidelberg, Australia

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Purpose or Objective

To analyse the Radiation Oncology (RO) credentialling programme data from the prospective Australian multisite trial evaluating O-(2-[18F]-fluoroethyl)-L-tyrosine Positron Emission Tomography (FET-PET) in Glioblastoma (FIG) study. [ACTRN 12619001735145]. Up to 210 GBM participants will undergo FET-PET post-surgery and pre-chemo-RT (FET-PET1), one month post chemo-RT (FET-PET2) and at suspected progression (FET-PET3) to determine FET-PET’s role in potential radiotherapy treatment planning and in identifying pseudoprogression and prognostication. Observer agreement of RO target volume delineation are reported here.

Material and Methods

Radiotherapy target volumes (GTV, CTV, PTV) is per standard of care (MRI-based) with hybrid post-hoc RT volumes derived by incorporating biologic target volumes (BTV). Nineteen ROs across 10 sites completed TV-MR, TV-MR+FET and CNS organs at risk (OAR) delineation for three different FET-PET1 credentialling cases with BTV delineation by a Nuclear Medicine (NM) expert. Descriptive statistics are given as mean and standard deviation (SD). Pairwise Dice similarity coefficient (DSC) and intraclass correlation coefficient (ICC) with 95% CIs assessed volume overlap and inter-observer agreement, respectively. TV-MR and TV-MR+FET differences were assessed using Wilcoxon signed-rank test.

Results

GTV-MR+FET, CTV-MR+FET, and PTV-MR+FET were significantly larger (p<0.001) than GTV-MR, CTV-MR, PTV-MR (Table 1). Volume agreement between n=19 ROs was moderate to excellent for GTV-MR (ICC = 0.90; 95% CIs, 0.69-1.00) and good to excellent for GTV-MR+FET (ICC = 0.97; 95% CIs, 0.87-1.00). Observer pairwise DSC calculated for each set of target volumes was >0.80 for each credentialling case. OAR mean DSC was highest for brainstem (0.86 ± 0.06) and eyes (left, 0.91 ± 0.03; right, 0.92 ± 0.02) but lowest for optic chiasm (0.46 ± 0.24).

Table 1. Summary of RO target volumes comparing MRI-derived versus MR-FET (mean and standard deviation) for three credentialling cases from the FIG trial demonstrating the hybrid volumes were larger than MRI-only volumes (p<0.001).


Conclusion

Multi-observer hybrid RT volumes were systematically larger than MR-only derived volumes. The incorporation of the BTV increased GTV agreement. Optic chiasm delineation requires greater consistency. This represents one of the largest credentialling multi-site programmes for RO FET-PET volume analysis in GBM RT contouring. This has resulted in increased national expertise in FET-PET interpretation and incorporation into RT planning in preparation for the prospective FIG trial recruitment phase.