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
Creators: name: Barry, N
name: Francis, RJ
name: Ebert, MA
name: Koh, ES
name: Rowshanfarzad, P
name: Hassan, GM
name: Kendrick, J
name: Gan, Hui
name: Lee, Sze
name: Lau, E
name: Moffat, BA
name: Fitt, G
name: Moore, A
name: Thomas, P
name: Pattison, DA
name: Akhurst, T
name: Alipour, R
name: Thomas, EL
name: Hsiao, E
name: Schembri, GP
name: Lin, P
name: Ly, T
name: Yap, J
name: Kirkwood, I
name: Vallat, W
name: Khan, S
name: Krishna, D
name: Ngai, S
name: Yu, C
name: Beuzeville, S
name: Yeow, TC
name: Bailey, D
name: Cook, O
name: Whitehead, A
name: Dykyj, R
name: Rossi, A
name: Grose, A
name: Scott, Andrew
Publisher: name: La Trobe
Year: 2023
Subjects: classificationCode: 3202
subject: Clinical sciences

description: Purpose: The O-(2-[18F]-fluoroethyl)-l-tyrosine (FET) PET in Glioblastoma (FIG) trial is an Australian prospective, multi-centre study evaluating FET PET for glioblastoma patient management. FET PET imaging timepoints are pre-chemoradiotherapy (FET1), 1-month post-chemoradiotherapy (FET2), and at suspected progression (FET3). Before participant recruitment, site nuclear medicine physicians (NMPs) underwent credentialing of FET PET delineation and image interpretation. Methods: Sites were required to complete contouring and dynamic analysis by ≥ 2 NMPs on benchmarking cases (n = 6) assessing biological tumour volume (BTV) delineation (3 × FET1) and image interpretation (3 × FET3). Data was reviewed by experts and violations noted. BTV definition includes tumour-to-background ratio (TBR) threshold of 1.6 with crescent-shaped background contour in the contralateral normal brain. Recurrence/pseudoprogression interpretation (FET3) required assessment of maximum TBR (TBRmax), dynamic analysis (time activity curve [TAC] type, time to peak), and qualitative assessment. Intraclass correlation coefficient (ICC) assessed volume agreement, coefficient of variation (CoV) compared maximum/mean TBR (TBRmax/TBRmean) across cases, and pairwise analysis assessed spatial (Dice similarity coefficient [DSC]) and boundary agreement (Hausdorff distance [HD], mean absolute surface distance [MASD]). Results: Data was accrued from 21 NMPs (10 centres, n ≥ 2 each) and 20 underwent review. The initial pass rate was 93/119 (78.2%) and 27/30 requested resubmissions were completed. Violations were found in 25/72 (34.7%; 13/12 minor/major) of FET1 and 22/74 (29.7%; 14/8 minor/major) of FET3 reports. The primary reasons for resubmission were as follows: BTV over-contour (15/30, 50.0%), background placement (8/30, 26.7%), TAC classification (9/30, 30.0%), and image interpretation (7/30, 23.3%). CoV median and range for BTV, TBRmax, and TBRmean were 21.53% (12.00–30.10%), 5.89% (5.01–6.68%), and 5.01% (3.37–6.34%), respectively. BTV agreement was moderate to excellent (ICC = 0.82; 95% CI, 0.63–0.97) with good spatial (DSC = 0.84 ± 0.09) and boundary (HD = 15.78 ± 8.30 mm; MASD = 1.47 ± 1.36 mm) agreement. Conclusion: The FIG study credentialing program has increased expertise across study sites. TBRmax and TBRmean were robust, with considerable variability in BTV delineation and image interpretation observed.