RESUMEN
PURPOSE: Stereotactic ablative body radiotherapy (SABR) is a novel option to treat primary renal cell carcinoma. However, a high radiation dose may be received by the treated kidney, which may affect its function posttreatment. This study investigates the dose-effect relationship of kidney SABR with posttreatment renal function. METHODS AND MATERIALS: This was a prespecified secondary endpoint of the multicenter FASTRACK II (Focal Ablative STereotactic RAdiotherapy for Cancers of the Kidney phase II) clinical trial (National Clinical Trial 02613819). Patients received either 26 Gy in a single fraction (SF) for tumors with a maximal diameter of 4 cm or less or 42 Gy in 3 fractions (multifraction [MF]) for larger tumors. To determine renal function change, 99mTc-dimercaptosuccinic acid (DMSA) single-photon emission computed tomography/computed tomography (SPECT/CT) scans were acquired, and the glomerular filtration rate was estimated at baseline, 12, and 24 months posttreatment. Imaging data sets were rigidly registered to the planning CT where kidneys were segmented to calculate dose-response curves. RESULTS: From 71 enrolled patients, 36 (51%) and 26 (37%) patients were included in this study based on availability of posttreatment data at 12 and 24 months, respectively. The ipsilateral kidney glomerular filtration rate decreased from baseline by 42% and 39% in the SF cohort and by 45% and 62% in the MF cohort, at 12 and 24 months, respectively (P < .03). The loss in renal function was 3.6%/Gy ± 0.8%/Gy and 4.5%/Gy ± 1.0%/Gy in the SF cohort and 1.7%/Gy ± 0.1%/Gy and 1.7%/Gy ± 0.2%/Gy in the MF cohort at 12 and 24 months, respectively. The major loss in renal function occurred in high-dose regions, where dose-response curves converged to a plateau. CONCLUSIONS: For the first time in a multicenter study, the dose-effect relationship at 12 and 24 months post-SABR treatment for primary renal cell carcinoma was quantified. Kidney function reduces linearly with dose up to 100 Gy BED3.
RESUMEN
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.
