JS08.5.A AMINO-ACID PET VERSUS MRI GUIDED RE-IRRADIATION IN PATIENTS WITH RECURRENT GLIOBLASTOMA - GLIAA TRIAL (NOA 10/ARO 2013-1, DKTK-A)

Abstract BACKGROUND This trial aimed to investigate whether re-irradiation based on (O-(2-Fluoroethyl)-L-tyrosine, FET)-positron emission tomography (PET) leads to an improvement in progression-free survival (PFS) in patients with recurrent glioblastoma (rGBM), compared to a target volume delineation based on contrast-enhanced T1-weighted MRI (T1Gd-MRI). MATERIAL AND METHODS GLIAA was a prospective, multicenter, randomized clinical trial (NOA 10/ARO 2013-1, DKTK-a., NCT01252459). Patients with rGBM of 1-6 cm were randomized 1:1 at 14 centers in Germany between a FET-PET- and a T1Gd-MRI-based target volume delineation. The RT was performed with 3 Gy/d, 5x/week, to a total dose of 39 Gy. All patients had been previously irradiated with 59.4-60Gy at least 6 months before study treatment and had a histologically confirmed rGBM with a diameter of 1 - 6 cm on both FET-PET and T1Gd-MRI. The primary end point was PFS. Secondary end points included overall survival (OS), locally controlled survival, assessment of delineated volumes, topography of progression, rate of radiation necrosis after re-irradiation, and safety of FET-application in PET imaging. RESULTS Between November 2013 and September 2021, 200 patients were randomized between FET-PET-based (n=100) and GdT1-MRI-based (n=100) target volume delineation. A total of n=98 and n=97 patients, respectively, were treated per protocol. Median PFS was 4.0 months (95% confidence interval [CI] 3.7-5.2) in the FET-PET arm and 4.9 months (95% CI 3.7-6.0) in the GdT1-MRI arm (one-sided stratified log-rank test p=0.98; adjusted HR for the experimental versus the control arm 1.14 [95% CI 0.85-1.52], p=0.39;). Median OS was 9.4 months (95% CI 7.8-11.1) in the FET-PET arm and 9.0 months (95% CI 7.6-10.5) in the GdT1-MRI arm (HR 1.01 [95% CI 0.75-1.37], p=0.92). Median LCS was 6.3 months (95% CI 5.1-7.2) in the FET-PET arm and 6.8 months (95% CI 6.2-7.3) in the GdT1-MRI arm (HR 1.20 [95% CI 0.88-1.62], p=0.25). At 12 months, the local control rate was 22% in the FET-PET arm (95% CI 14%-31%) and 20% in the GdT1-MRI arm (95% CI 12%-29%). In the PET arm, 45.0% of recurrences were in field, 28.3% out of field, and 21.7% marginal. In the MRI arm, 47.4% relapsed in field, 31.6% out of field, and 14.0% marginal. 25.5% of patients in the FET-PET arm and 21.6% in the GdT1-MRI arm had a documented radiation necrosis. There were no adverse events related to the application of the FET tracer. CONCLUSION This is the first randomized tria