RADT-21. DUAL FET PET-GUIDED SIB IN RADIOTHERAPY OF NEWLY DIAGNOSED GLIOBLASTOMA - A PILOT STUDY

Abstract

Abstract BACKGROUND PET using FET is a valuable tool to determine the actual glioblastoma infiltration.The FET-PET examination can be performed using the dual-time point acquisition of FET . Infiltration defined in dual FET PET corresponds to the location and shape of the recurrence. The aim of this study was to evaluate safety and efficacy of simultaneous integrated boost based on dual FET PET combined with temozolomide TMZ for the postoperative treatment of GBM. METHODS AND MATERIALS In a prospective pilot study, 17 patients were enrolled. All patient presented an active tumor in postoperative PET imaging. The radiotherapy was performed as an FET-PET-based integrated-boost IMRT. The prescribed dose was 78 and 60 Gy (single dose 2.6 and 2.0 Gy, respectively). The progression-free survival (PFS) and overall survival (OS), toxicities and radiation necrosis rate were evaluated. RESULTS The median follow up was 37 months.Two patients were found to have uncontrolled seizures during radiation treatment and were not able to received treatment per protocol. Patients treated per protocol presented new or increased neurological deficits in 7/15 cases in a month after irradiation. In 4 patients radiation necrosis was confirmed in pathological report after re-surgery. Three patients were still alive after 26,28 and 38 months of follow up without progression and any signs of treatment related late toxicity. The 2-year survival rate was 43% in all patients treated per protocol. Median overall survival (OS) and disease-free survival (DFS) were 20 and 12 months, respectively. In a subgroup of MGMT methylated and unmethylated the median survival was 25 and 12 months. CONCLUSIONS Our dose escalation concept with a total dose of 78 Gy, based on FET-PET, have lead to promising survival results even within MGMT unmethylated subgroup. However rate of early toxicity and radiation necrosis is high.