The Prognostic Value of O-(2-18F-fluoroethyl)-L-tyrosine positron emission tomography (FET-PET) at Radiotherapy Planning in Newly Diagnosed Glioblastoma

182 Objectives Despite aggressive therapy, glioblastoma (GBM) patients show a great variability in progression free survival (PFS) and overall survival (OS). O-(2-18F-fluoroethyl)-L-tyrosine (FET) PET has been shown to increase the accuracy of delineating tumor tissue. To improve treatment stratification we wished to explore the potential of FET PET as an independent prognostic biomarker. Methods We retrospectively analyzed 146 consecutively treated patients at our institute. All patients were treated with temozolomide and radiation therapy (RT). CT/MR and FET PET scans were obtained for RT planning. We used Cox proportional hazards models with OS and PFS as endpoints, to test the prognostic value of FET PET biological tumor volume (BTV), as well as maximum and mean tumor-to-background ratio (TBRmax and TBRmean) Results Median follow-up time was 14 months, median OS and PFS was 16.5 and 6.5 months respectively. In multivariate analysis increasing BTV (HR=1.16; 95%CI: 1.07-1.25; P Conclusions Large BTV on FET PET for RT planning is an independent prognostic factor of poor OS and PFS in GBM patients. With the introduction of FET PET, we obtain a prognostic index that can help in GBM treatment stratification.