NIMG-34THE PROGNOSTIC VALUE OF POSTOPERATIVE O-(2-18F-FLUOROETHYL)-L-TYROSINE POSITRON EMISSION TOMOGRAPHY IN NEWLY DIAGNOSED GLIOBLASTOMA

Abstract

BACKGOUND: Patients with glioblastoma (GBM) show a variable disease course ranging from rapid progression to prolonged progression free survival (PFS). Despite aggressive standard therapy consisting of radiotherapy plus concomitant and adjuvant temozolomide (RCX) the prognoses is poor with a median overall survival (OS) less than 15 months and 5-year overall survival less than 10%. To maximize patient survival and optimize quality of life, it is relevant to identify prognostic biomarkers for treatment stratification. Positron emission tomography (PET) scanning using radiolabeled amino acids has been introduced in the radiation therapy planning of GBM. Therefore this study will evaluate whether postoperative FET PET in newly diagnosed GBM can provide additional prognostic information on outcome. MATERIALS AND METHODS: 147 patients from our GBM database treated with RCX and evaluated with FET PET postoperatively (1-2 weeks) in the period November 2011 - February 2014 were included retrospectively. With OS as the primary endpoint, and PFS as a secondary endpoint, the prognostic value of postoperative biological tumor volume (BTV) in FET PET, mean tumor to background ratio (TBRmean) and maximum tumor to background ratio (TBRmax) was estimated using Cox proportional hazards model. The analysis was adjusted for the known prognostic factors, performance status (PS), age and corticosteroid therapy status, by multivariate analysis. RESULTS: Median OS and PFS were 14.0 and 6.54 months respectively. In the univariate analysis, increasing BTV and higher values of TBRmean and TBRmax correlated significantly (<0.0001) with poor OS and PFS. In the multivariate analysis increasing BTV, poor PS and high age was independent prognostic factors for poor OS and PFS with p-values < 0.0001. CONCLUSION: Increasing postoperative FET PET tumor volume is an important independent prognostic factor of poor OS and PFS for GBM patients. Underlining the importance, of maximal tumor resection, on OS.