Prognostic value of early [18F]fluoroethyltyrosine positron emission tomography after radiochemotherapy in glioblastoma multiforme.

PURPOSE

Early detection of treatment response in glioma patients after radiochemotherapy (RCX) is uncertain because treatment-related contrast enhancement in magnetic resonance imaging can mimic tumor progression. Positron emission tomography (PET) using the amino acid tracer [(18)F]fluoroethyltyrosine (FET) seems to be a promising tool for treatment monitoring. The aim of this prospective study was to evaluate the prognostic value of early changes of FET uptake after postoperative RCX in glioblastomas.

METHODS AND MATERIALS

Twenty-two patients with glioblastoma were treated by surgery and subsequent RCX (whole dose 60-72 Gy). The FET-PET studies were performed before RCX, 7-10 days and 6-8 weeks after completion of RCX. Early treatment response in PET was defined as a decrease of the maximal tumor-to-brain ratio (TBR(max)) of FET uptake after RCX of more than 10%. The prognostic value of early changes of FET uptake after RCX was evaluated using Kaplan-Maier estimates for median disease-free survival and overall survival.

RESULTS

The median overall and disease-free survival of the patients was 14.8 and 7.8 months. There were 16 early responders in FET-PET (72.7%) and 6 nonresponders (27.3%). Early PET responders had a significantly longer median disease-free survival (10.3 vs. 5.8 months; p < 0.01) and overall survival ("not reached" vs. 9.3 months; p < 0.001). No statistically significant differences between the patient subgroups were found concerning the defined prognostic parameters.

CONCLUSIONS

FET-PET is a sensitive tool to predict treatment response in patients with glioblastomas at an early stage after RCX.