Prognostic value of FET-PET after interstitial brachytherapy in patients with recurrent high grade glioma

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1232 Objectives Therapy monitoring in glioma patients after interstitial I-125 brachytherapy remains challenging because posttherapeutic changes in MRI, such as contrast enhancement, can mimic tumor progression. The aim of this study was to evaluate the prognostic value of serial FET-PET scans and the differentiation between posttherapeutic changes and tumor progression after interstitial brachytherapy. Methods 34 patients with recurrent high grade glioma treated with interstitial brachytherapy were included. Serial PET scans were performed before treatment as well as for subsequent treatment monitoring. Maximal tumoral uptake (SUVmax/BG), tumor volume and kinetic analysis were evaluated. PET findings were correlated with clinical follow-up. In case of suspected tumor progression or recurrence, histological confirmation was performed by means of biopsy. Results The median progression free survival (PFS) of the patients was 11.1 months during a median follow-up of 17.0 months. 15 patients presented with local tumor progression (44 %) within the first 12 months. Kinetic analysis predicted PFS during the first year after brachytherapy. PET findings such as SUVmax/BG and tumor volume did not allow any prognosis in the early evaluation 3 months after seed implantation. Yet, tumor volume at 6 months showed significant differences between patients with and without local tumor progression (p Conclusions FET-PET seems to be a sensitive tool for treatment monitoring in patients with recurrent high grade glioma after interstitial brachytherapy. Additional assessment of FET-kinetics enables a more accurate treatment evaluation, even in early posttherapeutic PET scan (after 3 months) and was shown to be predictive for disease course. Changes in tumor volume as well as SUVmax/BG alone did not allow an accurate treatment assessment in the early PET scan, but at the 6 months examination. This might be due to unspecific early therapy induced increase of FET-uptake

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