%0 Personal Communication %A Ceccon, Garry %A Lohmann, Philipp %A Tscherpel, Caroline %A Dunkl, Veronika %A Rapp, Marion %A Stoffels, Gabriele %A Herrlinger, Ulrich %A Rosen, Jurij %A Wollring, Michael %A Shah, Nadim J %A Fink, Gereon R %A Langen, Karl-Josef %A Galldiks, Norbert %T NIMG-79. EARLY TREATMENT RESPONSE ASSESSMENT USING O-(2-18F-FLUOROETHYL)-L-TYROSINE (FET) PET COMPARED TO MRI IN MALIGNANT GLIOMAS TREATED WITH ADJUVANT TEMOZOLOMIDE CHEMOTHERAPY %@ 1523-5866 %M FZJ-2022-02459 %D 2018 %X AbstractBACKGROUNDThe goal of this prospective study was to compare the value of conventional MRI and O-(2-18F-fluoroethyl)-L-tyrosine (FET) PET for response assessment in patients with malignant glioma treated with first-line adjuvant temozolomide chemotherapy (TMZ).METHODSAfter biopsy/resection and completion of radiotherapy with concomitant temozolomide, 34 malignant glioma patients (glioblastoma, n=31; IDH-wildtype anaplastic astrocytoma, n=2; H3K27-mutated midline glioma, n=1) (age range, 20–66 years) were subsequently treated with adjuvant TMZ (5/28). FET-PET scans were performed at baseline and after 10–12 weeks. The first follow-up MRI after radiotherapy (9 ± 3 weeks) was compared with the early postoperative MRI. We obtained FET metabolic tumor volumes (MTV) and tumor/brain ratios (TBR). Threshold values of FET-PET parameters for treatment response were established by ROC analyses using the progression-free survival (PFS) ≤/>9 months as reference. MRI response assessment was based on RANO criteria. The predictive ability of FET-PET thresholds and MRI changes on early response assessment was evaluated subsequently concerning PFS using univariate survival estimates.RESULTSRelative TBR changes were not predictive for a PFS>9 months (P>0.05), whereas the absolute MTV at follow-up significantly predicted a PFS>9 months (P=0.016; threshold, 14.5 ml). The relative MTV change enabled the most significant PFS prediction. Responders defined by relative MTV changes (threshold, ≤0%) had a significantly 2-fold longer PFS than non-responders (16 vs. 8 months, P=0.003). RANO criteria at the first follow-up MRI after radiotherapy were not predictive for a PFS>9 months (P=0.260). CONCLUSIONS: FET-PET appears to be useful for identifying responders to adjuvant TMZ early after treatment initiation. %F PUB:(DE-HGF)4 %9 Communication %R 10.1093/neuonc/noy148.801 %U https://juser.fz-juelich.de/record/908208