Diagnosis of pseudoprogression in patients with glioblastoma using O-(2-[18F]fluoroethyl)-L-tyrosine PET.

Abstract

PURPOSE:

The follow-up of glioblastoma patients after radiochemotherapy with conventional MRI can be difficult since reactive alterations to the blood-brain barrier with contrast enhancement may mimic tumour progression (i.e. pseudoprogression, PsP). The aim of this study was to assess the clinical value of O-(2-(18)F-fluoroethyl)-L-tyrosine ((18)F-FET) PET in the differentiation of PsP and early tumour progression (EP) after radiochemotherapy of glioblastoma.

METHODS:

A group of 22 glioblastoma patients with new contrast-enhancing lesions or lesions showing increased enhancement (>25 %) on standard MRI within the first 12 weeks after completion of radiochemotherapy with concomitant temozolomide (median 7 weeks) were additionally examined using amino acid PET with (18)F-FET. Maximum and mean tumour-to-brain ratios (TBRmax, TBRmean) were determined. (18)F-FET uptake kinetic parameters (i.e. patterns of time-activity curves, TAC) were also evaluated. Classification as PsP or EP was based on the clinical course (no treatment change at least for 6 months), follow-up MR imaging and/or histopathological findings. Imaging results were also related to overall survival (OS).

RESULTS:

PsP was confirmed in 11 of the 22 patients. In patients with PsP, (18)F-FET uptake was significantly lower than in patients with EP (TBRmax 1.9 ± 0.4 vs. 2.8 ± 0.5, TBRmean 1.8 ± 0.2 vs. 2.3 ± 0.3; both P < 0.001) and presence of MGMT promoter methylation was significantly more frequent (P = 0.05). Furthermore, a TAC type II or III was more frequently present in patients with EP (P = 0.04). Receiver operating characteristic analysis showed that the optimal (18)F-FET TBRmax cut-off value for identifying PsP was 2.3 (sensitivity 100 %, specificity 91 %, accuracy 96 %, AUC 0.94 ± 0.06; P < 0.001). Univariate survival analysis showed that a TBRmax <2.3 predicted a significantly longer OS (median OS 23 vs. 12 months; P = 0.046).

CONCLUSION:

(18)F-FET PET may facilitate the diagnosis of PsP following radiochemotherapy of glioblastoma.

• Authors: Norbert Galldiks, Veronika Dunkl, Gabriele Stoffels, Markus Hutterer, Marion Rapp, Michael Sabel, Guido Reifenberger, Sied Kebir, Franziska Dorn, Tobias Blau, Ulrich Herrlinger, Peter Hau, Maximilian I Ruge, Martin Kocher, Roland Goldbrunner, Gereon R Fink, Alexander Drzezga, Matthias Schmidt, Karl-Josef Langen
• Journal: European journal of nuclear medicine and molecular imaging (Eur J Nucl Med Mol Imaging) Vol. 42 Issue 5 Pg. 685-95 (Apr 2015) ISSN: 1619-7089 [Electronic] Germany
• PMID: 25411133 (Publication Type: Journal Article)

Chemical References

• O-(2-fluoroethyl)tyrosine
• Radiopharmaceuticals
• Tyrosine

Topics

• Adult
• Aged
• Brain Neoplasms (diagnostic imaging)
• Disease Progression
• False Positive Reactions
• Female
• Glioblastoma (diagnostic imaging)
• Humans
• Male
• Middle Aged
• Positron-Emission Tomography
• Radiopharmaceuticals
• Tyrosine (analogs & derivatives)