Flare Phenomenon in O-(2-18F-Fluoroethyl)-l-Tyrosine PET After Resection of Gliomas

Christian P. Filss, Ann K. Schmitz, Gabriele Stoffels, Carina Stegmayr, Philipp Lohmann, Jan Michael Werner, Michael Sabel, Marion Rapp, Roland Goldbrunner, Bernd Neumaier, Felix M. Mottaghy, N. Jon Shah, Gereon R. Fink, Norbert Galldiks, Karl-Josef Langen*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


PET using O-(2-F-18-fluoroethyl)-L-tyrosine (F-18-FET) is useful to detect residual tumor tissue after glioma resection. Recent animal experiments detected reactive changes in F-18-FET uptake at the rim of the resection cavity within the first 2 wk after resection of gliomas. In the present study, we evaluated pre- and postoperative F-18-FET PET scans of glioma patients with particular emphasis on the identification of reactive changes after surgery. Methods: Forty-three patients with cerebral gliomas (9 low-grade, 34 high-grade; 9 primary tumors, 34 recurrent tumors) who had preoperative (time before surgery: median, 23 d; range, 6-44 d) and postoperative F-18-FET PET (time after surgery: median, 14 d; range, 5-28 d) were included. PET scans (20-40 min after injection) were evaluated visually for complete or incomplete resection and compared with MRI. Changes in F-18-FET uptake were evaluated by tumor-to-brain ratios in residual tumor and by maximum lesion-to-brain ratios near the resection cavity. Results: Visual analysis of F-18-FET PET scans revealed complete resection in 16 of 43 patients and incomplete resection in the remaining patients. PET results were concordant with MRI in 69% of the patients. The maximum lesion-to-brain ratio for F-18-FET uptake near the resection cavity was significantly higher than preoperative values (1.59 +/- 0.36 vs. 1.14 +/- 0.17; n = 43; P <0.001). In 11 patients (26%), a flare phenomenon was observed, with a considerable increase in F-18-FET uptake compared with preoperative values in either the residual tumor (n = 5) or areas remote from the tumor on the preoperative PET scan (n = 6) (2.92 +/- 1.24 vs. 1.62 +/- 0.75; P <0.001). Further follow-up in 5 patients showed decreasing F-18-FET uptake in the flare areas in 4 patients and progress in 1 patient. Conclusion: Our study confirmed that F-18-FET PET provides valuable information for assessing the success of glioma resection. Postoperative reactive changes at the rim of the resection cavity appear to be mild. However, in 23% of the patients, a postoperative flare phenomenon was observed that warrants further investigation.

Original languageEnglish
Pages (from-to)1294-1299
Number of pages6
JournalJournal of Nuclear Medicine
Issue number9
Publication statusPublished - 1 Sept 2020


  • brain tumor surgery
  • amino acid PET
  • FET
  • treatment-related changes
  • extent of resection


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