Discrepant MR and [(18)F]Fluoroethyl-L-Tyrosine PET Imaging Findings in a Patient with Bevacizumab Failure.

Antiangiogenic treatment using bevacizumab may cause difficulties in distinguishing between antivascular and true antitumor effects when using MRI response criteria based on changes of contrast enhancement (i.e., Macdonald criteria). Furthermore, more precise tumor response assessment criteria (i.e., RANO criteria), which incorporate nonenhancing T2/FLAIR sequences into Macdonald criteria, may be influenced by other causes of T2/FLAIR hyperintensity (e.g., radiation-induced gliosis). The authors present discrepant MR and [(18)F]fluoroethyl-L-tyrosine PET imaging findings in a patient with bevacizumab treatment failure.