title: MRI and 11C-methyl-L-methionine PET Differentiate Bevacizumab True Responders After Initiating Therapy for Recurrent Glioblastoma.
abstract: OBJECTIVE
  Normalization of tumor vasculature after administering bevacizumab (BEV) makes assessment of therapeutic response using MRI difficult. The aim of this study was to clarify whether PET with C-methyl-L-methionine (MET-PET) would supplement MRI assessing of response after initiating BEV in glioblastoma.
  
  
  METHODS
  Twenty patients with recurrent glioblastoma were treated with biweekly BEV plus temozolomide. Both MRI and MET-PET were performed before treatment (baseline) and at 4 and 8 weeks after starting treatment. Results on MRI (response or nonresponse) were compared with those on MET-PET, with response defined as a tumor-to-normal brain ratio of SUV (SUVT/N) of less than 1.6. Progression-free survival (PFS) was compared between responders and nonresponders on MRI alone and MET-PET alone. Progression-free survival was also compared between patients showing response on both MRI and MET-PET and patients showing response on MRI but nonresponse on MET-PET at each time point.
  
  
  RESULTS
  PFS was significantly longer in responders than nonresponders on both MRI at 4 and 8 weeks and MET-PET at 8 weeks, whereas MET-PET at 4 weeks provided no information regarding outcomes. Combined assessment with MRI and MET-PET at 4 weeks was not provide predictive of PFS, whereas patients showing response on both modalities (true responders) at 8 weeks exhibited significantly longer PFS than did patients showing response on MRI but nonresponse on MET-PET (pseudoresponders).
  
  
  CONCLUSIONS
  Combined assessment with MRI and MET-PET at 8 weeks can differentiate true responders who are predicted to show more favorable prognosis from pseudoresponders.
authors.affiliation: From the *Department of Neurosurgery, †Cyclotron Research Center, ‡Department of Radiology, and §Institute for Biomedical Sciences, Iwate Medical University, Iwate, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Beppu
authors.forename: Kazunori
authors.initials: K
authors.lastname: Terasaki
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Sasaki
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sato
authors.forename: Makiko
authors.initials: M
authors.lastname: Tomabechi
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kato
authors.forename: Makoto
authors.initials: M
authors.lastname: Sasaki
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Ogasawara
mesh_terms: D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D000068258:Bevacizumab / Q000008:administration & dosage; D001932:Brain Neoplasms / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000188:drug therapy; D003606:Dacarbazine / Q000008:administration & dosage / Q000031:analogs & derivatives; D018572:Disease-Free Survival; D005260:Female; D005909:Glioblastoma / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000188:drug therapy; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008715:Methionine / Q000031:analogs & derivatives; D008875:Middle Aged; D064847:Multimodal Imaging; D009364:Neoplasm Recurrence, Local / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000188:drug therapy; D009389:Neovascularization, Pathologic / Q000000981:diagnostic imaging* / Q000188:drug therapy; D049268:Positron-Emission Tomography; D011379:Prognosis; D000077204:Temozolomide; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000068258:Bevacizumab; D003606:Dacarbazine; D008715:Methionine; C038344:methionine methyl ester; D000077204:Temozolomide