Visual and semiquantitative C-11-methionine PET: an independent prognostic factor for survival of newly diagnosed and treatment-naive gliomas

Background. Few data exist regarding the prognostic value of L-[S-methyl-C-11] methionine (MET) PET for treatment-naive gliomas. Methods. A total of 160 glioma patients (89 men, 71 women; mean age: 45, range 18-84 y) underwent a MET PET prior to any therapy. The PET scans were evaluated visually and semiquantitatively by tumor-to-background (T/N) ratio thresholds chosen by analysis of receiver operating characteristics. Additionally, isocitrate dehydrogenase 1-R132H (IDH1-R132H) immunohistochemistry was performed. Survival analysis was done using Kaplan-Meier estimates and the Cox proportional hazards model. Results. Significantly shorter mean survival times (7.2 vs 8.6 y; P = 0.024) were seen in patients with amino acid avid gliomas (n = 137) compared with visually negative tumors (n = 33) in MET PET. T/N ratio thresholds of 2.1 and 3.5 were significantly associated with survival (10.3 vs 7 vs 4.3 y; P < 0.001). Mean survival differed significantly using the median T/N ratio of 2.4 as cutoff, independent of histopathology (P < 0.01; mean survival: 10.2 +/- 0.8 y vs 5.5 +/- 0.6 y). In the subgroup of 142 glioma patients characterized by IDH1-R132H status, MET T/N ratio demonstrated a significant prognostic impact in IDH1-R132H wildtype astrocytomas and glioblastoma (P = 0.001). Additionally, multivariate testing revealed semiquantitative MET PET as an independent prognostic parameter for treatment-naive glioma patients without (P = 0.031) and with IDH1-R132H characterization of gliomas (P = 0.024; odds ratio 1.57). Conclusion. This retrospective analysis demonstrates the value of MET PET as a prognostic parameter on survival in treatment-naive glioma patients.