Assessment of 18F-FET PET-based response in patients with gliomas using the PET RANO 1.0 criteria.

Background: We evaluated the amino acid PET-based response assessment criteria (PET RANO 1.0) for their proficiency in predicting longer survival in patients with gliomas undergoing adjuvant temozolomide chemotherapy. Methods: In a previous study, 38 patients with newly diagnosed grade 4 gliomas according to the World Health Organisation classification underwent O-(2-[18F]fluoroethyl)-l-tyrosine (18F-FET) PET at baseline and after the second cycle of adjuvant temozolomide chemotherapy. The ability of PET parameter changes to predict favorable progression-free and overall survival (PFS, OS) of ≥9 and ≥15 months was evaluated. Here, we performed a post hoc analysis of these PET data to evaluate the PET RANO 1.0 criteria. In addition, the value of the RANO 2.0 criteria for MRI to predict response was evaluated and compared with the PET RANO 1.0 criteria. Results: According to the PET RANO 1.0 criteria, patients with Stable Disease (n = 16), Partial Response (n = 9), or Complete Response (n = 0) had a significantly longer OS than patients with Progressive Disease (n = 13) (16.8 vs 12.0 months; P = .016). This difference remained significant in the multivariate survival analysis (HR, 4.185; 95% CI, 1.715-10.530, P = .002). In contrast, PFS was not significantly different between the two groups (9.7 vs 8.1 months; P = .147). PET RANO 1.0 criteria could not identify patients with a PFS ≥ 9 months (P = .503) or OS ≥ 15 months (P = .722). RANO 2.0 criteria for MRI were unable to predict a longer PFS (8.8 vs 9.8 months; P = .565) or OS (16.4 vs 16.8 months; P = .625). Conclusions: Our data suggest that PET RANO 1.0 criteria identify survival differences between predefined groups.