NCI-Sponsored Trial for the Evaluation of Safety and Preliminary Efficacy of 3′-Deoxy-3′-[18F]fluorothymidine (FLT) as a Marker of Proliferation in Patients with Recurrent Gliomas: Preliminary Efficacy Studies

Abstract

Purpose 3′-Deoxy-3′-[¹⁸F]fluorothymidine ([¹⁸F]FLT) is being developed for imaging cellular proliferation. The goals were to explore the capacity of FLT-positron emission tomography (PET) to distinguish between recurrence and radionecrosis in gliomas and compare the results to those obtained with 2-fluoro-2-deoxy-d-glucose (FDG). Procedures Fifteen patients with tumor recurrence and four with radionecrosis, determined by clinical course and magnetic resonance imaging results, were studied by dynamic [¹⁸F]FLT-PET with arterial blood sampling. A two-tissue compartment four-rate constant model was used to determine metabolic flux (K _FLT), blood to tissue transport (K ₁), and phosphorylation (k ₃). FDG-PET scans were obtained 75–90 min postinjection. Results K _FLT and k ₃, but not K ₁ or k ₃/k ₂ + k ₃, reached significance for separating the recurrence from radionecrosis groups. Standardized uptake value and visual analyses of FLT or FDG images did not reach significance. Conclusions K _FLT (flux) appears to distinguish recurrence from radionecrosis better than other parameters, FLT and FDG semiquantitative approaches, or visual analysis of images of either tracer.