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

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 (K₁), and phosphorylation (k₃). FDG-PET scans were obtained 75-90 min postinjection. Results: K_FLT and k₃, but not K₁ or k₃/k₂+k₃, 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.