Purpose: 3'-[F-18]Fluoro-3'-deoxythymidine (FLT) is an analog of thymidine that is being developed for imaging cellular proliferation. The goal of this study was to prove that the dose of FLT used for positron emission tomography imaging produces no significant toxicity.
Procedures: Twelve patients with gliomas with either recurrence or suspected radionecrosis were imaged with FLT. Before and at several time points after imaging, subjects underwent general physical and neurological examinations with review of systems and tests of hematologic, hepatic, renal, and several other metabolic parameters. Vital signs and electrocardiograms were monitored during and after the imaging session.
Results: There were no significant adverse effects from FLT injected at a dose of 0.07 mCi/kg (maximum of 5 mCi) at specific activities of 1.25 Ci/micromol or higher. The FLT mass administered for imaging was 0.0001% to 0.0009% of the least toxic cumulative dose administered in clinical trials of FLT as an antiretroviral agent.
Conclusions: FLT is a safe radiotracer for quantifying proliferation in the human cancer setting.