[18F-fluorothymidine preclinical study in non-human primate. Dosimetry and biodistribution]

Positron emission tomography-computed tomography (PET-CT) is part of the new diagnostic and therapeutic algorithms for Hodgkin lymphoma. PET-CT is a valuable tool for the assessment of treatment response and prognosis, both by means of interim PET-CT with 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) as well as end of treatment (EOT) PET-CT. Given the low specificity of [18F]FDG for the diffuse large B cell lymphoma (DLBCL), there is an emerging need for a more specific radiopharmaceutical agent. The recent approval of the radiotracer 3'-deoxy-[18F]-3'-flourothymidine ([18F]FLT), a phase-S mitosis cell proliferation marker, for clinical application in our country, shows as a promising radiopharmaceutical for diagnostic use with incremental value over [18F]FDG. In this study, non-human primates (Sapajus cay) were studied. PET-CT study was performed after the injection of [18F]FLT. Whole-body images were obtained to evaluate the biodistribution and to calculate the dosimetry of bone marrow, as this is a critic organ to this radiotracer. Time-activity curves were traced, normalized activity uptake of the organs of interest were calculated, and mean absorbed dose was also calculated using the established Medical Internal Radiation Dosimetry (MIRD) scheme. The mean dose obtained in the animal model per unit of activity administered was 8.7 uGy/MBq. This result was extrapolated to an adult human model resulting in 32 uGy/MBq, thereby suggesting that [18F]FLT is a secure diagnostic tool to be used on the tracing of patients with DLBCL.