Bioassay-derived dosimetry of 6-deoxy-6-[18-F]fluoro-D-fructose, a PET tracer for GLUT5 imaging

Objectives 6-deoxy-6-[18-F]fluoro-D-fructose (6-[18F]FDF) was developed as a PET radiotracer for imaging GLUT5-expressing breast cancer in vivo. This study aimed at obtaining human normal organ dosimetry estimates for this novel radiotracer by means of rat bioassays, as a prerequisite for a first study in man.

Methods Sprague-Dawley rats were injected into the tail vein with 15...17 MBq of 6-[18-F]FDF and sacrificed at 5, 30, 60, 120, 180, 240 and 360 minutes post injections. Biodistribution at these time points was determined using an NaI well counter. Furthermore, PET measurements were performed on a small animal PET scanner (Concorde microPET R4). The experimental data obtained from the biodistribution served as the basis for the allometric extrapolation to the standard man anatomic model and normal organ-absorbed dose calculations using OLINDA/EXM (Vanderbilt University) software.

Results The human effective dose determined for 6-[18F]FDF was 0.0085 mSv/MBq and 0.010 mSv/MBq for the adult human male and female phantom, respectively. The highest organ doses occurred in the osteogenic cells with a dose equivalent of 0.029 mSv/MBq and 0.038 mSv/MBq in a human male and female, respectively. An injected activity of 370 MBq (10 mCi) of 6-[18-F]FDF would expose an adult human male and female to an effective radiation dose of 3.1 mSv and 3.7 mSv, respectively, values generally comparable to clinically used PET radiopharmaceuticals.

Conclusions This study presents the first calculated human dose estimates for 6-[18-F]FDF based on biodistribution in normal, healthy rats. The animal-based estimation of human radiation doses supports a clinical trial of 6-[18-F]FDF in humans.