RT Journal Article SR Electronic T1 Quantitative analysis of blood-borne 18F-FMISO metabolites in cancer patients by HPLC using an integrated high-sensitivity coincidence detector JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1289 OP 1289 VO 56 IS supplement 3 A1 Zhang, Hanwen A1 Carlin, Sean A1 Zanzonico, Pat A1 Schoder, Heiko A1 Lee, Nancy A1 Schwartz, Jazmin A1 Grkovski, Milan A1 Staton, Kevin A1 Humm, John A1 Nehmeh, Sadek YR 2015 UL http://jnm.snmjournals.org/content/56/supplement_3/1289.abstract AB 1289 Objectives Tumor hypoxia has been shown to be of value in predicting treatment response. Kinetic analysis (for derivation of the trapping rate) of 18F-fluoromisonidazole (18F-FMISO) PET imaging has been proposed as a more reliable approach than “late” static imaging for identificating status of tumor hypoxia. This necessitates correcting for any metabolite(s) in the FMISO input function. The aim of this study is to assess the amount of FMISO metabolites in plasma.Methods Blood samples of 10 patients undergoing 18F-FMISO PET studies were collected at 45, 90, or 180 min post-injection (pi) and the activity in whole blood, serum, protein-precipitated pellet, and protein-free supernatant were assayed using a gamma counter. After filtration with 0.45 μm filter and removal of acetonitrile by evaporation, the potential metabolites in the supernatant were determined with HPLC system that was integrated with an in-line high-sensitivity coincidence detector.Results The activity concentrations in whole blood and in plasma were very early equal at all times, indicating that 18F-FMISO is freely exchangeable between the plasma and blood cells, as expected. Following the acetonitrile precipitation of the serum, the radioactivity was nearly quantitatively recovered in the supernatant (89-95%). All patient studies showed that up to 3 h pi, there was no detectable metabolite peak in the precipitated supernatant by HPLC; only a single peak, which corresponded to the intact 18F-FMISO, was observed at an elution time of 13 min.Conclusions 18F-FMISO is metabolically stable during circulation and most of the injected radiotracer in the blood remains available intact to cancer cells.Research Support Supported by NIH grant P50-CA84638 and NIH grant 1U01CA157442-01A1.