Comparisons of [18F]-1-deoxy-1-fluoro-scyllo-inositol with [18F]-FDG for PET imaging of inflammation, breast and brain cancer xenografts in athymic mice

Abstract

Introduction: The aim of the study was to evaluate the uptake of [(18)F]-1-deoxy-1-fluoro-scyllo-inositol ([(18)F]-scyllo-inositol) in human breast cancer (BC) and glioma xenografts, as well as in inflammatory tissue, in immunocompromised mice. Studies of [(18)F]-2-fluoro-2-deoxy-d-glucose ([(18)F]-FDG) under the same conditions were also performed.

Methods: Radiosynthesis of [(18)F]-scyllo-inositol was automated using a commercial synthesis module. Tumour, inflammation and normal tissue uptakes were evaluated by biodistribution studies and positron emission tomography (PET) imaging using [(18)F]-scyllo-inositol and [(18)F]-FDG in mice bearing subcutaneous MDA-MB-231, MCF-7 and MDA-MB-361 human BC xenografts, intracranial U-87 MG glioma xenografts and turpentine-induced inflammation.

Results: The radiosynthesis of [(18)F]-scyllo-inositol was automated with good radiochemical yields (24.6%±3.3%, uncorrected for decay, 65±2 min, n=5) and high specific activities (≥195 GBq/μmol at end of synthesis). Uptake of [(18)F]-scyllo-inositol was greatest in MDA-MB-231 BC tumours and was comparable to that of [(18)F]-FDG (4.6±0.5 vs. 5.5±2.1 %ID/g, respectively; P=.40), but was marginally lower in MDA-MB-361 and MCF-7 xenografts. Uptake of [(18)F]-scyllo-inositol in inflammation was lower than [(18)F]-FDG. While uptake of [(18)F]-scyllo-inositol in intracranial U-87 MG xenografts was significantly lower than [(18)F]-FDG, the tumour-to-brain ratio was significantly higher (10.6±2.5 vs. 2.1±0.6; P=.001).

Conclusions: Consistent with biodistribution studies, uptake of [(18)F]-scyllo-inositol was successfully visualized by PET imaging in human BC and glioma xenografts, with lower accumulation in inflammatory tissue than [(18)F]-FDG. The tumour-to-brain ratio of [(18)F]-scyllo-inositol was also significantly higher than that of [(18)F]-FDG for visualizing intracranial glioma xenografts in NOD SCID mice, giving a better contrast.