A comparison of the imaging characteristics and microregional distribution of 4 hypoxia PET tracers

Sean Carlin, Hanwen Zhang, Megan Reese, Nicholas N. Ramos, Qing Chen, Sally Ann Ricketts

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93 Scopus citations

Abstract

We compared the imaging characteristics and hypoxia selectivity of 4 hypoxia PET radiotracers (18F-fluoromisonidazole [ 18F-FMISO], 18Fflortanidazole [18F-HX4], 18F-fluoroazomycin arabinoside [18F-FAZA], and 64Cu-diacetyl-bis(N4-methylsemicarbazone) [64Cu-ATSM]) in a single murine xenograft tumor model condition using small-animal PET imaging and combined ex vivo autoradiography and fluorescence immunohistochemistry. Methods: Nude mice bearing SQ20b xenograft tumors were administered 1 of 4 hypoxia PET tracers and images acquired 80-90 min after injection. Frozen sections from excised tumors were then evaluated for tracer distribution using digital autoradiography and compared with histologic markers of tumor hypoxia (pimonidazole, carbonic anydrase 9 [CA9]) and vascular perfusion (Hoechst 33342). Results: The highest tumor uptake was observed with 64Cu-ATSM (maximum standardized uptake values [SUVmax], 1.26 ± 0.13) and the lowest with 18F-FAZA (SUVmax, 0.41 ± 0.24). 18F-FMISO and 18F-HX4 had similar intermediate tumor uptake (SUVmax, 0.76 ± 0.38 and 0.65 ± 0.19, respectively). Digital autoradiographs of hypoxia tracer distributionwere compared pixel by pixelwith images of immunohistochemistry stains. The fluorinated nitroimidazoles all showed radiotracer uptake increasing with pimonidazole and CA9 staining. 64Cu-ATSM showed the opposite pattern, with highest radiotracer uptake observed in regions with the lowest pimonidazole andCA9staining. Conclusion: The fluorinatednitroimidazoles showed similar tumordistributionswhencomparedwithimmunohistochemistry markers of hypoxia. Variations in tumor standardized uptake value and normal tissue distribution may determine the most appropriate clinical setting for each tracer. 64Cu-ATSM showed the highest tumor accumulation and little renal clearance. However, the lack of correlation between 64Cu-ATSM distribution and immunohistochemistry hypoxia markers casts some doubt on the hypoxia selectivity of 64Cu-ATSM.

Original languageEnglish
Pages (from-to)515-521
Number of pages7
JournalJournal of Nuclear Medicine
Volume55
Issue number3
DOIs
StatePublished - Mar 1 2014

Keywords

  • Animal imaging
  • Autoradiography
  • Hypoxia
  • Immunofluorescence
  • PET

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