title: Measurement of PDT-induced hypoxia in Dunning prostate tumors by iodine-123-iodoazomycin arabinoside.
abstract: Photodynamic therapy (PDT) is known to produce vascular damage in solid tumors resulting in secondary ischemia and tumor cell death from hypoxia. The oxygenation status of both non-treated and PDT-treated Dunning R3327-AT prostate tumors growing in Fischer X Copenhagen rats was investigated with the novel hypoxic marker, 123I-iodoazomycin arabinoside (IAZA). Both qualitative and quantitative data from planar scintigraphy of anesthetized tumor-bearing rats showed increased retention of 123I-IAZA in tumors treated with PDT. Tumor perfusion in the same tumors was measured with 99mTc-hexamethylpropyleneamine oxime (HM-PAO). Region of interest analyses revealed an inverse correlation between tumor hypoxia measured by 123I-IAZA and tumor perfusion as measured by 99mTc-HMPAO (coefficient of correlation, r = -0.72). Planar images of 2-mm frozen sections from a large tumor showed 123I-IAZA selectively retained in the region that had been treated with PDT. This and other iodinated azomycin nucleosides, labeled with 123I, show promise for monitoring tumor oxygenation status non-invasively and, in particular, for monitoring the effectiveness of interstitial PDT treatments where perfusion shutdown is a major mechanism of tumor response.
authors.affiliation: Department of Radiation Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada.
authors.forename: R B
authors.initials: RB
authors.lastname: Moore
authors.forename: J D
authors.initials: JD
authors.lastname: Chapman
authors.forename: J R
authors.initials: JR
authors.lastname: Mercer
authors.forename: R H
authors.initials: RH
authors.lastname: Mannan
authors.forename: L I
authors.initials: LI
authors.lastname: Wiebe
authors.forename: A J
authors.initials: AJ
authors.lastname: McEwan
authors.forename: M S
authors.initials: MS
authors.lastname: McPhee
mesh_terms: D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging; D015687:Cell Hypoxia; D007457:Iodine Radioisotopes; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009368:Neoplasm Transplantation; D009593:Nitroimidazoles; D010100:Oxygen / Q000378:metabolism*; D010778:Photochemotherapy; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000378:metabolism*; D011877:Radionuclide Imaging; D051381:Rats; D014407:Tumor Cells, Cultured
chemical_list: D007457:Iodine Radioisotopes; D009593:Nitroimidazoles; C070588:iodoazomycin arabinoside; D010100:Oxygen