Hypoxia and Perfusion Labeling During Photodynamic Therapy

The development of tumor hypoxia during illumination for photodynamic therapy (PDT) can negatively affect treatment outcome. Furthermore, the spatial distribution of this hypoxia may impact the balance between tumor cell damage and vascular damage as mechanisms of photodynamic effect. The hypoxia markers EF3 [(2-(2-nitroimidazol-1 [H]-yl)-N -(3,3,3-trifluoropropyl)acetamide)] or EF5 [(2-(2-nitroimidazol-1 [H]-yl)-N -(2,2,3,3,3-pentafluoropropyl)acetamide)] can provide a quantitative description of the intratumor distribution of hypoxia during PDT. In vivo perfusion labeling coupled with immunohistochemical staining for vascular structure can provide accompanying information on the status of tumor blood flow at treatment conclusion. Taken together these data can be used to access the relative spatial distributions of hypoxia and perfusion during PDT.