In conclusion, since IL-13Rα2 is overexpressed in a variety of human primary tumors including astrocytoma and glioma as well as metastatic tumors, we predict that IL-13Rα2 targeted agents such as IL-13PE will not only target primary tumors but also metastatic tumors [37]. This evidence concerns the gene IL13RA2 and astrocytoma (excluding glioblastoma).