Capillary permeability and boron distribution in ethylnitrosourea-induced rat glioma.

The vasculature and capillary permeability of gliomas induced by ethylnitrosourea in Sprague-Dawley rats were studied with horseradish peroxidase and Evans blue dye. The distribution of the boron-10 compound, Na2(10)B12H11SH, which is now in clinical use for boron neutron capture therapy (BNCT) for brain tumors, was investigated quantitatively using neutron-induced alpha-autoradiography. The vasculature and the degree of capillary permeability varied widely, depending mainly on the size of the glioma, and were often heterogeneous even in the same tumor. The distribution of boron-10 also varied, correlating to capillary permeability. The boron-10 concentration and the tumor:blood concentration ratio in large and medium-sized gliomas were adequate for successful BNCT. This study suggests that the vasculature and capillary permeability of the target brain tumor exert an important influence on the therapeutic efficacy of BNCT.