Intra-arterial administration of sodium borocaptate (BSH)/lipiodol emulsion delivers B-10 to liver tumors highly selectively for boron neutron capture therapy: experimental studies in the rat liver model

Boron neutron capture therapy (BNCT) is particle radiotherapy with alpha ((4)He) particle and recoiled lithium nucleus ((7)Li) derived from a reaction of boron ((10)B) and thermal neutron. We investigated applying BNCT to malignant liver tumors. The purpose of the present study was to reveal the efficacy for administration of emulsion of a boron compound (sodium borocaptate; BSH) and lipiodol via a hepatic artery using a rat liver tumor model.Rat liver tumors were developed by direct injection of Walker 256 cells into the liver parenchyma. BSH (75 mg/kg)/lipiodol (0.3 mL/kg) emulsion was administered via the hepatic artery. Boron concentrations in the tumors, liver, and blood were measured at 1, 6, and 12 h after administration. Neutron capture radiography (NCR) was taken to confirm the selective accumulation of (10)B in the liver tumors.Boron concentrations in the liver tumors and the tumor/liver (T/L) boron concentration ratio at 1, 6, and 12 h after administration of BSH/lipiodol emulsion (concentration: T/L ratio) were 479.2 ppm: 4.0, 197.3 ppm: 14.9, and 96.5 ppm: 6.6, respectively. Highly selective irradiation was clearly demonstrated by the NCR images.Intra-arterial administration of BSH/lipiodol emulsion is effective method for delivering high concentration of (10)B selectively to the liver tumors.