In boron neutron capture therapy (BNCT), boron given as boronophenylalanine (BPA) accumulates transiently not only in tumors but also in normal tissues. Average boron concentrations in transplanted 9L gliosarcoma tumors of 20 rats were 2.5 to 3.7 times concentrations found in blood. Although boron levels in a variety of tissues were also higher than blood the concentrations were less than the lowest found in the tumor. Further note than although BPA is a structural analogue of phenylalanine (Phe), the pathway of BPA uptake into regenerating liver may not be linked to Phe uptake mechanisms
