ABSTRACT
The high accumulation and selective delivery of 10B into the tumor tissue are the most important requirements to achieve ef™cient boron neutron capture therapy for cancer (BNCT), because the cell-killing effect of BNCT depends on the nuclear reaction of two essentially nontoxic species, boron-10 (10B) and thermal neutrons, whose destructive effect is well documented in boron-loaded tissues (Barth, 2003, 2009; Hawthorne, 1993; Soloway et al., 1998). Two boron compounds, sodium mercaptoundecahydrododecaborate (Na B H SH; BSH)12 11
phenylalanine (l-10BPA) (Snyder et al., 1958), have been clinically utilized for the treatment of patients with malignant brain tumors (Nakagawa and Hatanaka, 1997) and malignant melanoma (Mishima et al., 1989). According to the theoretical estimations as well as clinical data, three important parameters should be considered in the development of boron carriers for fatally damaging tumor cells with BNCT: (1) boron concentrations in the tumor should be in the range of 20-35 μg 10B/g; (2) the tumor/normal tissue ratio should be greater than 3; and (3) the toxicity should be suf-™ciently low (Barth, R. F. et al., 2005). Recently, BNCT has been applied to various cancers, including head and neck cancer (Aihara et al., 2006; Kato et al., 2004), lung cancer, hepatoma (Suzuki et al., 2007), chest wall cancer, and mesothelioma (Ono et al., unpublished). Therefore, the development of new boron carriers is one of the most important issues that should be resolved to extend the application of BNCT to various cancers.
