The requirement, however, is that sufficient amounts of 10B and thermal neutrons are delivered to the site of the tumor. Because BNCT primarily is a biologically, rather than a physically, targeted type of particle radiation therapy, it should be possible to selectively destroy tumor cells infiltrating normal tissue. Clinical interest in BNCT has focused primarily on high grade gliomas, patients with recurrent tumors of the head and neck region who have failed conventional therapy, and a much smaller number of patients with cutaneous or extra-cutaneous melanomas. In theory, α particles can selectively destroy tumor cells and spare adjacent normal cells. Since α particles have very short pathlengths (5–9 μm) their destructive effects are limited to boron-containing cells (Fig. In order to be successful, ~ 20 μg/g of 10B per weight of tumor must be selectively delivered to the tumor cells (~ 10 9 atoms/cell), and enough neutrons must be absorbed by them to sustain a lethal 10B(n, α) 7Li capture reaction. This results in the production of high-linear energy transfer (LET) alpha (α) particles ( 4He) and recoiling lithium-7 ( 7Li) nuclei (Fig. Therefore, at present the best way to further improve the clinical efficacy of BNCT would be to optimize the dosing paradigms and delivery of BPA and BSH, either alone or in combination, with the hope that future research will identify new and better boron delivery agents for clinical use.īoron neutron capture therapy (BNCT) is based on the nuclear capture and fission reactions that occur when the stable isotope boron-10 ( 10B) is irradiated with either low-energy (0.025 eV) thermal neutrons or, for clinical studies, epithermal neutrons (10,000 eV), which become thermalized as they penetrate tissue. Currently, however, none of these have reached the stage where there is enough convincing data to warrant clinical biodistribution studies. These include boron-containing porphyrins, amino acids, polyamines, nucleosides, peptides, monoclonal antibodies, liposomes, nanoparticles of various types, boron cluster compounds and co-polymers. Because of their limitations, great effort has been expended over the past 40 years to develop new boron delivery agents that have more favorable biodistribution and uptake for clinical use. Although they are far from being ideal, their therapeutic efficacy has been demonstrated in patients with high grade gliomas, recurrent tumors of the head and neck region, and a much smaller number with cutaneous and extra-cutaneous melanomas. Two low molecular weight boron-containing drugs currently are being used clinically, boronophenylalanine (BPA) and sodium borocaptate (BSH). This review will focus on tumor-targeting boron delivery agents that are an essential component of this binary system. Boron neutron capture therapy (BNCT) is a binary radiotherapeutic modality based on the nuclear capture and fission reactions that occur when the stable isotope, boron-10, is irradiated with neutrons to produce high energy alpha particles.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |