An Introduction to Boron Neutron Therapy (BNCT): Current Status and Future Outlook

Boron neutron capture therapy (BNCT) is based on the nuclear reaction, such that B-10 irradiated with low-energy thermal neutrons produces alpha particles with high linear energy transfer and lithium-7. Clinically, BNCT is used primarily for treatment of high-grade glioma or brain metastases from melanoma and, more recently, head, neck and liver cancers. Since reactors have long been used to produce high intensity neutron beams, nuclear reactors have also been used to produce BNCT. Accelerators can also be used to generate quasi-thermal neutrons, but none of them are currently used for BNCT. Boron medications with low molecular weight used in clinic include sodium borocaptate (BSH) and a phenylalanine derivative called boronophenyl alanine (BPA). The main challenge in the development of boron tracers is the selective targeting to reach a sufficient concentration of boron (F 20 Ag / g tumor) so that the tumor receives a sufficient dose of radiation and normal tissues receive minimal radiation. Clinical trials of BNCT are being conducted or have been conducted in various countries. Most patients undergoing BNCT were patients with high-grade brain tumors. The patients underwent surgery for complete or partial removal of the tumor and then received BNCT at various time intervals after surgery. BNCT in combination with other treatments such as surgery, chemotherapy and external beam radiotherapy can also be used as an adjuvant therapy for treatment of other tumors. This concomitant use may lead to improvements in patient survival. According to clinical studies, BNCT is a targeted therapy with promising results and acceptable toxicity. Important issues in this treatment include the need for more selective and effective agents for boron delivery carriers, development of methods for estimating semi-quantitative amounts of boron content in the tumor before treatment, clinical progress of BNCT and the need for randomized clinical trials with known therapeutic efficacy. If these issues are addressed enough, BNCT can develop as a treatment method. Further research is needed to determine the role of BNCT in clinical medicine.