Boron Neutron Capture Therapy

Neutron capture therapy (NCT) is a type of radiotherapy for treating locally invasive malignant tumors such as primary brain tumors, recurrent cancers of the head and neck region, and cutaneous and extracutaneous melanomas. Conceptually, BNCT is a “magic bullet” approach to treating tumors in a two-step process: first, the patient is injected with a tumor-localizing drug containing the stable isotope boron-10 (10B), which has a high propensity to capture low energy “thermal” neutrons. In the second step, the patient is radiated with epithermal neutrons, and then the nuclide undergoes a nuclear reaction with the localized release of a substantial amount of energy. In principle, this kills the “tagged” cell but does not damage the surrounding “untagged” normal cells.

Pure beams of very low energy neutrons do not directly deposit much energy in tissue via collisions but rather interact via nuclear transmutation reactions. The basic idea is to selectively attach to the cancer cells a nuclide having a large cross section for capturing a thermal neutron. Although there is ongoing work in developing high-current particle accelerators to produce low-energy thermal or epithermal beams for BNCT, at the present time, all clinical work is being done using moderated neutron beams from nuclear reactors.