Neutron capture therapy of cancer

Neutron capture therapy (NCT) is a noninvasive therapeutic modality for treating locally invasive malignant tumors such as primary brain tumors and recurrent head and neck cancer. Briefly summarized, it is a two-step procedure: first, the patient is injected with a tumor-localizing drug containing the non-radioactive isotope boron-10 (10B) that has a high propensity or cross section (σ) to capture slow neutrons. The cross section of the 10B is many times greater than that of the other elements present in tissues such as hydrogen, oxygen, and nitrogen. In the second step, the patient is radiated with epithermal neutrons, the source of which is either a nuclear reactor or, more recently, an accelerator. After losing energy as they penetrate tissue, the neutrons are absorbed by the capture agent, which subsequently emits high-energy charged particles that can selectively kill tumor cells that have taken up sufficient quantities of 10B.