Neutron beam therapy (NBT) is a form of external beam radiotherapy in which accelerated neutral subatomic particles (neutrons) are targeted to a tumor mass, with the goal of eradicating malignant cells. Unlike standard photon (x-ray) radiotherapy (XRT), which is characterized by low linear energy transfer (LET), NBT involves high-LET. Compared with XRT, the high-LET of NBT is associated with greater cell killing per unit dose and, theoretically, is superior in overcoming radioresistance in slowly proliferating tumors such as prostate adenocarcinoma.