Fast Neutron Therapy

Fast neutron therapy is a specialized and very powerful form of external beam radiation therapy, that offers higher relative biologic effectiveness compared with protons or photons. It is often used to treat certain tumors that are radioresistant, meaning they are very difficult to kill using conventional X-ray radiation therapy. There is some evidence that suggests neutron therapy may be superior for controlling slow-growing tumors such as salivary gland tumors, soft tissue sarcomas, and prostate adenocarcinomas.

Fast neutron radiotherapy uses neutrons having typical energies of several tens of megaelectron volts (MeV) that are generated by accelerating either protons or deuterons with cyclotrons or particle accelerators and then delivering them to an appropriate target, most generally beryllium. It is this higher energy transfer that gives rise to the different radiobiologic properties of fast neutrons, which are advantageous in certain clinical situations.

Neutrons have a greater biologic impact on cells than other types of radiation. However, neutrons do not damage all cells to the same extent, and in some cases, are more damaging to cancerous cells than to healthy cells surrounding the cancer. Thus, for the same amount of radiation, a lethal dose can be delivered to the cancer cells, while a sub-lethal dose is delivered to the healthy tissue. Used carefully, this added impact can be an advantage in certain situations.