This study reviews neutron applications in therapy. Applications of neutrons have a long history in nuclear medicine and different therapy centers have started fast neutron treatment since 1976. This treatment is now routinely performed. The clinical results of fast neutron therapy have been shown that fast neutrons have many advantages as compared to other radiations for some cancers and tumors. Inoperable salivary gland tumors, paranasal sinuses, advanced squamous cell carcinomas of the head and neck, advanced prostate cancer, soft tissue sarcomas, melanomas and brain tumors are cases that treatments by fast neutrons were superior over usual low LET radiation. Since these tumors are resistant to low LET radiations. Furthermore, neutron brachytherapy is an effective treatment for cervix, prostate, skin and breast cancers and more suitable than radiotherapy for cervix and prostate cancers using a californium-252 neutron source brachytherapy. The required dose to kill the same number of cancerous cells by neutrons is about one third in comparison with photons. Clinical reports indicate that a full course of treatment with neutrons consists of 12 treatment sessions, three times a week for four weeks, compared to 30-40 treatments, five times a week for six weeks with photons or electrons. The side effects for fast neutron treatment were similar to those of low LET treatment depending on the total dose transferred and the general health of the patients. Most of the more serious side effects are temporary and normal tissue recovery finally occurs. Fast neutron treatment in comparison with photon treatment has fewer local symptoms such as pain or bleeding.

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