Results of clinical applications of fast neutrons in Japan

Clinical trials with fast neutrons were carried out to estimate the indications and schedules for high-LET radiation therapy. Local control rate and incidence of moist desquamation of the patients surviving more than 6 months after completion of therapy was 39.8% and 11% respectively. Radioresistant tumors, such as malignant melanoma, soft-tissue sarcoma or osteosarcoma, and locally advanced tumors responded well to fast neutrons, whereas late reactions of the normal tissues were slightly more severe after fast neutron therapy than those after low-LET irradiations. It is suggested that improvement of the dose distributions will be indispensable to make the best use of high-LET radiation therapy. (author)