[Present status of high LET radiation therapy--fast neutron radiotherapy in Japan]

More than 1,900 patients of advanced and inoperable malignant tumor were treated with fast neutron radiotherapy using 30 MeV (d-Be) and 14 MeV (d-Be) beams at NIRS and IMS between 1975 and 1986. Protocols were largely nonrandomized. Some results have been obtained: 1) results with mixed beam studies for advanced squamous cell carcinoma of the uterine cervix have been equivocal compared with the photon controls. 2) some trends of local control have been observed in the trial of esophageal cancer, early cases of adenocarcinoma of the lung and malignant melanoma. 3) significant better results were observed in the pancoast type lung cancer and osteo sarcoma which was treated by the systemic multimodal treatment. It is concluded that neutrons are efficacious for certain specific tumor types owing to some biological effects, however the problem of inferior dose distribution was the weakness of neutron therapy at present.