Fast Neutrons and Protons in Cancer Treatment with the Medical Cyclotron at Nirs

Radiation therapy has made marked progress following introduction of high energy xray, gamma ray and electron accelerators . Neverthe l ess, the fact that the doses delivered to the target volume depend on radiation tolerance of the normal tissues still remaims critical problems. At National Institute of Radiological Sciences ( NIRS ), medical cyclotron was installed on 1973 and the clinical trials with 30 MeV dBe neutrons initiated on 1975 . The results of clinical trials with fast neutrons show that the patients suffering from locally advanced cancers and radioresistant cancers achieved local control of the tumor under radiation tolerance of the normal tissues. The Pancoast tumor of the lung and osteosarcoma found to be the typical indication for fast neutron irradiation. Clinical trial s with 70 MeV protons for the patients suffering from superficial cancers started on 1979, because the beams are able to penetrate only 36 mm depth of the normal tissues . The results show that the tumors were controlled without complications of the normal tissues , excluding the patients who had the tumors recurred after radical irradiation. For the patients with malignant me l anoma, salvage surgery was necessary to manage the residual tumors . Based on the experiences of clinical trials with fast neutrons , and protons , project studies using accelerated heavy ions, characterized by Bragg peak and high LET, have been organized at NIRS in 1984 . Clinical trials with heavy ions will start within 10 years.