[Normal tissue tolerance to high LET radiotherapy].

Based on the clinical evaluations about over 1800 patients who had been treated with fast neutrons at NIRS, the radiobiological properties of high LET radiations were discussed. The most favorable clinical results by fast neutron treatment had been revealed in such diseases as follows; salivary gland tumors, prostate cancer, Pancoast type lung cancer, osteosarcoma, soft tissue sarcoma. The characteristics of these tumors as to the radiobiological properties and the dose distribution are, 1) relatively slow growing tumors and higher RBE for tumor tissue, and 2) capability of correct delivery of a big radiation doses to the target, without any severe radiation complications. Normal tissue tolerance (NSD formulas) for each tissues were also discussed.