High-LET radiation therapy at the National Institute of Radiological Sciences

During the period from November 1975 to December 1980, 679 patients with locally advanced and radioresistant cancers were treated with fast neutrons which were produced by bombarding a thick beryllium target with 30 MeV deuterons. In this clinical trial, emphasis was placed on the evaluation of local control and complications following the treatment. The effectiveness of fast neutron therapy was evaluated for carcinoma of the oesophagus and the larynx, Pancoast's tumor of the lung and osteosarcoma, on the basis of the local tumor control. The survival rate of the patients with osteosarcoma or carconoma of the oesophagus was found to be improved by fast neutron therapy. The cumulative survival rates of the patients who received either fast neutrons of photons are 63.3% or 17.6%, respectively. In the case of osteosarcoma, the therapeutic gain factor was greater when chemotherapy was combined with fast neutrons than when it was combined with photons. This was considered to be due to the better local control of the tumor by fast neutrons at a dose below the tolerance limit above which complications arise. It is concluded that the positive effects of high-LET radiations will be even more enhanced when radiations with appropriate dose distributions become available