[Primary lung cancer treated with fast neutron].

Forty-nine patients with primary lung cancer were treated with fast neutron (average energy, 6 MeV) by so-called mixed therapy method at the Institute of Medical Science, University of Tokyo. Control group (Linacx-ray, 10 MV) was not randomized one, however, these patients were treated by the same chief radiotherapist (Dr. Iino) at Shizuoka Prefectural Hospital and its interval was almost the same to neutron group. The crude survival rate did not show any significant difference between them except for 1 year survival of Stage II (p less than 0.05). Radiation pneumonitis and tumor regression were thought to be almost the same. The incidence of pneumothorax (3/49) was somewhat higher than the x-ray group (3/119) but there was no significant difference. We are now planning a new mixed therapy method which has short time interval (less than 3 hours) between neutron and x-ray irradiation in expectation of decrease of shoulder in x-ray surviving fraction curve.