Results of a pilot study on neutron therapy with 600 patients

Combined neutron-photon-irradiation was applied to tumors of medium radiosensitivity. Compared with pure 60CO radiation the tumor destroying effect increased considerably. This was proved by comparative histological investigations of autopsy specimens taken from prospectively selected groups of patients suffering from carcinoma of bronchus, stomach or esophagus. Pure neutron irradiation was used for tumors of high radioresistance. Even when these tumors were irradiated with comparatively low doses (600-1800 cGy), complete or almost complete regression was fairly sure to occur. This was proved for 64 patients having mesenchymal sarcomata and 11 patients having parotid tumors or bronchial cylindromata. Postoperative prophylactic neutron irradiation after the local extirpation is sure to prevent recurrences of radioresistant tumors exhibiting a strong tendency towards recurrence. This was demonstrated for 33 patients (irradiated with doses of approximately 1200 cGy) who were observed for 12-24 months. Regarding normal tissues there is an increased late reaction of the vascular connective tissue of the skin, which serves here as a model for the general regenerative tissue (RBE greater than 4). Sufficient tumor irradiation, however, can be achieved without exceeding the tolerance dose (necrosis at approximately 2000 cGy). A substantial increase in late reaction was also found for the spinal cord after neutron irradiation in comparison with photon irradiation (RBE approximately 4.5), radiomyelonecrosis occurring at 1000 cGy and more. Some of the other normal tissues (stomach, liver, bones) do not manifest a substantial increase in medium-term reactions. Hence, neutron therapy will make possible an essential advance in the treatment of tumors.