Californium-252 interstitial implants in carcinoma of the tongue

A clinical study using 252Cf sources in brachytherapy of tumors began in the Research Institute of Medical Radiology of the Academy of Medical Sciences of the USSR in 1973. 252Cf afterloading cells were utilized by the method of simple afterloading. Dosimetry and radiation protection of medical personnel were developed. To substantiate optimal therapeutic doses of 252Cf neutrons, a correlation of dose, time, and treatment volume factors with clinical results of 252Cf interstitial implants in carcinoma of the tongue for 47 patients with a minimum follow-up period of 1 year was studied. Forty-nine interstitial implants have been performed. Seventeen patients received 252Cf implants alone (Group I), 17 other patients received 252Cf implants in combination with external radiation (Group II), and 15 patients were treated with interstitial implants for recurrent or residual tumors (Group III). Complete regression of carcinoma of the tongue was obtained in 48 patients (98%). Recurrences occurred in 1 patient (6%) in Group I, 6 patients (35%) in Group II, and 5 patients (33%) in Group III. Thirteen patients (27%) developed radiation necrosis. The therapeutic dose of neutron radiation from 252Cf sources in interstitial radiotherapy of primary tongue carcinomas (Group I) was found to be 7 to 9 Gy. Optimal therapeutic neutron dose in combined interstitial and external radiotherapy of primary tumors (Group II) was 5 to 6 Gy with an external radiation dose of 40 Gy. For recurrent and residual tumors (Group III), favorable results were obtained with tumor doses of 6.5 to 7 Gy.