Time Distributions of Recurrences of Immunogenic and Nonimmunogenic Tumors Following Local Irradiation

Abstract

Mice (314) received single-dose irradiation of the right leg and thigh as treatment of an 8 mm mammary carcinoma isotransplant and were then observed until death, usually by 1000 days. The time distributions of death due to local recurrence, radiation-induced sarcoma, distant metastasis in the absence of local regrowth, second primary, intercurrent disease and unknown causes were evaluated. The times for the transplant tumor inoculum to grow to an 8 mm tumor and the times of death due to local regrowth, distant metastasis or induced tumor were all approximately log-normally distributed. Of the 128 recurrences, the latest-appearing 3 were at 300, 323 and 436 days; no recurrences were noted during the time period from 436-1000 days. In some cases absolute cure of mice of the tumor in the leg apparently was achieved by radiation alone at the dose levels employed. Radiation-induced sarcomas began to appear after 300 days. The time of appearance of the radiation-induced tumors was inversely related to radiation dose. Similar data for an immunogenic fibrosarcoma show that recurrences appeared earlier and were more closely bunched with respect to time than the recurrences of mammary carcinoma. The time distribution of the development of radiation-induced tumors in non-tumor-bearing animals was also approximately log-normally distributed; the slope of the time distribution curve was the same as that for radiation-induced tumors in mice which were treated for tumor.