Response of Spontaneous Mammary Carcinoma of the C3H Mouse to X Irradiation Given Under Conditions of Local Tissue Anoxia2

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Abstract
The responses of 215 spontaneous mammary adenocarcinomas in adult female C3H mice to single doses of 250 kv X irradiation, given under conditions of local tissue anoxia, have been evaluated. All 43 animals in the control group showed progressive tumor growth that caused the death of all mice within 125 days after they were assigned to this group. Of particular interest were 138 animals whose tumors at the time of irradiation had a median volume of 300 mm3 and ranged from 100 to 600 mm3. A logit analysis, made from the number of animals surviving without recurrence after doses of 3300 to 9400 rads, determined the tumor control dose (TCD50) for half the tumors for each 10-day interval from the 40th to 170th day after treatment. The TCD50 values approached 6200 rads asymptotically at 140 to 170 days. Calculations given are on the basis of 6200 rads, as a single radiation dose to anoxic spontaneous mammary carcinomas of 300 mm3 (≈3.75 × 108 viable cells), yielding a survival fraction corresponding to 1 or more cells in half the tumors treated. From these considerations, the D37 (37% survival dose) for a single anoxic mammary cancer cell was estimated as ≥300 rads, assuming N = 2.

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