Tumor Control and Regrowth Probability After a Single Radiation of Experimental Animal Tumors

Summary

Single radiation dose to yield 50% tumor control (TCD50) of various sizes of C3H mouse mammary carcinoma was examined. Tumor cell sensitivity to single radiation by X-ray or neutrons was determined by endpoint dilution, and the number of tumor cells in the tumor was determined by a count of tumor cell nuclei. A mathematical analysis of tumor control probability was made from these results; a formula was proposed which accounted for cell population kinetics or division probability model, cell sensitivity to radiation, and number of tumor cells. Analysis of regrowth probability of tumors irradiated with a single X-ray indicated that tumors recurring after TCD50 might develop rapid regrowth after a long growth lag or a long period of slow growth, but the probability of cell division was reduced.