Increased survival due to radioactive estradiol in mice with C3HBA or BW 10232 tumors

The influence of progesterone and estradiol labeled with tritium was studied in mice inoculated with transplantable mammary adenocarcinomas C3HBA or BW 10232. Tumor size, tumor growth rate, and host survival were measured. Radioactive [3H]estradiol administration increased survival time and inhibited tumor growth in mice inoculated with these tumor lines. Tumor growth retardation depended on the amount of radioactivity injected and nonradioactive estradiol was without any salutary effect on tumor size or host survival. Neither survival times nor tumor growth rate were altered by radioactive [3H]progesterone. The underlying mechanism(s) is (are) referable to ionizing radiation by the specific carrier estradiol or to an isotope effect of [3H]estradiol.