Experimental Radioimmunotherapy of a Xenografted Human Colonie Tumor (GW-39) Producing Carcinoembryonic Antigen1

Experiments were undertaken to evaluate the antitumor ef fects of 131l-labeled goat antibody immunoglobulin G prepared against carcinoembryonic antigen in hamsters bearing the carcinoembryonic antigen-producing GW-39 human colonie car cinoma. At a single injection of 1 mCi 131Iand higher, a marked growth inhibition of GW-39 tumors, as well as a considerable increase in the survival time of the tumor-bearing hamsters, could be achieved. At a dose of 1 mCi, the radioactive affinitypurified antibody appeared to be superior to radioactive normal goat immunoglobulin G in influencing tumor growth and survival time, but no signficant difference could be seen at the higher dose of 2 mCi given. Radiobiological calculations indicated that the tumors received, at up to 20 days after therapy, 1325 rads for the specific antibody and only 411 rads for the normal immunoglobulin G preparation. These findings encourage the further evaluation of antibodies to tumor markers for isotopie cancer therapy.