Selective tumor localization in experimental hepatoma by radiolabeled antiferritin antibody

The in vivo localization of 131I-radiolabeled antiferritin and normal IgG in the H-4-II-E rat hepatoma model was investigated by serial necropsy. Groups of 14 to 18 animals were injected with 500 microCi (200 micrograms) of normal and antiferritin IgG. The total dose from the nonpenetrating beta radiation was calculated for tumor and normal tissue, and expressed as a targeting ratio of antiferritin to normal IgG for each organ studied. The results demonstrate 2.9 times greater dose deposition in tumors of animals treated with 131I-antiferritin than with 131I-normal IgG. 131I-antiferritin deposited equivalently in primary tumors and metastatic lesions of similar size. The specific binding in tumors could be competitively inhibited by the addition of unlabeled antiferritin but not unlabeled normal IgG. Specific targeting with 131I-antiferritin comparison to 131I-normal IgG did not occur in any normal tissue. There was considerable variation in the dose deposition in different normal tissues.