Feasibility of Tumor Immunoradiotherapy Using Radioiodinated Antibodies to Tumor-Specific Cell Membrane Antigens with Emphasis on Leukemias and Early Metastases

Abstract

Theoretical calculations and published data suggest that it is possible to deliver a highly therapeutic dose (500 rad) of β-radiation to individual free floating tumor cells solely by means of ¹³¹I- or ¹³³I-radiantibodies attached to tumor-specific antigens on the cell membrane over one half life of either isotope. The number of specific antigenic sites on tumor cells is apparently hundreds of times greater than the number of radioantibodies required to deliver the dose. Such an approach may be especially useful for destroying low numbers of leukemia cells or early metastases, but it might also be used for the therapy of disseminated tumors with adequate purification of and accessibility to antibodies. Other calculations showed that it is possible to deliver 500 rad to the blood as a whole using tumor-specific radioiodinated antibodies while keeping tissue toxicity at easily tolerated levels assuming that nonspecific adsorption to normal tissues can be discounted. The possible therapeutic potential of various methodological approaches was considered in the light of published findings.