Antibody-mediated radiotherapy.

Antibodies that react with antigens on the surface of tumor cells but not normal cells have great potential for cancer detection and therapy. If radiolabeled without loss of immunologic specificity, such antibodies may be able to deliver cytoxic amounts of radiation. Target-cell specificity and a high extraction coefficient are necessary with any radionuclide in order to minimize normal tissue irradiation. Tumor-cell-retention time and the rate of catabolized radionuclide will also influence ultimate applicability. Among the unanswered questions for choosing a radionuclide is the choice of particle emitter. Although classic beta emitters have been used in a number of clinical situations, they have not had a major impact on disease outcome except in diseases of the thyroid. Unfortunately, Auger emitters such as iodine 125 are cytotoxic only when localized within close proximity to the genome. On the other hand, alpha emitters such as astatine 211 eliminate the need for subcellular sequestration but not cell-specific localization.