Overview of studies on experimental radioimmunotherapy.

Experimental radioimmunotherapy (RIT) has significantly contributed to the development of clinical RIT. In this overview, the current status of experimental RIT is reviewed, including general principles of RIT and determinants of RIT effects. Areas of active research are reviewed, and the usefulness of multicell spheroids is compared to animal models. The radiobiology of RIT is discussed, and studies that have compared the relative efficacy of RIT with external beam radiation therapy are summarized. Approaches for increasing the therapeutic index of RIT are reviewed, including improvements in antibodies, labeling/chelation chemistry, selection of radionuclides, delivery, fractionated therapy, clearance of unbound radiolabeled monoclonal antibodies, protection of normal tissues, radiosensitization of tumors, utilization of colony-stimulating factors and bone marrow transplantation, and the use of novel targets for RIT and topoisomerase I inhibitors. RIT is a promising new therapy for a wide variety of malignancies that can best be optimized by continued research in the field of experimental RIT. Important areas of future research are discussed that may ultimately potentiate the efficacy and decrease the toxicity of RIT and help determine how to optimally combine RIT with other therapeutic modalities.