New trends in the use of radioimmunoconjugates for the therapy of cancer.

Since 1980, there has been intense research in the area of radiolabeled immunoconjugates for the localization and therapy of cancer in both experimental animal models and in humans. This is based on the potential of MoAbs reactive with tumor-associated antigens as specific carriers of radionuclides, toxins, and chemotherapeutic drugs. Even though there has been much progress, a great deal of work and innovation will be required before the use of radiolabeled immunoconjugates becomes an established method for clinical tumor detection and therapy. The greatest problem is the relatively low tumor uptake of radiolabeled MoAbs in humans. This results in relatively high background levels of radioactivity in normal tissues and insufficient radioactivity in the tumor for the detection of small lesions and for therapeutic efficacy. In the future, one can expect the development of new MoAbs with greater specificity for particular tumor types, improvements in radiolabeling procedures, and the use of more effective nuclides than 131I. Biological, physiological, pathological, and dosimetric considerations need to be addressed in detail. With this additional information, it is hoped that the full potential for radiolabeled immunoconjugates will be realized.