Introduction to the fourth conference on radioimmunodetection and radioimmunotherapy of cancer

@tln (10). This required imaging after several days and resulted in poor discrimination of tumors in the liver because of the accretion of the radionuclide by normal liver (10). Subsequent developments involved the use of 99mTcas the isotope of choice and smaller targeting molecules, including monovalent frag ments, subfragments (such as single-chain antigen-binding Fvs), and even receptor-binding peptides, such as somatostatin peptides. The smaller molecules not only offer the opportunity of earlier and more rapid tumor targeting and imaging but also a reduced immunogenicity in patients. This conference, and the past four since 1979 (11—14), have recorded these developments and the intriguing opportunities for a more functional diagnosis of malignant lesions, whereby a single study can reveal various sites of spread, including soft-tissue visceral organs, bone, and even bone marrow. Often, a multitude of radiolog ical modalities, based on anatomical and not biological features, are required for similar staging and disclosure of viable tumor. How small can we make such targeting molecules, and how fast and how small can we image tumors in a practical setting? And how can we use this new modality in combination with the traditional anatomical imaging methods, or perhaps with other functional tests, such as positron emission tomography? Unfortunately, the current political debate involving managed care and cost containment appears to be stifling the development of these technologies, particularly at a commercial level, even before such questions can be studied. Yet, the answers are needed in order to justify the further pursuit of these diagnostic approaches. Perhaps the most obvious effect of the development and study of RAID is RAIT, which involves both the selective targeting of cancer and the concomitant delivery of cytotoxic radiation. RAIl' has expe nenced three basic problems: inadequate antibody accretion resulting in low radiation doses to tumor; dose-limiting myelotoxicity; and munne antibody immunogenicity (2, 8, 15). The first problem has been the most challenging because myelotoxicitycan be mitigated or controlled by autologous bone marrow or stem cell grafting, and/or the use of hematopoieticcytokines, whereas the evocation of antimu sine antibodies can be reduced or prevented by replacing rodent antibodies with humanized forms or totally human immunoglobulins. Increasing antibody accretion and targeting higher doses of the ther