Current status of cancer imaging with radiolabeled antibodies

This editorial reviews the development, current status, and future prospects of cancer imaging with radioactive antibodies, termed radioimmunodetection (RAID). There has been a slow and steady development of this field for more than 35 years, with more recent activity and progress resulting from the identification of human tumor-associated antibodies and suitable human tumor xenograft models, the demonstration that circulating antigens do not prevent radioantibody localization in tumor, the development of computer-assisted and biological methods for reducing non-target background radioactivity, and the advent of hybridoma-produced monoclonal antibodies. At the present time, tumor sites in the range of 1.5 to 2.0 cm can be imaged, with the best resolution of 0.4-0.5 cm being reported with new chelates of 99mTc. A number of factors, including character of the radioantibody and its bioavailability, the tumor antigen site and bioavailability, the character of the radiolabel, and the target tumor's size, location and vascularization, contribute to the sensitivity, specificity, accuracy, and resolution of the method. Already at this early stage of development, RAID has been shown to have, in certain tumor types and with particular antibody and imaging systems, an accuracy of tumor site detection of over 90%, with the disclosure of occult lesions. Carefully designed prospective trials are needed to fully assess the role of this new modality in the management of cancer patients, particularly in early detection of primary and recurrent tumors.