Prospects for radiolabeled monoclonal antibodies in metastatic disease.

Many monoclonal antibodies are now available that bind to human cancer cells with varying degrees of specificity. These antibodies can be labeled with various radionuclides, permitting tumor sites in the body to be imaged with scintillation cameras. SPECT, the emission counterpart of x-ray computed tomography, provides both qualitative and quantitative information in three dimensions about antibody distribution. We have detected a metastasis as small as 5 mm in a patient, and the theoretical limit of detection size is less than 1 mm. Tumors that are imaged with radiolabeled antibodies can be effectively treated with the same substance (radioimmunotherapy).