Radioimmunodetection of cervical carcinoma xenografts with (111)In-labeled MAb Cx-99 detected by a hand-held gamma detector

PURPOSE: To establish a radioimmunodetection (RAID) system for localization of cervical cancer by labeling 111-indium ((111)In) to a monoclonal antibody against cytokeratin 19 (MAb Cx-99), and detecting it with a hand-held gamma detector in an animal model. METHODS: MAb Cx-99 was labeled with 111-Indium by the DTPA chelating method. From the second day to the seventh day after injection of this immunoconjugate into athymic nude mice bearing cervical cancer cell line CC7T xenografts, the biodistribution ratios of tumor and non-tumor radioactivity were detected by a hand-held gamma detector. Data were also correlated with the data detected by the conventional gamma counter. RESULTS: The labeling efficiency of this (111)In-labeled MAb Cx-99 and (111)In-labeled MOPC was 91.6% and 95.5%, respectively. After injection, the liver, kidney and lung were initially noticed to have high radioactivity, but the localization of tumor/tissue ratios increased progressively as time passed, indicating the effect of delayed detection for distinguishing tumor from non-tumor tissues. Except for the spleen, the range of tumor/tissue ratios was 1.18-32.7 and 1.14-39.35 for the fourth day and the seventh day, respectively. The tumor/spleen ratio remained low until the seventh day after injection, thus indicating that the spleen might have a different excretion rate. CONCLUSION: This study indicated the feasibility of a hand-held detection system in the localization of cervical cancer after injection of (111)In-labeled MAb Cx-99. The effect of delayed detection was obvious by the decreasing high bindings in the liver, spleen and kidney, with the applicable detection time being four to seven days after injection.