Radioimmunoscintigraphic detection of occult gestational choriocarcinoma

Localized recurrent gestational choriocarcinoma, evidenced by a rising level of the β-subunit of human chorionic gonadotropin, can be difficult to localize for surgical resection. We describe a patient with a rising level of the β-subunit of human chorionic gonadotropin after extensive therapy for choriocarcinoma in which gamma scanning of the distribution of an intravenously administered iodine 131-labeled monoclonal antibody preparation (5F9.3) allowed localization of a focus of recurrent choriocarcinoma in the lung. Other imaging methods showed this only as a focus of stable scarring. The antibody scan guided surgical resection of this tumor focus, which on gamma counting had a tenfold excess of antibody activity compared with that of the normal lung. This approach may be useful in detecting occult foci of gestational choriocarcinoma for surgical resection in patients with rising levels of the β-subunit of human chorionic gonadotropin and is under further evaluation.