The Clinical Value of Imaging Germ Cell Tumours with Radiolabelled Antibodies

Abstract Drug-resistant tumour is a major cause of death from germ cell tumours and whilst the tumour is commonly widespread in the body, there is a proportion of patients in whom the tumour is localised to a single surgically accessable site. CT, MRI and ultrasound can frequently locate residual tumour masses but there is often doubt whether these contain malignant elements. When yolk sac or trophoblastic components are present in the tumour it may be possible to locate them by gamma camera imaging after intravenous injection of radiolabelled antibody to HCG or AFP. Sensitivity is sometimes sufficient to locate tumours which are not detectable by conventional imaging methods and this is particularly valuable when serum HCG or AFP values are raised but no tumour site is known. 131 Iodine labelled antibody is given intravenously and planar and SPECT images obtained after 3 and 6 days when radio labelled antibody has cleared from blood and normal tissues but is retained in the tumour. Genetically engineered antibodies appear to have the potential to improve on the performance of the existing technology through reduced immunogenicity because of replacement of mouse antibody components with human counterparts and by producing earlier imaging with high tumour to normal ratios and site specific labelling with 99m Technetium rather than 131 I. Imaging with radiolabelled antibody can assist in the selection of patients for surgical resection of drug-resistant germ cell tumours.