Imaging of Bone and Soft Tissue Tumors Using an Antitumor Monoclonal Antibody

Abstract

Imaging of malignancy in patients using radiolabelled antibodies has now been successfully demonstrated in various tumor types. These include colorectal cancer [2, 11, 14], breast cancer [7], malignant melanoma [13], and ovarian cancer [22]. However, although rodent sarcomas were among the first tumors to be localised using specific antitumor antibodies in animals [12, 18], there is little clinical data concerning immunoscintigraphy in bone and soft tissue tumors. In 1981 a monoclonal antibody raised against an osteosarcoma cell line, 791T, was described by Embleton et al. [4]. This monoclonal antibody showed no reaction with fibroblasts, human red blood cells or peripheral mononuclear cells. However, it reacted strongly against the immunizing osteosarcoma cell line and other osteosarcoma cell lines. It was demonstrated that with the addition of iodine as a radiolabel the antibody maintained its activity against osteosarcoma cell lines. In vivo studies using 791T tumors xenografted into immunodeprived mice showed that radiolabelled 791T/36 localised within the tumors, demonstrated both by external gamma scintigraphy and by direct measurement of uptake when a localisation index of between 4 and 5.6 was found compared with radiolabelled normal mouse immunoglobulin (NMI) [17]. This localisation prompted clinical studies using this radiolabelled antibody in patients with bone and soft tissue and a single case was reported showing clear localisation in a patient with osteosarcoma [8].