Localization of human sarcoma with radiolabeled monoclonal antibody. A preliminary study

The early localization of recurrent or metastatic sarcoma remains a challenging clinical problem. 125I-labeled monoclonal antibody (Mab) 19-24, produced in our laboratories against a human malignant fibrous histiocytoma, has been evaluated for detection of locally recurrent or metastatic disease in selected sarcoma patients. In vitro testing indicated various degrees of positive Mab reactivity with most sarcoma types, and low but significant reactivity with some nonsarcoma tumors and several normal tissues, including liver. The iodine-labeled Mab had an immunoreactivity of 90% and a high binding constant (8.1 X 10(9) M-1). Biodistribution studies of radioisotope in sarcoma patients showed rapid clearance of radiolabeled from the blood and uptake in tumor deposits, liver, and spleen. A differential in radioactivity kinetics between liver and tumor was also found. Serial patient scanning determined optimal imaging time to be between 24 and 48 h after i.v. infusion of the radiolabeled Mab. Analysis of tissues obtained during surgery (including a dual antibody-label study using a nonspecific Mab) showed selective localization of the Mab into the sarcoma deposits. Radiolabeled Mab shows potential as a clinically useful tool for localization of sarcoma deposits.