TUMOR-LOCALIZATION WITH I-131-LABELED HUMAN-IGM MONOCLONAL-ANTIBODY 16.88 IN ADVANCED COLORECTAL-CANCER PATIENTS

Human IgM monoclonal antibody 16.88 recognised an intracellular antigen strongly expressed in colorectal cancer tissue in 51% of our patients. Tumour localisation was carried out with 185 MBq I-131-16.88 (8 mg) in 20 of these patients with advanced disease. In 16 patients (80%) immunoscintigraphy was positive in at least one organ site with disease. Of all sites, 55% could be visualised. In general, lesions <3 cm could not be detected. Sequential immunoscintigrams of liver metastases showed variable patterns. Initial "cold" lesions corresponded to liver metastases with poor blood supply as indicated by Tc-99m-sulphur-colloid and Tc-99m-HMPAO scintigraphy, respectively. The mean (S.D.) biological half-life (whole body clearance of radioactivity) was 37.6 (5.0) h. A second infusion of I-131-16.88 with the addition of high doses of unlabelled 16.88 could be done safely, but did not result in better visualisation of tumour lesions or affect radioactivity clearance from the body.