[Successful immunoscintigraphic tumor detection with technetium 99m marked monoclonal anti-CEA antibodies]

Twenty patients aged 32-76 years (median 56 years) with various primary cancers or tumor recurrences (colorectal n = 14; lung, breast, medullary thyroid carcinoma n = 2, each) were studied with a technetium-99m labeled anti-CEA antibody. Intact monoclonal antibody BW 431/26 (Scintimum CEA-Tc-99m, Behringwerke AG, Marburg) was successfully labeled (Schwarz Method) by an instant 2-vial kit (labeling efficiency greater than 95% (TLC, HPLC), preserved immunoreactivity). The most frequent clinical indications were (1) the detection of tumor recurrences in patients with a steadily increasing serum CEA level (at a mean 2.3 years after complete removal of the primary tumor) but normal findings by conventional imaging modalities, (2) the search for extrahepatic tumor involvement in patients with known liver metastases scheduled for regional chemotherapy. Gamma camera scintigrams (planar and ECT) were performed 6-12 h and 18-26 h postinjection yielding a sensitivity of 95% (positive tumor contrast in 19/20 patients) with a specificity of 90% (positive predictive value 95%). Immunoscintigraphy successfully depicted tumor recurrences in 4/6 patients with elevated serum CEA values where all conventional imaging modalities had failed. The successful labeling of monoclonal antibodies with 99mTc represent an important step in clinical progress for the more practically orientated use of immunoscintigraphy and also opens new diagnostic fields.