The monoclonal anti-CEA F(ab’)2 fragment MAb BW 431/31, labelled with 123I or111 In, was used for immunoscintigraphy (IS) in 9 patients with medullary cancer of the thyroid (CCC). The results of 11 studies lead to the following conclusions: 1) When using radioiodine as a label for MAb in IS, potassium iodide is absolutely necessary to block the thyroid which is of special importance in patients with thyroid cancer; 2) Preinjection of “cold” MAb reduces the relatively high unspecific uptake (especially in bone marrow) of MAb BW 431/31, which is of special importance for the antibody labelled with 111 In; 3) IS with MAb BW 413/31 in patients with CCC and elevated serum CEA is positive only in cases with large secondaries; and 4) In patients with CCC and several manifestations of secondaries, only a single (large) metastasis may be apparent.
