Detection of thyroid tumour using a monoclonal 123I anti-human thyroglobulin antibody

A monoclonal antibody to human thyroglobulin was radiolabelled with ¹²³I NaI and shown to be a stable and biologically active reagent in vivo. When injected intravenously into 12 patients with cancer of the thyroid on thyroxine-replacement therapy, 6 of the 12 patients had localization of the labelled antibody in tumour sites. These results were compared to ¹³¹I scans done on the same patients 1 month after stopping thyroxine. The biological half-life of the antibody in the blood was influenced by the levels of circulating thyroglobulin.