N-(2-diethylaminoethyl)-4-[123I]iodobenzamide as a tracer for the detection of malignant melanoma: simple synthesis, improved labelling technique and first clinical results.

In order to evaluate the behaviour of N-(2-diethylaminoethyl)-4-[123I]iodobenzamide in malignant melanotic disease, we synthesized the bromo compound in a simple one-step reaction. Labelling was performed by non-isotopic bromine-iodine-123 exchange in radiochemical yields up to 60%. By means of isocratic high-performance liquid chromatography, the iodinated product could be isolated with high apparent specific activity. First clinical studies in patients with malignant melanoma using N-(2-diethylaminoethyl)-4-[123I]iodobenzamide showed moderate uptake of the tracer in the tumour and the suspected metastases in all patients. Most of the lesions were detectable with technetium-99m-diethylene triamine penta-acetic acid (DTPA) scintigraphy too, but we were able to detect additional, previously unidentified metastases with benzamide scintigraphy. This changed the therapeutic procedure in two of the five cases investigated so far.