New tracers for the imaging of the medullary thyroid carcinoma.

I-MIBG and 99Tcm(V)-DMSA have been recently proposed as scintigraphic markers of the medullary thyroid carcinoma (MTC). Thirty two patients were examined with 131I- or 123I-MIBG and 26 of these were re-examined with 99Tcm(V)-DMSA (planar and SPECT). From our experience we can draw the following conclusions: (1) the scintigraphic attempt was useless in patients with normal levels of plasma calcitonin (CT): (2) in patients with high plasma CT levels, the sensitivity of the MIBG was better in familiar (3/3 true positive) than in sporadic disease (7/21 true positive; overall sensitivity = 42%); the 99Tcm(V)-DMSA was positive in 16/19 cases, (overall sensitivity = 84%) even in cases which had been false negative with MIBG (6 patients); (3) no false positive results were found; (4) the scan with 99Tcm(V)-DMSA is then suggested as the first imaging approach during the follow up in patients affected by MTC and still having high levels of plasma CT. The MIBG scan should be limited to the patients in whom the possible use of MIBG therapy has to be investigated.