The role of radiopharmaceuticals MIBG and (V) DMSA in the diagnosis of medullary thyroid carcinoma.

The diagnostic value of 123/131I meta-iodo-benzylguanidine (MIBG) and 99mTc (V) dimercaptosuccinic acid (DMSA) was investigated in 12 patients with proven medullary thyroid carcinoma (MTC). Scintigraphic imaging with DMSA was negative in nine of 12 patients. Scintigraphy with MIBG was positive in only one case. In proven primary or recurrent disease, DMSA sensitivity was 50% and MIBG sensitivity was 25%. Such sensitivities become much lower in subjects with high calcitonin (CT) levels who have had negative surgical explorations: DMSA 17% and MIBG 0%. DMSA detected tumor in 25% of the patients and MIBG in only 8%. The positivity of these scintigraphies appears to be unrelated to carcinoembryonic antigen and CT plasma levels. Such data suggest that scintigraphies with MIBG and DMSA are only modestly useful in the diagnosis of MTC.