Diagnostic and therapeutic potential of new radiopharmaceutical agents in medullary thyroid carcinoma.

Recently developed radiopharmaceuticals have been proposed for imaging medullary thyroid carcinoma (MTC) with some having therapeutic potential. This study compares the imaging results obtained with radioiodinated meta-iodo-benzylguanidine (MIBG), 99mTc (V) DMSA, and 131I F(ab')2 anti-carcinoembryonic antigen (anti-CEA) in a group of MTC patients. In 23 patients 131I MIBG imaging showed a high specificity (no false-positive results) but a less satisfactory sensitivity (50%). In 12 patients 99mTc (V) DMSA revealed a better sensitivity (77%) but a lower specificity (three false-positive results). Positive results were obtained in two of three patients studied with 131I F(ab')2 anti-CEA. These data suggest that the highly sensitive 99mTc (V) DMSA should be considered as a first choice procedure followed by the highly specific radioiodinated MIBG to confirm the initial results. Since radioiodinated MIBG imaging may have therapeutic usefulness, 131I MIBG was evaluated in an integrated treatment protocol in four cases of proven MTC. The preliminary results obtained were encouraging.