Three radiolabelled substances, 111In-pentetreotide, 99mTc-(V)DMSA and 123I-MIBG with different kinetics but similar
tumor seeking behavior, were i.v. injected to assess and correlate their clinical value in metastatic malignant
pheochromocytomas (4 patients), stage III and IV
neuroblastomas (7 patients) and medullary
thyroid carcinomas (6 patients). All II
pheochromocytoma/
neuroblastoma patients received i.v. a dose of III MBq (3 mCi) of 123I-MIBG and 185 MBq (5 mCi) of 111In-pentetreotide, within approximately weeks each other. Furthermore, in 4 of these patients as well as in all medullary
thyroid carcinoma patients 111 MBq (3 mCi) of 99mTc-(V)DMSA were applied i.v. I week prior to the
pentetreotide/mlBG scans. Four patients (malignant
pheochromocytoma) with a total of 7 foci showing
MIBG accumulation had 3 sites with
pentetreotide and 1 site with (V)
DMSA uptake, while in 7 patients (neuroblastora) with 15 foci showing
MIBG accumulation 10 sites had detectable
pentetreotide and 3 sites detectable (V)
DMSA. Of the three radiotracers, 111In-pentetreotide used for
somatostatin receptor identification holds promise mainly in cases where foci imaged with 123I-MIBG are negative. 111In-pentetreotide is unlikely to replace 123I-MIBG as a first-line routine diagnostic scintigraphic modality; compared to
pentetreotide or
MIBG, (V)
DMSA seems to be highly sensitive only in medullary
thyroid carcinomas.