Endocrine Abstracts

THE SENSITIVITY OF 123I-MIBG IN THE DETECTION OF HISTOLOGICALLY CONFIRMED CATECHOLAMINE-PRODUCING TUMOURS.

M Ismail, R Foley, WM Drake, AB Grossman, PJ Jenkins, SL Chew, GM

Besser, R Reznek, K Britton, JP Monson

Departments of Endocrinology, Nuclear Medicine and Radiology, St

Bartholomew's Hospital (QMUL), London EC1A 7BE

Radionuclide imaging is widely used for the localization of

catecholamine-producing tumors. This is best performed with 123I-meta-iodo-

benzylguanidine (MIBG), a catecholamine (noradrenaline) analogue that utilises the amine precursor uptake mechanism and may thus be

incorporated into vesicles or neurosecretory granules in the cytoplasm. Gamma-camera images are then obtained using a low-energy collimator interfaced with a computer.

We describe a series of 31 consecutive patients presenting to our department

at St. Bartholomew's Hospital between January 1999 and April 2003 with a

diagnosis of a catecholamine-secreting tumour, elevation of urine

catecholamines and subsequent histological confirmation. 123I-MIBG

scanning was performed pre-operatively in all patients. Our series comprised

20 men (65%) and 11 women (35%); 26/31 of these tumors were primary

adrenal (84%), 3 of which were metastatic at the time of diagnosis

(11.5%); and five were extra-adrenal (16%). 123I-MIBG scanning detected 20/26 primary adrenal catecholamine-producing tumours and 3/5 extra-adrenal tumors giving a sensitivity of 77% and 60% respectively. In patients with metastatic adrenalphaeochromocytoma 123I-MIBG avidity was evident in 2 of the 3

cases.

The overall sensitivity of 123I-MIBG scanning was 74% compared with a

reported sensitivity of 80-90% in previously reported smaller series.

There was no relationship between the biochemical severity of the condition

and the presence or absence of 123I-MIBG avidity. Because our inclusion

criteria depended on histological confirmation, the sensitivity data are a reliable estimate of the yield from this localising technique. Despite the

obvious value of 123I-MIBG in confirming the nature of a radiological abnormality our

sensitivity data indicate the importance of additional cross-sectional imaging modalities in localising biochemically proven catecholamine-producing tumours.