Comparison of MIBG scintigraphy and Computed Tomography 37 Comparison of Meta-Iodo-Benzyl-Guanidine scintigraphy and Computed Tomography for localization of phaeochromocytoma

Objective: To compare the results of CT scanning and MIBG scintigraphy in the localization of phaeochromocytoma. Design: Retrospective study. Setting: University Hospital. Subjects: 24 patients with phaeochromocytoma who presented between 1983 and 1990. Results: In 21 out of 24 patients MIBG scintigraphy provided accurate localization. In 16 out of 18 patients who underwent CT scanning a correct localization was obtained. Conclusion: Sensitivity of the two methods is about equal. In patients with nonfamilial phaeochromocytoma it is advisable to use MIBG scintigraphy as initial localization technique, combined with CT directed by scintigraphic results , if more anatomical information is needed. Graaf JS de, Klooster NJJ, Lange WE de, Piers DA, Zwierstra RP. Nederlands Tijdschrift voor Geneeskunde 1991; 135: 2383-2387. (adapted version) Comparison of MIBG scintigraphy and Computed Tomography 39 INTRODUCTION Since the first successful operation for phaeochromocytoma in 1926 by César Roux, complete surgical extirpation of all catecholamine-producing tumour tissue is still the only curative treatment1. Phaeochromocytoma is diagnosed on biochemical grounds by measurement of urinary catecholamines and catecholamine metabolites and plasma catecholamines. After the diagnosis has been confirmed, localization of the tumour is of utmost importance for adequate resection. Angiography with or without venous sampling is technically difficult and can provoke hypertensive crisis in these patients 3,4. These techniques have therefore been abandoned and replaced by less invasive localization modalities. Ultrasonography is a non-invasive technique but its sensitivity is low in small adrenal lesions. Moreover, ultrasonography has a high inter-observer bias 3,5. At present (1991), Computed Tomography (CT) and 123I meta-iodo-benzyl-guanidine (MIBG) scintigraphy are the methods of choice for localizing phaeochromocytoma 2,8-12. CT can detect 85% to 95% of intra-adrenal lesions larger than 1 centimetre. Sensitivity decreases in smaller lesions or in case of extra-adrenal phaeochromocytoma 3,4. Meta-iodo-benzylguanidine has a high affinity for chromafin granula of the adrenal medulla and sympathetic tissue. Tumours derived from these tissues, like phaeochromocytoma, neuroblastoma and paraganglioma, have a high up-take of this tracer, thereby using the functional characteristics of these tumours for their localization 7. Sensitivity of 131 I MIBG scintigraphy for detecting phaeochromocytoma is reported to be high (87%-91%). At present, 123I is the preferred isotope labeling compared to 131 I because of the lower radiation load with 123I, which enables to use a higher dose. This study compares the advantages and disadvantages of MIBG scintigraphy and Computed Tomography for the localization of phaeochromocytoma. PATIENTS AND METHODS Between 1983 and 1990, MIBG scintigraphy was performed in all 24 patients with biochemically proven phaeochromocytoma at the University Hospital Groningen, The Netherlands. The patient group comprised 13 women and 11 men with a mean age of 43 years (range 18-73). In 8 patients phaeochromocytoma was associated with the multiple endocrine neoplasia (MEN) type 2 syndrome. In all patients the diagnosis phaeochromocytoma was confirmed by detection of elevated levels of urinary catecholamines (metanephrines and normetanephrines) (Figure 1). Two patients had previous surgery for phaeochromocytoma; in both patients a unilateral adrenalectomy had been performed for phaeochromocytoma. The procedure for MIBG scintigraphy and CT is described in detail elsewhere (Chapter 4). All patients underwent MIBG scintigraphy