Tumour size: The only predictive factor for I-131 MIBG uptake in phaeochromocytoma and paraganglioma

Background: I-131 Meta-iodobenzylguanidine (I-131 MIBG) scintigraphy can de tect chromaffin rumours with a high specificity but its sensitivity remains limited. In this study, the influence of clinical features and tumour path ology on the results of I-131 MIBG of patients with phaeochromocytomas and paragangliomas was examined. Methods: The records of 104 patients operated on for chromaffin tumours who had pre-operative I-131 MIBG were reviewed. Demographic data, clinical fea tures, biochemical results and pathology of tumours were analysed. The size of the tumour was assessed by the three measured diameters of the specimen and its calculated volume. Univariate relationship between tumours' charac teristics and the results of I-131 MIBG were examined. Results: Out of 119 tumours, 104 (87%) were detected by I-131 MIBG. Mean +/ - SD largest diameter and volume of the tumours were 6.0 +/- 2.4 cm (range 0.8-11.5 cm) and 68 +/- 74 cm(3) (range 0.2-421 cm(3)). Results of I-131 MI BG were significantly correlated with both the largest diameter of the tumo ur (P < 0.01) and by its volume (P < 0.001). I-131 MIBG was negative in 35. 5% of rumours < 20 cm(3) and in 2.6% of those < 20 cm(3). No other criteria were correlated with positive I-131 MIBG, including aetiology, pathology o r catecholamine secretion pattern. Conclusions: The result of I-131 MIBG scanning in patients with chromaffin tumours is significantly correlated with the size of the tumour.