Radioiodinated meta-iodobenzylguanidine in the diagnosis of childhood neuroblastoma.

In a group of 97 patients aged from 6 months to 12 years, all with suspected or proven neural crest tumours, metaiodobenzylguanidine (MIBG) scintigraphy was performed at the time of diagnosis and, in some instances, after induction chemotherapy. All the patients underwent a tumour biopsy with cytological and histological analysis, in addition to imaging examinations such as X-rays, ultrasound, computed tomography and magnetic resonance, within a short period before or after scintigraphy. In 82 of 97 cases MIBG was effective in detecting the primary tumour, hence the technique's sensitivity was 84%. A significant different of sensitivity between [131I]MIBG and [123I]MIBG was not demonstrated. As regards metastatic locations, MIBG scans revealed one or more bone metastases in 12 cases, bone marrow involvement (assumed to be present when diffuse and symmetric uptake in the spine, pelvis and possibly other skeletal sites were visualized) in 9 cases, and focal liver metastases or hepatomegaly in 4 cases. Probably owing to the restrictive diagnostic criterion adopted or to the early phase of the bone marrow involvement, the last was found by biopsy but missed by MIBG in 25 cases. The overall sensitivity in detecting metastases was low (48%), but it was much higher if only bone metastases were considered (81%). Twenty-nine patients who had positive scans at diagnosis were checked following 1-2 courses of induction chemotherapy (IC). MIBG scans remained positive in 22 primary tumours, while 7 primary masses were no longer detected. Out of 12 cases showing metastases at diagnosis, two cases with liver lesions became normal and in one case some, but not all, of the bone lesions were not detectable; 4 cases remained abnormal, while in 5 cases bone marrow involvement was not confirmed. Three cases were confirmed to be true negatives; in 4 other cases bone marrow involved not showing at diagnosis was revealed and confirmed by biopsy; 3 cases in which bone marrow involvement was not revealed by MIBG at diagnosis, had normal MIBG and biopsy results after IC; finally, 2 false negative bone marrow cases and 5 true negative cases at diagnosis remained unchanged, but were not checked by biopsy. Performing total body MIBG scintigraphy in childhood neuroblastoma at diagnosis is useful: 1) to predict the nature of the masses detected by other imaging techniques, when biopsy has not yet been performed; 2) for more accurate tumour staging, in addition to standard imaging investigations, MDP scintigraphy and bone marrow aspiration biopsy, thanks to its ability to detect metastatic lesions; 3) to anticipate the decrease in sensitivity of the technique in detecting both the primary mass and the metastases following induction chemotherapy.