Stellenwert der 99mTc-M DP-Skelettszintigraphie beim Neuroblastom

Clinical impact and prognostic value of metaiodobenzylguanidine imaging in children with metastatic neuroblastoma

PURPOSE

The clinical value of metaiodobenzylguanidine (mIBG) scintigraphy in patients with disseminated neuroblastoma (NB) at the time of diagnosis and after induction chemotherapy was evaluated.

PATIENTS AND METHODS

The medical records and imaging studies of 30 patients with stage 4 NB who underwent mIBG scintigraphy and 99mTc hydroxy methylene diphosphonate bone scintigraphy at the time of diagnosis were reviewed. Scores were calculated for the mIBG and bone scintigrams, and outcome according to the initial and follow-up imaging studies was determined.

RESULTS

Discrepancies between bone scintigraphy and mIBG osteomedullary localization were seen in six patients. For the entire cohort, 2-year event-free survival did not significantly differ for the group of patients with initial mIBG or bone scintigraphy scores > or = 10 compared to those with scores < 10 (P = 0.23 and 0.61, respectively). However, for patients older than 1 year, a trend associating worse outcome with mIBG scores > or = 10 at diagnosis was seen (P = 0.08). A trend correlating abnormal mIBG scintigraphy after induction therapy and poor outcome was also observed (P = 0.09). Outcome did not correlate with the results of the bone scintigram studies performed after induction chemotherapy (P = 0.68).

CONCLUSION

Because a discordance between mIBG and bone scintigraphy results were seen in a subset of stage 4 NB patients, both imaging studies should be performed at the time of diagnosis. mIBG imaging studies performed at the time of diagnosis and after induction chemotherapy may be of prognostic value, particularly in stage 4 patients older than 1 year.

Meta-iodobenzylguanidine in children

Meta-iodobenzylguanidine (MIBG) is an effective imaging agent for neuroblastoma and pheochromocytoma in children, MIBG is concentrated by the neurosecretory granules of normal and neoplastic tissues of neural crest origin. The typical normal scintigraphic uptake pattern of MIBG includes the salivary glands, lung, myocardium, liver, gastrointestinal tract, and contents of the urinary bladder. When MIBG is labeled with iodine-123 (123I), the adrenal glands often are seen. The sensitivity and specificity of MIBG imaging is extremely high in both neuroblastoma and pheochromocytoma. MIBG may detect extensive bone and bone marrow involvement in neuroblastoma, in the absence of findings on bone marrow aspiration and biopsy, plain radiographs, and bone scintigraphy. MIBG labeled with 131I has been used with moderate success in the palliation of advanced neuroblastoma and pheochromocytoma. Early therapeutic intervention in advanced neuroblastoma is promising. Current controversies in the application of MIBG include (1)131I versus 123I as a label for imaging studies: Although improved image quality and reduced absorbed radiation dose are achieved with [123I]MIBG imaging, is it actually more efficacious in the detection of neuroblastoma? (2) Use of bone scintigraphy in neuroblastoma: Given the small number of false-negative MIBG scans for bone involvement, can the bone scan be dropped as a routine study in the follow-up of neuroblastoma? (3) Other new imaging agents: Is there a role for labeled monoclonal antibodies, somatostatin analogs, and magnetic resonance imaging of marrow in the routine follow-up of neuroblastoma? (4) Iodine-125 MIBG therapy in neuroblastoma: Is the improved energy deposition of 125I at extremely short range useful in the ablation of micrometastases? (5) Early therapy with MIBG in neuroblastoma: Is there a role for MIBG therapy in the initial therapeutic regimens of children with advanced neuroblastoma? Twelve years after the initial report of its use in humans, MIBG has become an important imaging agent in pediatric neural tumors, one that is used routinely and efficaciously in many centers. In the next few years we will continue to learn more about its use, particularly in the therapy of advanced neural crest tumors.