Impact of metaiodobenzylguanidine scintigraphy on assessing response of high-risk neuroblastoma to dose-intensive induction chemotherapy.

PURPOSE: The International Neuroblastoma Response Criteria (INRC) recommend, but do not make mandatory, metaiodobenzylguanidine (MIBG) scans. We present the first report on the effect of MIBG scans on the classification of response to dose-intensive induction therapy.

PATIENTS AND METHODS: After dose-intensive induction and before consolidative therapy, 162 Memorial Sloan-Kettering Cancer Center (MSKCC) patients with high-risk neuroblastoma (NB) had MIBG scans (99 with (131)I, 63 with (123)I), computed tomography, (99m)Tc-bone scan, bone marrow (BM) tests, and urine catecholamine measurements. Induction included high-dose cyclophosphamide (140 mg/kg) plus other agents and high-dose cisplatin (200 mg/m(2))/etoposide (600 mg/m(2)).

RESULTS: In 90 patients treated with dose-intensive therapy from diagnosis at MSKCC, the use of MIBG scintigraphy increased the incomplete response numbers from 14 (15.5%) to 20 (22%), giving a complete remission/very good partial remission (CR/VGPR) rate of 78%. In 72 patients treated before referral to MSKCC for intensified therapy, MIBG findings changed the response classification of one patient; the CR/VGPR rate was 43%. MIBG scans showed no BM disease in 15 of 38 patients with histologically evident NB in BM but did show uptake consistent with BM involvement in five patients who had no NB observed in BM tests.

CONCLUSION: With the less effective therapy consequent to the intensification of induction only after initial exposure to standard-dose chemotherapy, MIBG scintigraphy merely confirms the findings of other staging modalities for detection of relatively widespread residual NB. However, when dose-intensive therapy is initiated at diagnosis, the reliable achievement of major disease responses makes extensive BM testing and MIBG scintigraphy prerequisites for accurate determination of disease status.