Relationship of the I-123 Metaiodobenzylguanidine (MIBG) Uptake and Early Relapse of Neuroblastome Using Semi-quantitative Analysis of SPECT/CT

Objectives I-123 metaiodobenzylguanidine (MIBG) scintigraphy is a useful tool for the diagnosis of neuroblastoma. Hybrid single photon emission computed tomography / computed tomography (SPECT/CT) is expected to provide additional anatomical information, and more efficient diagnostic capability. However, there is no report about the prognostic value of I-123 MIBG SPECT/CT of neuroblastoma. The purpose of this study is to evaluate the relationship of I-123 MIBG SPECT/CT uptake and early relapse of neuroblastoma.

Methods Eleven patients (male / female : 5 / 6, age: 0-5 yrs (median 20 mos)) with neuroblastoma from Jan 2010 to Jun 2015 were incorporated in this study. Inclusion criteria were following: 1) I-123 MIBG SPECT/CT was performed before the initiation of treatment, 2) diagnosis of neuroblastoma was proven histopathologically. All patients were clinically followed after the treament. Follow-up term was 7-45 mos (median 25 mos). Clinical stage (International Neuroblastoma Staging System: INSS) of the patients were 6 in stage4, 2 in stage4S, 2 in stage3 and 1 in stage1. N-myc expression was assessed in all patients. For semi-quantitative analysis of I-123 MIBG SPECT/CT, tumor-to-muscle ratio (T/M) was defined as the ratio of mean count of whole tumor divided by that of latissimus dorsi muscle. Region of interests (ROI) was determined by referencing CT image and uptake count was measured with SPECT image.

Results In the follow-up term, 3 patients were diagnosed recurrence after the initial treatment and others revealed no evidence of recurrence. Progression-free survival of recurrence cases were 7, 13 and 25 mos. All recurrence cases were INSS stage4 with high N-myc expression. Average T/M of recurrence cases (n=3) were 2.7 while those of non-recurrence cases (n=8) were 7.7. T/M was significantly different between recurrence cases and non-recurrence cases with using Student's t-test.

Conclusions Semi-quantitative parameter of I-123 MIBG SPECT/CT may be useful to predict the prognosis of neuroblastoma.