Intraoperative localization of neuroblastoma in children with 123I- or 125I-radiolabeled metaiodobenzylguanidine

Background: This study describes a novel method of intraoperative localization of neuroblastoma with a gamma-detecting probe, to detect in situ tumor binding of radiolabeled 123I- or 125I-metaiodobenzylguanidine (MIBG) and improve the quality of tumor resection. Methods: Fifty-eight children underwent 66 surgical procedures with intraoperative detection of radiolabeled MIBG. All patients with positive MIBG scintiscans at diagnosis were included in the study. A tumor/background ratio exceeding 2:1 at the time of operation was considered positive, indicating a significant uptake of MIBG, compatible with the presence of malignant cells. The surgeons were requested to evaluate the contribution of the method to the surgical procedure. Sensitivity and specificity of the method with either 123I-labeled MIBG or 125I-labeled MIBG, on the basis of correlations between probe findings and pathologic analysis of 288 resected specimens, were determined. Results: Intraoperative detection was helpful in 65% of surgical procedures, allowing a better definition of tumor limits and extension to locoregional nodes or detection of small and nonpalpable tumors in sites with difficult surgical access, especially during operation for relapse. The detection was not contributory in 35% of the procedures (well-localized tumors, thoracic neuroblastoma for technical reasons, highly differentiated tumors as ganglioneuroma, and tumors with mainly necrosis or fibrosis). The sensitivity of 123I and 125I was the same (91% and 92%), but the specificity of 125I (85%) was significantly higher than that of 123I (55%) ( p < 0.005). Conclusions: First, this study demonstrates the feasibility of intraoperative detection, with radiolabeled MIBG, of neuroblastoma in children. We advocate the use of 125I rather than 123I. Second, the method is useful to improve the quality of macroscopic resection in widespread neuroblastoma with nodal involvement, in sites with difficult access, and in operations for relapse. (Surgery 1998;123:51-7.)