Intraoperative search for neuroblastoma by MIBG and radioguided surgery with the gamma detector.

Administration of a tumour-seeking compound labeled with a low-energy isotope and intraoperative screening with the gamma probe (radioguided surgery, RGS) could be useful in reoperations for advanced neuroblastoma when the normal anatomy is altered. A pilot study was performed to test the feasibility of this technique. Five patients underwent six relaparotomies for recurrent stage III or IV neuroblastoma. All had been treated with intensive chemotherapy and/ or metaiodobenzylguanidine (MIBG)-I131 with or without hyperbaric oxygen. Reoperation was performed to achieve near-total (greater than 95%) excision. In all instances, active tumour was seen on the preoperative MIBG scan. Before the operation, a tracer dose of MIBG-I123 was given. At laparotomy, a search was made with the gamma probe for areas of increased activity. The gamma probe correctly identified active neuroblastoma tissue that was seen on the preoperative MIBG scan. There appeared to be a relationship between intensity of radioactivity and degree of maturation on histologic examination. This pilot study shows that RGS with MIBG and intraoperative use of the gamma probe is able to identify recurrent neuroblastoma. Whether this method is able to detect occult tumour and whether RGS will result in better outcome are the subjects of ongoing research.