A new approach in the treatment of stage IV neuroblastoma using a combination of [131I]meta-iodobenzylguanidine (MIBG) and cisplatin

Timing and chemotherapy association for 131-I-MIBG treatment in high-risk neuroblastoma

Prognosis of high-risk neuroblastoma is dismal, despite intensive induction chemotherapy, surgery, high-dose chemotherapy, radiotherapy, and maintenance. Patients who do not achieve a complete metastatic response, with clearance of bone marrow and skeletal NB infiltration, after induction have a significantly lowersurvival rate. Thus, it's necessary to further intensifytreatment during this phase. 131-I-metaiodobenzylguanidine (131-I-MIBG) is a radioactive compound highly effective against neuroblastoma, with32% response rate in relapsed/resistant cases, and only hematological toxicity. 131-I-MIBG wasutilized at different doses in single or multiple administrations, before autologous transplant or combinedwith high-dose chemotherapy. Subsequently, it was added to consolidationin patients with advanced NB after induction, but an independent contribution against neuroblastoma and for myelotoxicity is difficult to determine. Despiteresults of a 2008 paper demonstratedefficacy and mild hematological toxicity of 131-I-MIBG at diagnosis, no center had included it with intensive chemotherapy in first-line treatment protocols. In our institution, at diagnosis, 131-I-MIBG was included in a 5-chemotherapy drug combination and administered on day-10, at doses up to 18.3 mCi/kg. Almost 87% of objective responses were observed 50 days from start with acceptable hematological toxicity. In this paper, we review the literature data regarding 131-I-MIBG treatment for neuroblastoma, and report on doses and combinations used, tumor responses and toxicity. 131-I-MIBG is very effective against neuroblastoma, in particular if given to patients at diagnosis and in combination with chemotherapy, and it should be included in all induction regimens to improve early responses rates and consequently long-term survival.

High-Risk Neuroblastoma: Poor Outcomes Despite Aggressive Multimodal Therapy

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Neuroblastoma (NBL) is a highly malignant embryonal tumor that originates from the primordial neural crest cells. NBL is the most common tumor in infants and the most common extracranial solid tumor in children. The tumor is more commonly diagnosed in children of 1-4 years of age. NBL is characterized by enigmatic clinical behavior that ranges from spontaneous regression to an aggressive clinical course leading to frequent relapses and death. Based on the likelihood of progression and relapse, the International Neuroblastoma Risk Group classification system categorized NBL into very low risk, low risk, intermediate risk, and high risk (HR) groups. HR NBL is defined based on the patient's age (> 18 months), disease metastasis, tumor histology, and MYCN gene amplification. HR NBL is diagnosed in nearly 40% of patients, mainly those > 18 months of age, and is associated with aggressive clinical behavior. Treatment strategies involve the use of intensive chemotherapy (CTR), surgical resection, high dose CTR with hematopoietic stem cell support, radiotherapy, biotherapy, and immunotherapy with Anti-ganglioside 2 monoclonal antibodies. Although HR NBL is now better characterized and aggressive multimodal therapy is applied, the outcomes of treatment are still poor, with overall survival and event-free survival of approximately 40% and 30% at 3-years, respectively. The short and long-term side effects of therapy are tremendous. HR NBL carries a high mortality rate accounting for nearly 15% of pediatric cancer deaths. However, most mortalities are attributed to the high frequency of disease relapse (50%) and disease reactiveness to therapy (20%). Newer treatment strategies are therefore urgently needed. Recent discoveries in the field of biology and molecular genetics of NBL have led to the identification of several targets that can improve the treatment results. In this review, we discuss the different aspects of the epidemiology, biology, clinical presentations, diagnosis, and treatment of HR NBL, in addition to the recent developments in the management of the disease.

MIBG (metaiodobenzylguanidine) theranostics in pediatric and adult malignancies

Metaiodobenzylguanidine, a guanithidine analog, labeled with ¹²³I and ¹³¹I, is used for imaging and therapy of neuroblastomas and various neural crest tumors like paragangliomas, pheochromocytomas, medullary cancer of thyroid and carcinoids since the past three to four decades. In this review article, we shall revisit metaiodobenzylguanidine as a radiopharmaceutical and its various applications in neural crest tumors.

I-131 Metaiodobenzylguanidine Therapy of Pheochromocytoma and Paraganglioma

Pheochromocytomas and paragangliomas are rare tumors arising from chromaffin cells. Available therapeutic modalities consist of chemotherapy, tyrosine kinase inhibitors, and I-131 metaiodobenzylguanidine (MIBG). I-131 MIBG is taken up via specific receptors and localizes into many but not all pheochromocytomas and paragangliomas. Because these tumors are rare, most therapy studies are retrospective presentations of clinical experience. Numerous retrospective studies and a few prospective studies have shown favorable responses in this disease, including symptomatic, biochemical, and objective responses. In this report, we review the experience of using I-131 MIBG therapy for targeting pheochromocytoma and paragangliomas.

Iodine-131 metaiodobenzylguanidine therapy for neuroblastoma: reports so far and future perspective

Neuroblastoma, which derives from neural crest, is the most common extracranial solid cancer in childhood. The tumors express the norepinephrine (NE) transporters on their cell membrane and take in metaiodobenzylguanidine (MIBG) via a NE transporter. Since iodine-131 (I-131) MIBG therapy was firstly reported, many trails of MIBG therapy in patients with neuroblastoma were performed. Though monotherapy with a low dose of I-131 MIBG could achieve high-probability pain reduction, the objective response was poor. In contrast, more than 12 mCi/kg I-131 MIBG administrations with or without hematopoietic cell transplantation (HCT) obtain relatively good responses in patients with refractory or relapsed neuroblastoma. The combination therapy with I-131 MIBG and other modalities such as nonmyeloablative chemotherapy and myeloablative chemotherapy with HCT improved the therapeutic response in patients with refractory or relapsed neuroblastoma. In addition, I-131 MIBG therapy incorporated in the induction therapy was proved to be feasible in patients with newly diagnosed neuroblastoma. To expand more the use of MIBG therapy for neuroblastoma, further studies will be needed especially in the use at an earlier stage from diagnosis, in the use with other radionuclide formations of MIBG, and in combined use with other therapeutic agents.

Nothing but NET: a review of norepinephrine transporter expression and efficacy of 131I-mIBG therapy

Neuroblastoma is unique amongst common pediatric cancers for its expression of the norepinephrine transporter (NET), enabling tumor-selective imaging and therapy with radioactive analogues of norepinephrine. The majority of neuroblastoma tumors are avid for (123)I-metaiodobenzaguanidine (mIBG) on imaging, yet the therapeutic response to (131) I-mIBG is only 30% in clinical trials, and off-target effects cause short- and long-term morbidity. We review the contemporary understanding of the tumor-selective uptake, retention, and efflux of meta-iodobenzylguanidine (mIBG) and strategies currently in development for improving its efficacy. Combination treatment strategies aimed at enhancing NET are likely necessary to reach the full potential of (131)I-mIBG therapy.

Theranostics: evolution of the radiopharmaceutical meta-iodobenzylguanidine in endocrine tumors

Since 1981, meta-iodobenzylguanidine (MIBG), labeled with (131)I and later (123)I, has become a valuable agent in the diagnosis and therapy of a number of endocrine tumors. Initially, the agent located pheochromocytomas and paragangliomas (PGLs), both sporadic and familial, in multiple anatomic sites; surgeons were thereby guided to excisional therapies, which were previously difficult and sometimes impossible. The specificity in diagnosis has remained above 95%, but sensitivity has varied with the nature of the tumor: close to 90% for intra-adrenal pheochromocytomas but 70% or less for PGLs. For patients with neuroblastoma, carcinoid tumors, and medullary thyroid carcinoma, imaging with radiolabeled MIBG portrays important diagnostic evidence, but for these neoplasms, use has been primarily as an adjunct to therapy. Although diagnosis by radiolabeled MIBG has been supplemented and sometimes surpassed by newer scintigraphic agents, searches by this radiopharmaceutical remain indispensable for optimal care of some patients. The radiation imparted by concentrations of (131)I-MIBG in malignant pheochromocytomas, PGLs, carcinoid tumors, and medullary thyroid carcinoma has reduced tumor volumes and lessened excretions of symptom-inflicting hormones, but its value as a therapeutic agent is being fulfilled primarily in attacks on neuroblastomas, which are scourges of children. Much promise has been found in tumor disappearance and prolonged survival of treated patients. The experiences with therapeutic (131)I-MIBG have led to development of new tactics and strategies and to well-founded hopes for elimination of cancers. Radiolabeled MIBG is an exemplar of theranostics and remains a worthy agent for both diagnosis and therapy of endocrine tumors.

Phase I study of vincristine, irinotecan, and ¹³¹I-metaiodobenzylguanidine for patients with relapsed or refractory neuroblastoma: a new approaches to neuroblastoma therapy trial

PURPOSE

(131)I-metaiodobenzylguanidine (MIBG) is a targeted radiopharmaceutical with activity in patients with relapsed or refractory neuroblastoma. Irinotecan is a known radiosensitizer with activity in neuroblastoma. This phase I study aimed to determine the recommended phase 2 dose of MIBG together with fixed doses of vincristine and irinotecan.

EXPERIMENTAL DESIGN

Patients 1 to 30 years old with relapsed or refractory neuroblastoma and MIBG-avid tumors were eligible. All patients had autologous hematopoietic stem cells (PBSC) available and met standard phase I organ function requirements. Irinotecan (20 mg/m(2)/dose IV) was given on days 0 to 4 and 7 to 11, with vincristine (1.5 mg/m(2) IV) on days 0 and 7. MIBG was given on day 1 following a 3 + 3 phase I dose escalation design starting at 8 mCi/kg MIBG. PBSCs were administered at dose level 8 mCi/kg for prolonged myelosuppression and for all patients at 12 mCi/kg or more.

RESULTS

Twenty-four patients evaluable for dose escalation (median age, 6.7 years; range, 1.9-26.8 years) received 1 (n = 17), 2 (n = 5), or 3 (n = 2) cycles of therapy. Myelosuppression and diarrhea were the most common toxicities. Two of 6 patients at the 18 mCi/kg dose level had dose-limiting toxicity (DLT), including one with protocol-defined DLT with prolonged mild aspartate aminotransferase elevation. Eighteen mCi/kg was the recommended phase 2 dose. Six additional patients were treated at 18 mCi/kg, with one additional DLT. Responses (2 complete and 4 partial responses) occurred in 6 of 24 (25%) evaluable patients.

CONCLUSIONS

MIBG is tolerable and active at 18 mCi/kg with standard doses of vincristine and irinotecan.

[Radio iodized metaiodobenzylguanidine (MIBG) in the treatment of neuroblastoma: modalities and indications]

Neuroblastoma is the most common pediatric extracranial solid cancer. Patients with metastatic disease at initial diagnosis who are greater than 18  months of age and patients with MycN amplified locoregional tumors are treated with intensive multimodal therapy. While this intensive approach has been shown to improve outcome, patients with high-risk disease frequently relapse and fewer than 50% of these patients will be long-term survivors necessitating new approaches for therapy. Derived from the sympathetic nervous system, this tumor typically expresses the norepinephrine transporter. This transporter mediates active intracellular uptake of metaiodobenzylguanidine (MIBG) an analogue of norepinephrine in approximately 90% of patients allowing the use of radiolabeled (metaiodobenzylguanidine) MIBG, for targeted radiotherapy. This article will review the clinical experience of using MIBG as targeted radiotherapy in neuroblastoma. The administration guidelines, toxicity, response and survival are discussed. Recent studies have evaluated combinations of (131)I-MIBG with myeloablative regimens such as chemotherapy agents with radiation sensitizing properties, or with biologic agents. Most of them report a response rate of 30-40% with (131)I-MIBG in patients with relapsed or refractory neuroblastoma. Due to this high response rates and low non-hematologic toxicity, (131)I-MIBG seems to be an interesting agent for incorporation into the upfront management of newly diagnosed patients with high-risk neuroblastoma.

Treatment of advanced neuroblastoma in children over 1 year of age: the critical role of ¹³¹I-metaiodobenzylguanidine combined with chemotherapy in a rapid induction regimen

BACKGROUND

The prognosis of patients with advanced neuroblastoma (NB) remains poor. Major and early responses have an important bearing on treatment outcome. Iodine-131-metaiodobenzylguanidine (¹³¹I-MIBG) has the potential to deliver large doses of radiation specifically to NB cells. We evaluated the toxicity of, and response to, a novel induction regimen that included ¹³¹I-MIBG combined with cisplatin, cyclophosphamide, etoposide, vincristine, and doxorubicin.

PROCEDURE

Thirteen children over 1 year of age with advanced NB at diagnosis were investigated extensively. ¹³¹I-MIBG was administered on day 10; this was preceded by chemotherapy in the five patients in group 1 (described in our previous study), and both preceded and followed by chemotherapy in the eight patients in group 2. The final induction regimen (used for group 2) lasted 1 month. Evaluation was performed 40 days after the start of treatment.

RESULTS

In both groups 1 and 2, the extent of hematologic toxicity, which was the only side effect, was similar to that seen with chemotherapy alone. Doses of ¹³¹I-MIBG as high as 16.6 mCi/kg showed no evidence of toxicity, even in patients with extensive bone marrow infiltration. Overall, we recorded two patients with a complete response (CR), six very good partial responses (VGPR), four partial responses (PR), and one mixed response (MR). In group 2, CR/VGPR were observed in patients treated with higher doses of ¹³¹I-MIBG.

CONCLUSIONS

The results of this pilot study show that ¹³¹I-MIBG, in combination with chemotherapy, appears to play an important role in a new and effective induction regimen for advanced NB.

131I-metaiodobenzylguanidine therapy of neuroblastoma and other neuroendocrine tumors

Treatment with (131)I-metaiodobenzylguanidine (MIBG) has been introduced to the management of neuroendocrine tumors (NET) nearly 30 years ago. It provides efficient internal radiotherapy of chromaffin tumors (neuroblastoma, pheochromocytoma, and paraganglioma), but also of carcinoid and other less frequent tumors. Although for various NET types the role of this treatment form decreased by the emergence of peptide receptor radionuclide therapy, (131)I-MIBG still remains the primary radiopharmaceutical for targeting chromaffin tumors with outstanding efficiency. Results in neuroblastoma with overall response rates around 30% in refractory or recurrent diseases have been improved by combinations with chemotherapy, radiosensitizers, and autologous stem cell support. For adult chromaffin tumors, that is, pheochromocytoma and/or paraganglioma, (131)I-MIBG therapy is currently the most efficient nonsurgical therapeutic modality and applies for inoperable, disseminated disease. The antisecretory effect with powerful palliation of symptomatic disease (response rate: 75%-90%) should also be considered when judging treatment benefit. The results in carcinoid tumors are less pronounced, primarily achieving arrest of tumor growth, and most importantly effective functional control. With the presence of peptide receptor radionuclide therapy, (131)I-MIBG remains the alternative radionuclide in this tumor entity, for example, for patients with renal impairment. Another worthwhile mentioning indication-although less prevalent-are metastatic medullary thyroid carcinomas, especially if functioning. These patients are good candidates for this treatment form in the absence of reasonable surgical options and presence of diagnostic MIBG uptake. This article outlines the current status, results, and methodological improvements of (131)I-MIBG therapy.

Radiolabeled metaiodobenzylguanidine for the treatment of neuroblastoma

INTRODUCTION

Neuroblastoma is the most common pediatric extracranial solid cancer. This tumor is characterized by metaiodobenzylguanidine (MIBG) avidity in 90% of cases, prompting the use of radiolabeled MIBG for targeted radiotherapy in these tumors.

METHODS

The available English language literature was reviewed for original research investigating in vitro, in vivo and clinical applications of radiolabeled MIBG for neuroblastoma.

RESULTS

MIBG is actively transported into neuroblastoma cells by the norepinephrine transporter. Preclinical studies demonstrate substantial activity of radiolabeled MIBG in neuroblastoma models, with (131)I-MIBG showing enhanced activity in larger tumors compared to (125)I-MIBG. Clinical studies of (131)I-MIBG in patients with relapsed or refractory neuroblastoma have identified myelosuppression as the main dose-limiting toxicity, necessitating stem cell reinfusion at higher doses. Most studies report a response rate of 30-40% with (131)I-MIBG in this population. More recent studies have focused on the use of (131)I-MIBG in combination with chemotherapy or myeloablative regimens.

CONCLUSIONS

(131)I-MIBG is an active agent for the treatment of patients with neuroblastoma. Future studies will need to define the optimal role of this targeted radiopharmaceutical in the therapy of this disease.

The norepinephrine transporter and pheochromocytoma

Pheochromocytomas are rare neuroendocrine tumors of chromaffin cell origin that synthesize and secrete excess quantities of catecholamines and other vasoactive peptides. Pheochromocytomas also express the norepinephrine transporter (NET), a molecule that is used clinically as a means of incorporating radiolabelled substrates such as 131I-MIBG (iodo-metaiodobenzylguanidine) into pheochromocytoma tumor cells. This allows the diagnostic localization of these tumors and, more recently, 131I-MIBG has been used in trials in the treatment of pheochromocytoma, potentially giving rise to NET as a therapeutic target. However, because of varying levels or activities of the transporter, the ability of 131I-MIBG to be consistently incorporated into tumor cells is limited, and therefore various strategies to increase NET functional activity are being investigated, including the use of traditional chemotherapeutic agents such as cisplatin or doxorubicin. Other aspects of NET discussed in this short review include the regulation of the transporter and how novel protein-protein interactions between NET and structures such as syntaxin 1A may hold the key to innovative ways to increase the therapeutic value of 131I-MIBG.

Targeted radiotherapy with submyeloablative doses of 131I-MIBG is effective for disease palliation in highly refractory neuroblastoma

PURPOSE

Treatment of refractory neuroblastoma remains a significant clinical problem. Targeted radiotherapy with 131I-MIBG has demonstrated antitumor activity in heavily pretreated neuroblastoma patients with recurrent disease. Response rates may be correlated with total radionuclide dose per kilogram body weight delivered, but higher dose levels are associated with protracted grade 4 hematologic toxicity. The optimal method for using single-agent 131I-MIBG for patients with relapsed high-risk neuroblastoma has not been defined. This study was designed to retrospectively determine the clinical response to 131I-MIBG therapy at submyeloablative doses in patients with refractory neuroblastoma and to describe the toxicities.

PATIENTS AND METHODS

A retrospective chart review of 20 patients with neuroblastoma treated with 131I-MIBG at the Children's Hospital of Philadelphia from 1988 to 2000 was performed. Demographic data, 131I-MIBG dose delivered, toxicities, and clinical responses were reviewed.

RESULTS

A median dose of 9.5 mCi/kg of 131I-MIBG was delivered in 32 courses to 20 patients. Three patients were treated in first complete response, and the remaining 17 patients for residual and/or progressive disease. The objective response rate to the first therapy was 31%, and the remaining patients achieved disease stabilization. In addition, 9 of 11 patients with pain at study entry had significant improvement. Disease response was not correlated with 131I-MIBG dose delivered. No unanticipated toxicities were observed.

CONCLUSIONS

Submyeloablative-dose 131I-MIBG is an effective and relatively nontoxic method for neuroblastoma disease palliation. Most patients show subjective improvement in pain and/or performance status. Increased availability and experience with 131I-MIBG therapy would benefit a large number of children with end-stage neuroblastoma and no realistic hope for cure.

Biological investigation of the platinum(II)-[*I]iodohistamine complexes of potential synergistic anti-cancer activity

Cisplatin chemotherapy in combination with external irradiation or with low-dose continuous internal radiotherapy produces significant supra-additive treatment effects towards several tumor cells. The purpose of our research is to develop a new class of platinum-based anticancer drugs containing moieties of synergistic potency such as platinum core and a radiotherapeutic isotope which, delivered directly to the tumorous cells by a specifically designed vectors, should produce a local enhancement of therapeutic dose. Thus, we have synthesized a new platinum-iodohistamine complex and its radioactive analogues labeled with I-125 and I-131. In the present study some biological properties of those compounds have been investigated. The in vitro screening study pointed out that non-radioactive platinum-iodohistamine complex possesses high cytostatic activity against COLO-205 cells, and moderate activity against HL-60 cell line. No cytotoxicity was observed against MOLT-4 and L-1210 cells, as well as against VERO normal cells. The biodistribution of intravenously administered radioactive platinum-[131I]-iodohistamine complex to normal rats revealed the highest accumulation in the liver (c.a. 40%ID). Intraperitoneal injections of the complex to tumor-bearing C3H mice resulted in scattering of the dose in the organs (mainly in GIT, liver, kidney). The retention of radioactive complex in neoplastic tissue was 3-4 times higher than in normal muscular tissue, although exhibited the tendency to decrease with time post injection. The results of the present study show promising features of the newly developed platinum-iodohistamine complexes and justify prospective investigation of in vivo anticancer potency on animal models of solid tumors.

Thyroidal uptake and radiation dose after repetitive I-131-MIBG treatments: influence of potassium iodide for thyroid blocking

BACKGROUND

In I-131-MIBG therapy, I-131-iodide can be released from the I-131-MIBG molecule. Hypothyroidism might result from the undesirable irradiation of the thyroid gland. To prevent this, stable iodide such as potassium iodide (KI) is given to oversaturate the thyroid before I-131-MIBG is administered.

PROCEDURE

In the present study, the incidence of hypothyroidism (elevated TSH) was correlated with the thyroidal uptake of I-131 and dose (MIRD dosimetry) after 35 individual treatments in ten patients. Iodine-131-MIBG therapy was performed using a modified dosage of 1.9-11.1 GBq (50-300 mCi) IV. Premedication with KI was done as recommended with a dose of 100 mg KI orally from 2 days before until 4 weeks after I-131-MIBG.

RESULTS

The absorbed thyroidal dose amounted to a very variable range of 0.2 (patient # 1) up to 30.0 (patient 3) Gy with 7.1 +/- 7.9 Gy per treatment and 24.1+/- 19.2 Gy per patient (mean+/- SD), despite the same and compliantly taken KI premedication protocol. Up to now, 4/10 or 40% of patients have developed hypothyroidism after a mean follow-up period of 11 months and a mean total administered dose of 18.7 GBq (505 mCi). A trend towards higher thyroidal doses was seen in the hypothyroid patients.

CONCLUSIONS

This study observes a general high inter- and intra-individual variability in radio-iodide uptake in the thyroid after I-131-MIBG therapy despite KI premedication, as well as possible occurrence of hypothyroidism. A dose-response relationship needs confirmation on a larger cohort of patients to reach statistical value. An alternative thyroid cytoprotection strategy for possible long-term survivors may be considered.

Synthesis of ring- and side-chain-substituted m-iodobenzylguanidine analogues

With the goal of developing MIBG analogues with improved targeting properties especially for oncologic applications, several radioiodinated ring- and side-chain-substituted MIBG analogues were synthesized. Except for 3-[(131)I]iodo-4-nitrobenzylguanidine and N-hydroxy-3-[(131)I]iodobenzylguanidine, the radioiodinated analogues were prepared at no-carrier-added levels from their respective tin precursors. The radiochemical yields generally were in the range of 70-90% except for 3-amino-5-[(131)I]iodobenzylguanidine for which a radiochemical yield of about 40% was obtained. While the silicon precursor N(1),N(2)-bis(tert-butyloxycarbonyl)-N(1)-(4-nitro-3-trimethylsilylbenzyl)guanidine did not yield 3-[(131)I]iodo-4-nitrobenzylguanidine, its deprotected derivative, N(1)-(4-nitro-3-trimethylsilylbenzyl)guanidine was radioiodinated in a modest yield of 20% providing 3-[(131)I]iodo-4-nitrobenzylguanidine. Exchange radioiodination of 3-iodo-4-nitrobenzylguanidine gave 3-[(131)I]iodo-4-nitrobenzylguanidine in 80% radiochemical yield. No-carrier-added [(131)I]NHIBG was prepared from its silicon precursor N(1)-hydroxy-N(3)-(3-trimethylsilylbenzyl)guanidine in 85% radiochemical yield.

Does simple estimation of 131I-metaiodobenzylguanidine uptake in patients with neural crest tumours correlate with clinical outcome?

A retrospective study was undertaken in six patients (three male and three female) with neural crest tumours who received therapeutic doses of 131I-meta-iodobenzylguanidine (131I-MIBG) (6.7-10.5 GBq). The age range of the patients was 13-65 years (mean 36 years). Quantification of tumour uptake was obtained from images acquired with a large-field-of-view gamma camera on a single occasion between 2 and 10 days post-treatment. Tumour uptake was calculated to be 0.1% and 3.2% of the administered dose, corresponding to uptakes of 6.7-142.8 MBq. Tumour volume was assessed from computed tomography (CT) or magnetic resonance (MR) images and estimates of tumour dose made from the Medical Internal Radiation Dosimetry scheme (MIRD) tables. Estimated doses were between 7 and 113 Gy. Most significantly, our findings indicate that high tumour uptake did not always correlate with good clinical response.

Treatment of advanced neuroblastoma: feasibility and therapeutic potential of a novel approach combining 131-I-MIBG and multiple drug chemotherapy

Biological and clinical observations suggest that initial marked reduction of resistant clones may be critical in any attempt to improve long-term results in advanced neuroblastoma (NB). The aim of this pilot study is to determine short-term toxicity and efficacy of a new therapeutic model based on the simultaneous use of multiple drug chemotherapy and specific irradiation using 131-I-MIBG. The study population consisted of 21 patients, from 1 to 8 years of age with good 131-I-MIBG uptake. 16 extensively pre-treated patients with refractory or relapsed disease were divided into 2 groups. In Group 1 (9 patients) the basic chemotherapy regimen consisted in cisplatin at the dose of 20 mg/m(2) i.v. per day infused over 2 h, for 4 consecutive days; on day 4 Cy 2 g/m(2) i.v. was administered over 2 h followed by Mesna. Group 2 (7 patients) was treated with basic chemotherapeutic regimen plus VP16 and Vincristine. VP16 at the dose of 50 mg/m(2) i.v. per day was administered as a 24 h infusion on days 1-3; Vincristine 1.5 mg/m(2) i.v. was administered on days 1 and 6. On day 10 a single dose of 131-I-MIBG (200 mCi) with a high specific activity (>1.1 GBq/mg) was administered to both Groups by i.v. infusion over 4-6 hours. A further 5 patients were treated at diagnosis: 2 with the same regimen as Group 1 and 3 with the same as Group 2. The severity of toxicity was graded according to World Health Organization (WHO) criteria. Assessment of tumour response was monitored 4-6 weeks after the beginning of combined therapy (CO-TH). Response was defined according to INSS (International Neuroblastoma Staging System) criteria. No extra-medullary toxicity was observed in any patient. Haematological toxicity was the only toxicity observed and seemed mainly related to chemotherapy. Myelosuppression was mild in the 5 patients treated at diagnosis. No serious infections or significant bleeding problems were observed. In the 16 resistant patients, 12 PR, 1 mixed response and 3 SD were obtained. In the 5 patients treated at diagnosis 2 PR, 1 CR and 2 VGPR were observed. No alteration in 131-I-MIBG uptake was observed after the chemotherapy preceding radio-metabolic treatment. The therapeutic results of this pilot regimen of CO-TH resulted in a high percentage of major response after only a single course in both resistant patients and patients treated at diagnosis. Because of the minimal toxicity observed in patients studied at diagnosis so far, there is room for gradual intensification of the treatment. It is to be hoped that this suggested novel approach may represent an important route of investigation to improve final outcome in patients with advanced NB.

Influence of cisplatin and doxorubicin on 125I-meta-iodobenzylguanidine uptake in human neuroblastoma cell lines

The combination of 131I-meta-iodobenzylguanidine (MIBG) with chemotherapy has recently been employed in the treatment of advanced stage neuroblastoma with encouraging results. However, the mechanisms underlying the interaction between these two different modalities of treatment have not yet been explored. In this study, human neuroblastoma cell lines pretreatment with cisplatin and doxorubicin increased cellular 125I-MIBG accumulation in a dose-dependent manner. Cell cycle analysis showed that increased 125I-MIBG accumulation correlated with the drug-induced G2/M phase block. Northern blot analysis demonstrated an increase in gene expression of the noradrenaline transporter induced by doxorubicin, but not by cisplatin treatment. Increased 125I-MIBG accumulation was also observed in murine xenografts of the human neuroblastoma cell line SK-N-DZ or BE(2)M17 treated intraperitoneally (i.p.) with cisplatin or doxorubicin, respectively. These results suggest that the combination of 131I-MIBG and these drugs could selectively increase radiation doses delivered to neuroblastomas.

Role of 131I-metaiodobenzylguanidine in the treatment of neuroblastoma

BACKGROUND

Standard chemo-radiotherapy methods for the treatment of children with advanced neuroblastoma (NBL) including bone marrow transplant approaches have been disappointing. These poor results can be ascribed to the evolution of residual drug-resistant cell populations. Curative attempts should therefore be directed to their elimination during induction treatment. This can best be accomplished through the use of multiple, non-cross-resistant agents early in therapy. 131I-Metaiodobenzylguanidine (131I-MIBG) provides a mechanism for the delivery of high doses of radiation to NBL lesions. Experience reported from several institutions indicates an approximate 50% response rate in previously treated children with advanced NBL.

CONCLUSIONS

A better strategy is to employ 131I-MIBG together with intensive chemotherapy at the time of diagnosis. A pilot study adopting these principles and supported by laboratory data has been designed and is underway.

Toxicity to neuroblastoma cells and spheroids of benzylguanidine conjugated to radionuclides with short-range emissions

Radiolabelled meta-iodobenzylguanidine (MIBG) is selectively taken up by tumours of neuroendocrine origin, where its cellular localization is believed to be cytoplasmic. The radiopharmaceutical [131I]MIBG is now widely used in the treatment of neuroblastoma, but other radioconjugates of benzylguanidine have been little studied. We have investigated the cytotoxic efficacy of beta, alpha and Auger electron-emitting radioconjugates in treating neuroblastoma cells grown in monolayer or spheroid culture. Using a no-carrier-added synthesis route, we produced 123I-, 125I-, 131I- and 211At-labelled benzylguanidines and compared their in vitro toxicity to the neuroblastoma cell line SK-N-BE(2c) grown in monolayer and spheroid culture. The Auger electron-emitting conjugates ([123I]MIBG and [125I]MIBG) and the alpha-emitting conjugate ([211At]MABG) were highly toxic to monolayers and small spheroids, whereas the beta-emitting conjugate [131I]MIBG was relatively ineffective. The Auger emitters were more effective than expected if the cellular localization of MIBG is cytoplasmic. As dosimetrically predicted however, [211At]MABG was found to be extremely potent in terms of both concentration of radioactivity and number of atoms ml(-1) administered. In contrast, the Auger electron emitters were ineffective in the treatment of larger spheroids, while the beta emitter showed greater efficacy. These findings suggest that short-range emitters would be well suited to the treatment of circulating tumour cells or small clumps, whereas beta emitters would be superior in the treatment of subclinical metastases or macroscopic tumours. These experimental results provide support for a clinical strategy of combinations ('cocktails') of radioconjugates in targeted radiotherapy.

The effect of cisplatin pretreatment on the accumulation of MIBG by neuroblastoma cells in vitro

[131I]meta-iodobenzylguanidine ([131I]MIBG) provides a means of selectively delivering radiation to neuroblastoma cells and is a promising addition to the range of agents used to treat neuroblastoma. As MIBG is now being incorporated into multimodal approaches to therapy, important questions arise about the appropriate scheduling and sequencing of the various agents employed. As the ability of neuroblastoma cells to actively accumulate MIBG is crucial to the success of this therapy, the effect of chemotherapeutic agents on this uptake capacity needs to be investigated. We report here our initial findings on the effect of cisplatin pretreatment on the neuroblastoma cell line SK-N-BE (2c). After treating these cells with therapeutically relevant concentrations of cisplatin (2 microM and 20 microM), a stimulation in uptake of [131I]MIBG was observed. Reverse transcription-polymerase chain reaction (RT-PCR) analysis demonstrated that this effect was due to increased expression of the noradrenaline transporter. These results suggest that appropriate scheduling of cisplatin and [131I]MIBG may lead to an increase in tumour uptake of this radiopharmaceutical with consequent increases in radiation dose to the tumour.

Optimal use of the 131-I-metaiodobenzylguanidine and cisplatin combination in advanced neuroblastoma

Neuroblastoma (NB), a childhood radiosensitive tumor, is very aggressive and malignant, in its disseminated form, despite very intensive chemotherapy, prognosis continues to be dismal. Owing to its capacity to concentrate in NB lesions, large doses of 131-I-MIBG, have given very encouraging therapeutic results in patients resistant to conventional therapy as well as at diagnosis. We recently reported the first attempt in combination therapy (CO-TH) using 131-I-MIBG and cisplatin. This new form of CO-TH appears very effective in obtaining a rapid and excellent response in relapsed patients. In this report, we describe the results of further experience with CO-TH in disseminated NB. We have attempted to verify to what extent interaction between the effects of the two agents may produce therapeutic benefit, and we have sought the optimization of CO-TH use. Three stage IV NB patients were treated with CO-TH. The following treatment schedule, was planned: day 1, cisplatin 50 mg/m3 i.v. over 6 h; day 2, 131-I-MIBG 100-130 mCi at high specific activity (-1.1 Gbq/mg) i.v. over 6 h followed, a week later, by the same treatment combination. The therapeutic results were encouraging. However, hematological toxicity continued to represent a major limiting factor. In view of the overall effectiveness of CO-TH, at the price of lasting hematological toxicity, it may be indicated as a consolidation regimen some time before conditioning chemotherapy for autologous bone marrow transplantation.