Metastatic neuroblastoma in children older than one year: prognostic significance of the initial metaiodobenzylguanidine scan and proposal for a scoring system

Current and upcoming radionuclide therapies in the direction of precision oncology: A narrative review

As new molecular tracers are identified to target specific receptors, tissue, and tumor types, opportunities arise for the development of both diagnostic tracers and their therapeutic counterparts, termed "theranostics." While diagnostic tracers utilize positron emitters or gamma-emitting radionuclides, their theranostic counterparts are typically bound to beta and alpha emitters, which can deliver specific and localized radiation to targets with minimal collateral damage to uninvolved surrounding structures. This is an exciting time in molecular imaging and therapy and a step towards personalized and precise medicine in which patients who were either without treatment options or not candidates for other therapies now have expanded options, with tangible data showing improved outcomes. This manuscript explores the current state of theranostics, providing background, treatment specifics, and toxicities, and discusses future potential trends.

Theranostics in Neuroblastoma

Theranostics combines diagnosis and targeted therapy, achieved by the use of the same or similar molecules labeled with different radiopharmaceuticals or identical with different dosages. One of the best examples is the use of metaiodobenzylguanidine (MIBG). In the management of neuroblastoma-the most common extracranial solid tumor in children. MIBG has utility not only for diagnosis, risk-stratification, and response monitoring but also for cancer therapy, particularly in the setting of relapsed/refractory disease. Improved techniques and new emerging radiopharmaceuticals likely will strengthen the role of nuclear medicine in the management of neuroblastoma.

68Ga-DOTATATE PET/CT for Neuroblastoma Staging: Utility for Clinical Use

Metaiodobenzylguanidine (MIBG) imaging has been the standard for neuroblastoma staging for many decades. Novel agents such as ¹⁸F-DOPA and ⁶⁸Ga-DOTATATE are being used nowadays in academic centers. During the coronavirus disease 2019 (COVID-19) pandemic, procurement of ¹²³I-MIBG has proved particularly challenging, necessitating the use of ⁶⁸Ga-DOTATATE PET. ⁶⁸Ga-DOTATATE is Food and Drug Administration-approved for imaging of somatostatin receptor-positive gastroenteropancreatic neuroendocrine tumors. Methods: ⁶⁸Ga-DOTATATE PET/CT imaging was performed for staging of 3 pediatric patients with neuroblastoma at our institution. A review of the literature was also completed. Results: ⁶⁸Ga-DOTATATE PET/CT scans were successfully performed on all patients. All patients showed ⁶⁸Ga-DOTATATE-avid disease. PET scans showed an excellent spatial resolution and demonstrated high accuracy in concordance with current European Association of Nuclear Medicine guidelines. Conclusion: We have presented ⁶⁸Ga-DOTATATE PET/CT imaging for staging of neuroblastoma and believe it can reliably be used as an alternative to ¹²³I-MIBG. It has technical, clinical, and practical advantages making it an attractive option. Further multicenter studies are required before it can be recommended for standard clinical use.

131 I-Meta-iodobenzylguanidine followed by busulfan and melphalan and autologous stem cell rescue in high-risk neuroblastoma

INTRODUCTION

Despite the progress in current treatments, the event-free survival of high-risk neuroblastoma (HR-NB) patients does not exceed 40%-50%, and the prognosis of refractory or relapsed patients is poor, still representing a challenge for pediatric oncologist. Therapeutic Iodine-131 meta-iodobenzylguanidine (Th-¹³¹ I-MIBG) is a recognized safe and potentially effective treatment for NB.

MATERIALS

This retrospective study reports the outcomes of 28 MIBG-avid NB patients with advanced disease either refractory or relapsed, which was undertaken from 1996 to 2014. Th-¹³¹ I-MIBG was administered shortly before (median: 17 days) high-dose chemotherapy with busulfan and melphalan (HD-BuMel) and autologous stem cell rescue (ASCR) at the Gaslini Institute in Genoa, with the aim of analyzing the feasibility, safety, and efficacy of this approach.

RESULTS

Engraftment occurred in all patients after a median of 14 (11-29) and 30 days (13-80) from ASCR for neutrophils and platelets, respectively. No treatment-related deaths were observed. The main high-grade (3-4) toxicity observed was oral and gastrointestinal mucositis in 78.6% and 7.1% of patients, respectively, whereas high-grade hepatic toxicity was observed in 10.7%. Two patients developed veno-occlusive-disease (7.1%), completely responsive to defibrotide. Hypothyroidism was the main late complication that occurred in nine patients (31.1%). After Th-¹³¹ MIBG and HD-BuMel, 19 patients (67.8%) showed an improvement in disease status. Over a median follow-up of 15.9 years, the three-year and five-year overall survival (OS) probabilities were 53% (CI 0.33-0.69) and 41% (CI 0.22-0.59), and the three-year and five-year rates of cumulative risk of progression/relapse were 64% (CI 0.47-0.81) and 73% (CI 0.55-0.88), respectively. MYCN amplification emerged as the only risk factor significantly associated with OS (HR, 3.58;P = 0.041).

CONCLUSION

Th-¹³¹ I-MIBG administered shortly before HD-BuMel is a safe and effective regimen for patients with advanced MIBG-avid NB. These patients should be managed in centers with proven expertise.

Guidelines on nuclear medicine imaging in neuroblastoma

Nuclear medicine has a central role in the diagnosis, staging, response assessment and long-term follow-up of neuroblastoma, the most common solid extracranial tumour in children. These EANM guidelines include updated information on ¹²³I-mIBG, the most common study in nuclear medicine for the evaluation of neuroblastoma, and on PET/CT imaging with ¹⁸F-FDG, ¹⁸F-DOPA and ⁶⁸Ga-DOTA peptides. These PET/CT studies are increasingly employed in clinical practice. Indications, advantages and limitations are presented along with recommendations on study protocols, interpretation of findings and reporting results.

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.

Validation of Postinduction Curie Scores in High-Risk Neuroblastoma: A Children's Oncology Group and SIOPEN Group Report on SIOPEN/HR-NBL1

A semiquantitative ¹²³I-metaiodobenzylguanidine (¹²³I-MIBG) scoring method (the Curie score, or CS) was previously examined in the Children's Oncology Group (COG) high-risk neuroblastoma trial, COG A3973, with a postinduction CS of more than 2 being associated with poor event-free survival (EFS). The validation of the CS in an independent dataset, International Society of Paediatric Oncology European Neuroblastoma/High-Risk Neuroblastoma 1 (SIOPEN/HR-NBL1), is now reported. Methods: A retrospective analysis of ¹²³I-MIBG scans obtained from patients who had been prospectively enrolled in SIOPEN/HR-NBL1 was performed. All patients exhibited ¹²³I-MIBG-avid, International Neuroblastoma Staging System stage 4 neuroblastoma. ¹²³I-MIBG scans were evaluated at 2 time points, diagnosis (n = 345) and postinduction (n = 330), before consolidation myeloablative therapy. Scans of 10 anatomic regions were evaluated, with each region being scored 0-3 on the basis of disease extent and a cumulative CS generated. Cut points for outcome analysis were identified by Youden methodology. CSs from patients enrolled in COG A3973 were used for comparison. Results: The optimal cut point for CS at diagnosis was 12 in SIOPEN/HR-NBL1, with a significant outcome difference by CS noted (5-y EFS, 43.0% ± 5.7% [CS ≤ 12] vs. 21.4% ± 3.6% [CS > 12], P < 0.0001). The optimal CS cut point after induction was 2 in SIOPEN/HR-NBL1, with a postinduction CS of more than 2 being associated with an inferior outcome (5-y EFS, 39.2% ± 4.7% [CS ≤ 2] vs. 16.4% ± 4.2% [CS > 2], P < 0.0001). The postinduction CS maintained independent statistical significance in Cox models when adjusted for the covariates of age and MYCN gene copy number. Conclusion: The prognostic significance of postinduction CSs has now been validated in an independent cohort of patients (SIOPEN/HR-NBL1), with a postinduction CS of more than 2 being associated with an inferior outcome in 2 independent large, cooperative group trials.

Revisions to the International Neuroblastoma Response Criteria: A Consensus Statement From the National Cancer Institute Clinical Trials Planning Meeting

Purpose More than two decades ago, an international working group established the International Neuroblastoma Response Criteria (INRC) to assess treatment response in children with neuroblastoma. However, this system requires modification to incorporate modern imaging techniques and new methods for quantifying bone marrow disease that were not previously widely available. The National Cancer Institute sponsored a clinical trials planning meeting in 2012 to update and refine response criteria for patients with neuroblastoma. Methods Multidisciplinary investigators from 13 countries reviewed data from published trials performed through cooperative groups, consortia, and single institutions. Data from both prospective and retrospective trials were used to refine the INRC. Monthly international conference calls were held from 2011 to 2015, and consensus was reached through review by working group leadership and the National Cancer Institute Clinical Trials Planning Meeting leadership council. Results Overall response in the revised INRC will integrate tumor response in the primary tumor, soft tissue and bone metastases, and bone marrow. Primary and metastatic soft tissue sites will be assessed using Response Evaluation Criteria in Solid Tumors (RECIST) and iodine-123 (123I) -metaiodobenzylguanidine (MIBG) scans or [18F]fluorodeoxyglucose-positron emission tomography scans if the tumor is MIBG nonavid. 123I-MIBG scans, or [18F]fluorodeoxyglucose-positron emission tomography scans for MIBG-nonavid disease, replace technetium-99m diphosphonate bone scintigraphy for osteomedullary metastasis assessment. Bone marrow will be assessed by histology or immunohistochemistry and cytology or immunocytology. Bone marrow with ≤ 5% tumor involvement will be classified as minimal disease. Urinary catecholamine levels will not be included in response assessment. Overall response will be defined as complete response, partial response, minor response, stable disease, or progressive disease. Conclusion These revised criteria will provide a uniform assessment of disease response, improve the interpretability of clinical trial results, and facilitate collaborative trial designs.

Iodine-131-meta-iodobenzylguanidine therapy for patients with newly diagnosed high-risk neuroblastoma

BACKGROUND

Patients with newly diagnosed high-risk (HR) neuroblastoma (NBL) still have a poor outcome, despite multi-modality intensive therapy. This poor outcome necessitates the search for new therapies, such as treatment with 131I-meta-iodobenzylguanidine (131I-MIBG).

OBJECTIVES

To assess the efficacy and adverse effects of 131I-MIBG therapy in patients with newly diagnosed HR NBL.

SEARCH METHODS

We searched the following electronic databases: the Cochrane Central Register of Controlled Trials (CENTRAL; the Cochrane Library 2016, Issue 3), MEDLINE (PubMed) (1945 to 25 April 2016) and Embase (Ovid) (1980 to 25 April 2016). In addition, we handsearched reference lists of relevant articles and reviews. We also assessed the conference proceedings of the International Society for Paediatric Oncology, Advances in Neuroblastoma Research and the American Society of Clinical Oncology; all from 2010 up to and including 2015. We scanned the International Standard Randomized Controlled Trial Number (ISRCTN) Register (www.isrctn.com) and the National Institutes of Health Register for ongoing trials (www.clinicaltrials.gov) on 13 April 2016.

SELECTION CRITERIA

Randomised controlled trials (RCTs), controlled clinical trials (CCTs), non-randomised single-arm trials with historical controls and cohort studies examining the efficacy of 131I-MIBG therapy in 10 or more patients with newly diagnosed HR NBL.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed the study selection, risk of bias assessment and data extraction.

MAIN RESULTS

We identified two eligible cohort studies including 60 children with newly diagnosed HR NBL. All studies had methodological limitations, with regard to both internal (risk of bias) and external validity. As the studies were not comparable with regard to prognostic factors and treatment (and often used different outcome definitions), pooling of results was not possible. In one study, the objective response rate (ORR) was 73% after surgery; the median overall survival was 15 months (95% confidence interval (CI) 7 to 23); five-year overall survival was 14.6%; median event-free survival was 10 months (95% CI 7 to 13); and five-year event-free survival was 12.2%. In the other study, the ORR was 56% after myeloablative therapy and autologous stem cell transplantation; 10-year overall survival was 6.25%; and event-free survival was not reported. With regard to short-term adverse effects, one study showed a prevalence of 2% (95% CI 0% to 13%; best-case scenario) for death due to myelosuppression. After the first cycle of 131I-MIBG therapy in one study, platelet toxicity occurred in 38% (95% CI 18% to 61%), neutrophil toxicity in 50% (95% CI 28% to 72%) and haemoglobin toxicity in 69% (95% CI 44% to 86%); after the second cycle this was 60% (95% CI 36% to 80%) for platelets and neutrophils and 53% (95% CI 30% to 75%) for haemoglobin. In one study, the prevalence of hepatic toxicity during or within four weeks after last the MIBG treatment was 0% (95% CI 0% to 9%; best-case scenario). Neither study reported cardiovascular toxicity and sialoadenitis. One study assessed long-term adverse events in some of the children: there was elevated plasma thyroid-stimulating hormone in 45% (95% CI 27% to 65%) of children; in all children, free T4 was within the age-related normal range (0%, 95% CI 0% to 15%). There were no secondary malignancies observed (0%, 95% CI 0% to 9%), but only five children survived more than four years.

AUTHORS' CONCLUSIONS

We identified no RCTs or CCTs comparing the effectiveness of treatment including 131I-MIBG therapy versus treatment not including 131I-MIBG therapy in patients with newly diagnosed HR NBL. We found two small observational studies including chilren. They had high risk of bias, and not all relevant outcome results were available. Based on the currently available evidence, we cannot make recommendations for the use of 131I-MIBG therapy in patients with newly diagnosed HR NBL in clinical practice. More high-quality research is needed.

Superiority of SPECT/CT over planar 123I-mIBG images in neuroblastoma patients with impact on Curie and SIOPEN score values

OBJECTIVE

The existing most common semi-quantitative systems used for neuroblastoma diagnosis include Curie and SIOPEN scores, which are based on 123I-MIBG planar scans. The purpose of our study was to find out whether a statistically significant difference exists in evaluation based on planar and SPECT/CT scans. We also compared the Curie and SIOPEN methods in terms of their use in regular practice. Patients; method: 45 patients aged 0-10 years; 213 assessments were done in total, and the Curie and SIOPEN scores were determined in each case based on planar and SPECT/CT scans. Student's T-test and the Bland-Altman plot were used for the statistical analysis.

RESULTS

Both methods demonstrated a statistically significant difference (p < 0.0001) between planar and SPECT/CT evaluation. In the group of 35 patients with neuroblastoma in clinical stages 3 and 4, in 54% of the patients SPECT/CT detected a lesion that was not visible in the planar scan. In 89% of cases, the lesion was confirmed by another imaging method (CT, MRI). In the group of 10 patients in the clinical stage 1, a difference between planar and SPECT/CT scanning was found only in one patient (10%). In the whole set, 25% patients showed a pathological finding only in soft tissues.

CONCLUSION

We recommend to perform semiquantitative evaluation of neuroblastoma based on SPECT/CT scans, particularly in patients in clinical stages 3 and 4. It is advisable to include soft tissues in the score assessment, as well, given that only soft tissues may be involved in up to 25.

123I-MIBG scintigraphy and 18F-FDG-PET imaging for diagnosing neuroblastoma

BACKGROUND

Neuroblastoma is an embryonic tumour of childhood that originates in the neural crest. It is the second most common extracranial malignant solid tumour of childhood.Neuroblastoma cells have the unique capacity to accumulate Iodine-123-metaiodobenzylguanidine (¹²³I-MIBG), which can be used for imaging the tumour. Moreover, ¹²³I-MIBG scintigraphy is not only important for the diagnosis of neuroblastoma, but also for staging and localization of skeletal lesions. If these are present, MIBG follow-up scans are used to assess the patient's response to therapy. However, the sensitivity and specificity of ¹²³I-MIBG scintigraphy to detect neuroblastoma varies according to the literature.Prognosis, treatment and response to therapy of patients with neuroblastoma are currently based on extension scoring of ¹²³I-MIBG scans. Due to its clinical use and importance, it is necessary to determine the exact diagnostic accuracy of ¹²³I-MIBG scintigraphy. In case the tumour is not MIBG avid, fluorine-18-fluorodeoxy-glucose ((18)F-FDG) positron emission tomography (PET) is often used and the diagnostic accuracy of this test should also be assessed.

OBJECTIVES

PRIMARY OBJECTIVES

1.1 To determine the diagnostic accuracy of ¹²³I-MIBG (single photon emission computed tomography (SPECT), with or without computed tomography (CT)) scintigraphy for detecting a neuroblastoma and its metastases at first diagnosis or at recurrence in children from 0 to 18 years old.1.2 To determine the diagnostic accuracy of negative ¹²³I-MIBG scintigraphy in combination with (18)F-FDG-PET(-CT) imaging for detecting a neuroblastoma and its metastases at first diagnosis or at recurrence in children from 0 to 18 years old, i.e. an add-on test.

SECONDARY OBJECTIVES

2.1 To determine the diagnostic accuracy of (18)F-FDG-PET(-CT) imaging for detecting a neuroblastoma and its metastases at first diagnosis or at recurrence in children from 0 to 18 years old.2.2 To compare the diagnostic accuracy of ¹²³I-MIBG (SPECT-CT) and (18)F-FDG-PET(-CT) imaging for detecting a neuroblastoma and its metastases at first diagnosis or at recurrence in children from 0 to 18 years old. This was performed within and between included studies. ¹²³I-MIBG (SPECT-CT) scintigraphy was the comparator test in this case.

SEARCH METHODS

We searched the databases of MEDLINE/PubMed (1945 to 11 September 2012) and EMBASE/Ovid (1980 to 11 September 2012) for potentially relevant articles. Also we checked the reference lists of relevant articles and review articles, scanned conference proceedings and searched for unpublished studies by contacting researchers involved in this area.

SELECTION CRITERIA

We included studies of a cross-sectional design or cases series of proven neuroblastoma, either retrospective or prospective, if they compared the results of ¹²³I-MIBG (SPECT-CT) scintigraphy or (18)F-FDG-PET(-CT) imaging, or both, with the reference standards or with each other. Studies had to be primary diagnostic and report on children aged between 0 to 18 years old with a neuroblastoma of any stage at first diagnosis or at recurrence.

DATA COLLECTION AND ANALYSIS

One review author performed the initial screening of identified references. Two review authors independently performed the study selection, extracted data and assessed the methodological quality.We used data from two-by-two tables, describing at least the number of patients with a true positive test and the number of patients with a false negative test, to calculate the sensitivity, and if possible, the specificity for each included study.If possible, we generated forest plots showing estimates of sensitivity and specificity together with 95% confidence intervals.

MAIN RESULTS

Eleven studies met the inclusion criteria. Ten studies reported data on patient level: the scan was positive or negative. One study reported on all single lesions (lesion level). The sensitivity of ¹²³I-MIBG (SPECT-CT) scintigraphy (objective 1.1), determined in 608 of 621 eligible patients included in the 11 studies, varied from 67% to 100%. One study, that reported on a lesion level, provided data to calculate the specificity: 68% in 115 lesions in 22 patients. The sensitivity of ¹²³I-MIBG scintigraphy for detecting metastases separately from the primary tumour in patients with all neuroblastoma stages ranged from 79% to 100% in three studies and the specificity ranged from 33% to 89% for two of these studies.One study reported on the diagnostic accuracy of (18)F-FDG-PET(-CT) imaging (add-on test) in patients with negative ¹²³I-MIBG scintigraphy (objective 1.2). Two of the 24 eligible patients with proven neuroblastoma had a negative ¹²³I-MIBG scan and a positive (18)F-FDG-PET(-CT) scan.The sensitivity of (18)F-FDG-PET(-CT) imaging as a single diagnostic test (objective 2.1) and compared to ¹²³I-MIBG (SPECT-CT) (objective 2.2) was only reported in one study. The sensitivity of (18)F-FDG-PET(-CT) imaging was 100% versus 92% of ¹²³I-MIBG (SPECT-CT) scintigraphy. We could not calculate the specificity for both modalities.

AUTHORS' CONCLUSIONS

The reported sensitivities of ¹²³-I MIBG scintigraphy for the detection of neuroblastoma and its metastases ranged from 67 to 100% in patients with histologically proven neuroblastoma.Only one study in this review reported on false positive findings. It is important to keep in mind that false positive findings can occur. For example, physiological uptake should be ruled out, by using SPECT-CT scans, although more research is needed before definitive conclusions can be made.As described both in the literature and in this review, in about 10% of the patients with histologically proven neuroblastoma the tumour does not accumulate ¹²³I-MIBG (false negative results). For these patients, it is advisable to perform an additional test for staging and assess response to therapy. Additional tests might for example be (18)F-FDG-PET(-CT), but to be certain of its clinical value, more evidence is needed.The diagnostic accuracy of (18)F-FDG-PET(-CT) imaging in case of a negative ¹²³I-MIBG scintigraphy could not be calculated, because only very limited data were available. Also the detection of the diagnostic accuracy of index test (18)F-FDG-PET(-CT) imaging for detecting a neuroblastoma tumour and its metastases, and to compare this to comparator test ¹²³I-MIBG (SPECT-CT) scintigraphy, could not be calculated because of the limited available data at time of this search.At the start of this project, we did not expect to find only very limited data on specificity. We now consider it would have been more appropriate to use the term "the sensitivity to assess the presence of neuroblastoma" instead of "diagnostic accuracy" for the objectives.

The potential role of pretransplant MIBG diagnostic scintigraphy in targeted administration of 131I-MIBG accompanied by ASCT for high-risk and relapsed neuroblastoma: a pilot study

MIBG is an effective component in treatment of neuroblastoma. Furthermore, MIBG scintigraphy is an imaging modality in primary assessments. None of the previous studies have evaluated the role of pretransplant MIBG scintigraphy in decision making for neuroblastoma treatment. We selected therapeutic regimen based on pretransplant (131) I-MIBG scintigraphy. Twenty high-risk patients were enrolled. On day -30, patients underwent diagnostic MIBG scintigraphy. Patients were then subdivided into two groups (10 cases in each arm). MIBG-avid subgroup received MIBG (12 mCi/kg), etoposide (1200 mg/m2), carboplatin (1500 mg/m2), and melphalan (210 mg/m2). Non-MIBG-avid subgroup received etoposide (600 mg/m2), carboplatin (1200 mg/m2), and melphalan (150 mg/m2). Patients received CRA after ASCT. Mean age at diagnosis was 42.5 months (range, 17-65) in MIBG-avid and 38.9 months (range, 18-65) in non-MIBG-avid patients. Mean age at diagnosis and transplantation did not reveal significant difference between two subgroups. In MIBG-avid patients, the three-yr OS was 66 ± 21%. In MIBG-non-avid subgroup, the three-yr OS was 53 ± 20%. In MIBG-avid and non-MIBG-avid subgroups, the three-yr EFS were 66 ± 21% and 47 ± 19%, respectively. These findings may suggest an effective role in selecting the therapeutic strategy for pre-ASCT MIBG scintigraphy in high-risk neuroblastoma. MIBG-avid subset may benefit from the combination of therapeutic MIBG and high dose of chemotherapy.

Children's Oncology Group's 2013 blueprint for research: neuroblastoma

Estimated 5-year survival rates for patients with non-high-risk and high-risk neuroblastoma are 90% and 50%, respectively. Recent clinical trials have shown excellent outcomes with reduced therapy for non-high-risk disease. For patients with high-risk neuroblastoma treated with chemoradiotherapy, surgery, and stem cell transplantation, the addition of anti-disialoganglioside (GD2) immunotherapy plus cytokines improves survival. Upcoming trials will study the incorporation of targeted radionuclide therapy prior to myeloablative chemotherapy into high-risk treatment. Phase 2 trials will investigate druggable target(s) including mTOR inhibition and GD2-directed therapy in combination with chemotherapy for patients with recurrent neuroblastoma, and ALK inhibition for those with ALK-aberrant tumors.

Iodine-123 Metaiodobenzylguanidine Scintigraphy Scoring Allows Prediction of Outcome in Patients With Stage 4 Neuroblastoma: Results of the Cologne Interscore Comparison Study

Purpose

Radioiodinated metaiodobenzylguanidine (123I-mIBG) scintigraphy is an established imaging method in neuroblastoma. Semiquantitative scoring systems have been developed to assess the extent of disease and response to chemotherapy. We present the results of the comparison between the SIOPEN [International Society of Pediatric Oncology Europe Neuroblastoma Group] score and the modified Curie score.

Patients and Methods

We retrospectively analyzed 147 mIBG scans of 58 patients older than 1 year of age with stage 4 neuroblastoma from German Neuroblastoma Trial NB97 that were assessed according to the SIOPEN and the Curie scoring method. mIBG examinations were performed at diagnosis and after four and six cycles of chemotherapy.

Results

Scoring results were highly correlated between both methods, and interobserver reliability was excellent. A Curie score ≤ 2 and a SIOPEN score ≤ 4 (best cutoff) at diagnosis were correlated to significantly better event-free and overall survival compared with higher scores. After four cycles of chemotherapy, overall survival was significantly better for mIBG-negative patients compared with those with any residual mIBG-positive metastases. After six cycles of chemotherapy, there was no difference in survival between mIBG-negative patients and patients with residual mIBG-positive metastases. Patients without mIBG-positive metastases after four and six cycles of chemotherapy had a better overall survival, but late clearance of mIBG-positive metastases did not improve outcome.

Conclusion

Higher mIBG scores at diagnosis and occurrence of any residual mIBG-positive metastases after four cycles of chemotherapy predicted unfavorable outcome for patients with stage 4 neuroblastoma. Later clearance of metastases did not improve prognosis. The Curie and the SIOPEN score were equally reliable and predictive.

Semiquantitative mIBG scoring as a prognostic indicator in patients with stage 4 neuroblastoma: a report from the Children's oncology group

Radiolabeled metaiodobenzylguanidine (mIBG) is a highly sensitive and specific marker for detecting neuroblastoma. A semiquantitative mIBG score (Curie score [CS]) was assessed for utility as a prognostic indicator for a cohort of patients with high-risk metastatic disease.

METHODS

mIBG scans from 280 patients with mIBG-avid, stage 4 neuroblastoma enrolled on the Children's Oncology Group (COG) protocol A3973 were evaluated at diagnosis (n = 280), after induction chemotherapy (n = 237), and after an autologous stem cell transplantation (n = 178). Individual mIBG scans were evaluated at 10 different anatomic regions, with the scoring of each site (0-3) based on the extent of disease at that anatomic region.

RESULTS

There was no correlation between CS at diagnosis and subsequent treatment outcome. Patients with a CS > 2 after induction therapy had a significantly worse event-free survival (EFS) than those with scores ≤ 2 (3-y EFS: 15.4% ± 5.3% vs. 44.9% ± 3.9%, respectively; P < 0.001). A postinduction CS > 2 identified a cohort of patients at greater risk for an event, independent of other known neuroblastoma factors, including age, MYCN status, ploidy, mitosis-karyorrhexis index, and histologic grade. For MYCN-amplified tumors, the presence (CS > 0) versus absence (CS = 0) of residual mIBG avidity after induction was associated with a significantly worse outcome (3-y EFS: 11.8% ± 7.8% vs. 49.6% ± 7.7%, respectively; P = 0.003). After transplantation, patients with a CS > 0 had an EFS inferior to that of patients with a CS of 0 (3-y EFS: 28.9% ± 6.8% vs. 49.3% ± 4.9%, respectively [n = 133]; P = 0.009).

CONCLUSION

Curie scoring carries prognostic significance in the management of patients with high-risk neuroblastoma. In particular, patients with CSs > 2 after induction have extremely poor outcomes and should be considered for alternative therapeutic strategies.

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.

Neuroblastoma: the impact of biology and cooperation leading to personalized treatments

Neuroblastoma is the most common extra-cranial solid tumor in children. It is a heterogeneous disease, consisting of neural crest-derived tumors with remarkably different clinical behaviors. It can present in a wide variety of ways, including lesions which have the potential to spontaneously regress, or as an extremely aggressive form of metastatic cancer which is resistant to all forms of modern therapy. They can arise anywhere along the sympathetic nervous system. The median age of presentation is approximately 18 months of age. Urinary catecholamines (HVA and VMA) are extremely sensitive and specific tumor markers and are used in diagnosis, treatment response assessment and post-treatment surveillance. The largest national treatment groups from North America, Europe and Japan have formed the International Neuroblastoma Risk Group Task Force (INRG) to identify prognostic factors, to understand the mechanisms of tumorigenesis in this rare disease and to develop multi-modality therapies to improve outcomes and decrease treatment-related toxicities. This international cooperation has resulted in a significant leap in our understanding of the molecular pathogenesis of neuroblastoma. Lower staged disease can be cured if the lesion is resectable. Treatment of unresectable disease (loco-regional and metastatic) is stratified depending on clinical features (age at presentation, staging investigations) and specific tumor biological markers that include histopathological analyses, chromosomal abnormalities and the quantification of expression of an oncogene (MYCN). Modern treatment of high-risk neuroblastoma is the paradigm for the evolution of therapy in pediatric oncology. Outcomes have improved substantially with multi-modality therapy, including chemotherapy, surgery, radiation therapy, myeloablative therapy with stem cell transplant, immunotherapy and differentiation therapy; these comprise the standard of care worldwide. In addition, newer targeted therapies are being tested in phase I/II trials. If successful these agents will be incorporated into mainstream treatment programs.

Pediatrics: diagnosis of neuroblastoma

Neuroblastoma is the most common pediatric extracranial soft-tissue tumor, accounting for approximately 8% of childhood malignancies. Its prognosis is widely variable, ranging from spontaneous regression to fatal disease despite multimodality therapy. Multiple imaging and clinical tests are needed to accurately assess patient risk with risk groups based on disease stage, patient age, and biological tumor factors. Approximately 60% of patients with neuroblastoma have metastatic disease, most commonly involving bone marrow or cortical bone. Metaiodobenzylguanidine (mIBG) scintigraphy plays an important role in the assessment of neuroblastoma, allowing whole-body disease assessment. mIBG is used to define extent of disease at diagnosis, assess disease response during therapy, and detect residual and recurrent disease during follow-up. mIBG is highly sensitive and specific for neuroblastoma, concentrating in >90% of tumors. mIBG was initially labeled with (131)I, but (123)I-mIBG yields higher quality images at a lower patient radiation dose. (123)I-mIBG (AdreView; GE Healthcare, Arlington Heights, IL) was approved for clinical use in children by the Food and Drug Administration in 2008 and is now commercially available throughout the United States. The use of single-photon emission computed tomography and single-photon emission computed tomography/computed tomography in (123)I-mIBG imaging has improved certainty of lesion detection and localization. Fluorodeoxyglucose positron-emission tomography has recently been compared with mIBG and found to be most useful in neuroblastomas which fail to or weakly accumulate mIBG.

Comparison of ¹²³I-metaiodobenzylguanidine (MIBG) and ¹³¹I-MIBG semi-quantitative scores in predicting survival in patients with stage 4 neuroblastoma: a report from the Children's Oncology Group

BACKGROUND

¹²³I-metaiodobenzylguanidine (MIBG) scans are preferable to ¹³¹I-MIBG for neuroblastoma imaging as they deliver less patient radiation yet have greater sensitivity in disease detection. Both ¹²³I-MIBG and ¹³¹I-MIBG scans were used for disease assessments of neuroblastoma patients enrolled on Children's Oncology Group (COG) high-risk study A3973. The hypothesis was that ¹²³I-MIBG and ¹³¹I-MIBG scans were sufficiently similar for clinical purposes in terms of ability to predict survival.

PROCEDURE

Patients enrolled on COG A3973 with stage 4 disease who completed ¹²³I-MIBG or ¹³¹I-MIBG scans at diagnosis, post-induction, post-transplant, or post-biotherapy were analyzed. The performance of the Curie score for each MIBG scan type in predicting survival was evaluated. At each time point, survival curves for ¹²³I-MIBG versus ¹³¹I-MIBG were compared using the log-rank test.

RESULTS

Of the 413 patients on A3973 with at least one MIBG scan, 350 were stage 4. The 5-year event-free survival (EFS) and overall survival (OS) rates were 33.4 ± 3.6% and 45.6 ± 4.0% (N = 350). At post-induction, EFS (P = 0.3501) and OS (P = 0.5337) for ¹²³I-MIBG versus ¹³¹I-MIBG were not significantly different. Similarly, comparisons at the three other time points were non-significant.

CONCLUSIONS

We found no evidence of a statistically significant difference in outcome by type of scan. For future survival analyses of MIBG Curie scores, ¹²³I-MIBG and ¹³¹I-MIBG results may be combined and analyzed overall, without adjustment for scan type.

131I/123I-metaiodobenzylguanidine (mIBG) scintigraphy: procedure guidelines for tumour imaging

The aim of this document is to provide general information about mIBG scintigraphy in cancer patients. The guidelines describe the mIBG scintigraphy protocol currently used in clinical routine, but do not include all existing procedures for neuroendocrine tumours. The guidelines should therefore not be taken as exclusive of other nuclear medicine modalities that can be used to obtain comparable results. It is important to remember that the resources and facilities available for patient care may vary from one country to another and from one medical institution to another. The present guidelines have been prepared for nuclear medicine physicians and intend to offer assistance in optimizing the diagnostic information that can currently be obtained from mIBG scintigraphy. The corresponding guidelines of the Society of Nuclear Medicine (SNM) and the Dosimetry, Therapy and Paediatric Committee of the EANM have been taken into consideration, and partially integrated into this text. The same has been done with the most relevant literature on this topic, and the final result has been discussed within a group of distinguished experts.

Criteria for evaluation of disease extent by (123)I-metaiodobenzylguanidine scans in neuroblastoma: a report for the International Neuroblastoma Risk Group (INRG) Task Force

BACKGROUND

Neuroblastoma is an embryonic tumour of the sympathetic nervous system, metastatic in half of the patients at diagnosis, with a high preponderance of osteomedullary disease, making accurate evaluation of metastatic sites and response to therapy challenging. Metaiodobenzylguanidine (mIBG), taken into cells via the norepinephrine transporter, provides a sensitive and specific method of assessing tumour in both soft tissue and bone sites. The goal of this report was to develop consensus guidelines for the use of mIBG scans in staging, response assessment and surveillance in neuroblastoma.

METHODS

The International Neuroblastoma Risk Group (INRG) Task Force, including a multidisciplinary group in paediatric oncology of North and South America, Europe, Oceania and Asia, formed a subcommittee on metastatic disease evaluation, including expert nuclear medicine physicians and oncologists, who developed these guidelines based on their experience and the medical literature, with approval by the larger INRG Task Force.

RESULTS

Guidelines for patient preparation, radiotracer administration, techniques of scanning including timing, energy, specific views, and use of single photon emission computed tomography are included. Optimal timing of scans in relation to therapy and for surveillance is reviewed. Validated semi-quantitative scoring methods in current use are reviewed, with recommendations for use in prognosis and response evaluation.

CONCLUSIONS

Metaiodobenzylguanidine scans are the most sensitive and specific method of staging and response evaluation in neuroblastoma, particularly when used with a semi-quantitative scoring method. Use of the optimal techniques for mIBG in staging and response, including a semi-quantitative score, is essential for evaluation of the efficacy of new therapy.

The prognostic impact of functional imaging with (123)I-mIBG in patients with stage 4 neuroblastoma >1 year of age on a high-risk treatment protocol: results of the German Neuroblastoma Trial NB97

AIM/PURPOSE

(123)I-meta-iodobenzylguanidine ((123)I-mIBG) scintigraphy is well established for staging and evaluation of response in children with high-risk neuroblastoma but its prognostic value in highly intensive first-line treatment protocols is uncertain. The presence of any (123)I-mIBG positive tumour tissue was correlated with event-free survival (EFS) and overall survival (OS).

PATIENTS AND METHODS

The prognostic impact of residual (123)I-mIBG uptake into the primary tumour and metastases for predicting outcome in 113 stage 4 neuroblastoma patients >1 year of the German Neuroblastoma Trial NB97 was assessed using a univariate log-rank test and multivariate Cox regression analysis.

RESULTS

All patients had (123)I-mIBG positive disease at initial staging. After four courses of induction chemotherapy, 71% of patients were still (123)I-mIBG positive for the primary tumour and 61% for metastases. After six courses, 39% of patients had (123)I-mIBG uptake by the primary tumour and 45% residual (123)I-mIBG positive metastatic disease. The (123)I-mIBG status of the primary tumour site had no bearing on outcome. Residual (123)I-mIBG positive metastatic disease after four (3-y-EFS 25.7+/-5.3% versus 55.9+/-7.6%, p=0.009; 3-y-OS 49.8+/-6.1% versus 65.0+/-7.3%; p=0.021) and after six chemotherapy cycles (3-y-EFS 27.5+/-6.2% versus 47.4+/-6.4%, p=0.011; 3-y-OS 50.5+/-7.1% vs 60.0+/-6.4%, p=0.031) was associated with poor outcome.

CONCLUSION

Functional imaging with (123)I-mIBG scintigraphy can identify poor responders with any persistent metastatic (123)I-mIBG uptake who are at a high risk of disease relapse. (123)I-mIBG response of the primary tumour site had no bearing on outcome.

Neuroblastoma and other neuroendocrine tumors

Neuroblastoma is the most common extracranial solid tumor of childhood. It commonly presents in children younger than 2 years of age, with 90% being younger than 5 years of age. There is marked variability in clinical behavior ranging from spontaneous regression or differentiation into benign tumors to rapid and progressive fatal disease. Approximately 50% of patients will have metastases at presentation. The management is dependent on age, stage of disease, and biological and biochemical markers. Nuclear medicine plays an important role in the initial staging, as a prognostic indicator, for assessment of response to treatment, and also in therapy. The most common nuclear medicine diagnostic studies are (99m)Tc-disphosphonate bone scintigraphy and (123)I-MIBG (metaiodobenzylguanidine) scintigraphy. Bone scintigraphy has been the main investigational modality to diagnose skeletal metastases. Whole body imaging with (123)I-MIBG has become the preferred diagnostic test because this agent accumulates in neuroblastoma in 90% to 95% of cases and will accumulate in the primary tumor and metastases particularly in bone, bone marrow, lymph nodes, and soft tissues. MIBG can be used to assess therapy response and is a significant prognostic indicator. Other diagnostic techniques include positron emission tomography (PET)/computed tomography, mainly using (18)F-fluorodeoxyglucose. Other more experimental PET agents, as well as radiolabeled antibodies and octreotide, also are being investigated. Therapy has mainly focused on palliation and has been used alone or in combination with chemotherapy in high-risk refractory or relapsed patients. Major attention is being placed on stratification of patients to try and reduce the side effects associated with intensive megatherapy in the low to intermediate risk patients. Neuroendocrine tumors (NETs) are rare in childhood, but nuclear medicine techniques, mainly using MIBG and somatostatin receptor agents, have a role in diagnosis, staging, and a limited role in therapy. Newer radiopharmaceuticals, including PET agents, are being evaluated for the assessment of NET. Nuclear medicine techniques play a major role in the management of neuroblastoma and NET.

Skeletal Involvement in Infants with Neuroblastoma a Quality Control Attempt

Aims and background

In 1994, French authors hypothesized that positive skeletal mIBG spots in infants with stage 4 neuroblastoma were not prognostically unfavorable unless associated to abnormal standard X-ray or CT findings. In 1999, the European Infant Neuroblastoma Study adopted this definition, indeed reducing the number of patients candidate to chemotherapy. Such an approach requires high quality scans and standardized procedures. The present study critically reviewed and assessed the quality of mIBG scans performed in Italian patients enrolled in the European Infant Neuroblastoma Study.

Methods

Three independent nuclear medicine specialists reviewed scans of 25 Italian patients enrolled in Trials 99.2, 99.3, and 99.4 of the European Infant Neuroblastoma Study between January 2000 and September 2002. An arbitrary quality score was attributed to each mIBG scintigraphy, ranging from 1 (less than adequate) to 3 (excellent). One radiologist and 2 oncologists reviewed the X-rays and CT scans and correlated the results with clinical assessment.

Results

The quality of mIBG scans was rated from good to excellent in 15 of 25 cases, poor in 4, and inadequate for diagnostic evaluation in 6. X-rays confirmed the presence of metastases in 3 of 7 cases with mIBG bone uptake. CT scan confirmed skull metastases in 6 of 9 mIBG-positive cases. Discrepancies in scan interpretation, making trial and stage attribution questionable, were found in 2 patients and are discussed.

Conclusions

The quality of mIBG scans proved to be at least acceptable in most Italian pediatric oncology centers. Efforts should be made to further standardize evaluation of the scans. Additional techniques (99mTc scintigraphy, MRI, SPECT) might be useful to help understand the most complex cases.

Evaluation of semi-quantitative scoring system for metaiodobenzylguanidine (mIBG) scans in patients with relapsed neuroblastoma

BACKGROUND

The purpose of this study was to determine the accuracy of two semi-quantitative scoring systems to assess response to (131)I-metaiodobenzylguanidine (mIBG) therapy in recurrent neuroblastoma.

PROCEDURES

Diagnostic mIBG scan pairs (n = 57) were collected for patients who underwent (131)I-mIBG therapy for relapsed neuroblastoma. Two scoring systems were designated: Method 1, which divided the body into nine segments to view osteomedullary lesions with an additional tenth segment to assess soft tissue involvement; and Method 2, which divided the body into seven segments without a corresponding compartment for soft tissue involvement. Four nuclear medicine physicians independently assigned extension and intensity scores utilizing both methods, and separately recorded their impression of whether the post-therapy scan had improved, not changed, or worsened. Inter- and intra-observer concordance and correlation with overall response and progression-free survival (PFS) were performed.

RESULTS

Method 1 produced the highest inter-observer concordance and was used to calculate the relative extension scores (post-therapy score divided by pre-therapy score), which correlated significantly with overall response. Patients who achieved complete response (CR) or partial response (PR) (n = 21) had lower relative extension scores, compared to those without response (P < 0.001). The readers' overall impression associated highly (P < 0.001) with the relative extension scores though results were less quantitative. Concordance was higher if initial scores were >5. Relative extension score did not predict PFS.

CONCLUSION

Semi-quantitative scoring of mIBG scans provides a more reliable method of assessing response in patients with relapsed neuroblastoma than qualitative impression. The reproducibility and high inter-observer concordance makes mIBG score an important component of overall response criteria in patients with recurrent neuroblastoma.

Imaging Evaluation of Pediatric Mediastinal Masses

Mediastinal masses in children are a heterogeneous group of asymptomatic to potentially life-threatening congenital, infectious, or neoplastic lesions that can present complex diagnostic and therapeutic dilemmas. This article presents the imaging features of the common mediastinal masses seen in the pediatric population. Classification of the masses is performed according to the traditional mediastinal compartment model, consisting of the anterior, middle, and posterior mediastinum. This scheme facilitates differentiation of the variety of disorders.

Scintigraphic response by 123I-metaiodobenzylguanidine scan correlates with event-free survival in high-risk neuroblastoma

PURPOSE

To investigate whether response to induction therapy, evaluated by metaiodobenzylguanadine (MIBG) and bone scintigraphy, correlates with event-free survival (EFS) in children with high-risk neuroblastoma (NB).

PATIENTS AND METHODS

Twenty-nine high-risk NB patients were treated prospectively with an intensive induction regimen and consolidated with three cycles of high-dose therapy with peripheral blood stem-cell rescue. The scintigraphic response was evaluated by MIBG and bone scans using a semi-quantitative scoring system. The prognostic significance of the imaging scores at diagnosis and following induction therapy was evaluated.

RESULTS

A trend associating worse 4-year EFS rates for patients with versus without osteomedullary uptake on MIBG scintigraphs at diagnosis was seen (35% +/- 11% v 80% +/- 18%, respectively; P =.13). Similarly, patients with positive bone scans at diagnosis had worse EFS than those with negative scans, although the difference did not receive statistical significance (34% +/- 10% v 83% +/- 15%, respectively; P =.06). However, significantly worse EFS was observed in patients with a postinduction MIBG score of >/= 3 compared to those with scores of less than 3 (0% v 58% +/- 11%; P =.002). There was no correlation between bone scan scores and outcome following induction therapy.

CONCLUSION

MIBG scores >/= 3 following induction therapy identifies a subset of NB patients who are likely to relapse following three cycles of high-dose therapy with peripheral blood stem-cell rescue, local radiotherapy, and 13-cis-retinoic acid. Alternative therapeutic strategies should be considered for patients with a poor response to induction therapy.

Role of iodine-131 MIBG scanning in the management of paediatric patients with neuroblastoma

OBJECTIVES

To evaluate the role of iodine-131 metoiodobenzylguanidine (iodine-131 MIBG) scanning in the management of paediatric patients with neuroblastoma.

SUBJECTS AND METHODS

Forty-three iodine-131 MIBG scans were performed on 26 children, 18 male and 8 female, ranging in age from 8 months to 11 years. Bone scan, computed tomography (CT) images and findings of bone marrow biopsy were compared with the iodine-131 MIBG scan findings.

RESULTS

Of the 26 patients, 18 (69%) showed abnormal iodine-131 MIBG avidity and were proven to have a neural crest tumour on histology. The remaining 8 (31%) patients had normal iodine-131 MIBG scans, and histology showed a malignancy other than a neural crest tumour. Iodine-131 MIBG scans showed the primary site in 16 of 17 patients while CT showed 14 primary sites. In follow-up studies, the results were as follows: iodine-131 MIBG showed no evidence of disease in 4 compared with 3 on CT, persistent disease in 2 on iodine-131 MIBG and 4 on CT; recurrence in 1 on iodine-131 MIBG and 0 on CT; MIBG scans detected double the number of bony lesions compared with bone scans. The findings on iodine-131 MIBG scans and bone marrow biopsy were in agreement in 16/18 cases. Patients in whom iodine-131 MIBG scans showed disease resolution had better clinical outcomes.

CONCLUSION

The findings indicate that iodine-131 MIBG scanning is useful for the diagnosis, staging, evaluation of response to therapy and detection of recurrences in patients with neuroblastoma. It exhibited a clear advantage over CT in detecting the primary site and soft issue metastases and was also superior to bone scanning in detecting skeletal metastases. It also reliably demonstrated bone marrow involvement.

Correlation of early metastatic response by 123I-metaiodobenzylguanidine scintigraphy with overall response and event-free survival in stage IV neuroblastoma

PURPOSE

Metaiodobenzylguanidine (MIBG), specifically taken up in cells of sympathetic origin, provides a highly sensitive and specific indicator for the detection of metastases in neuroblastoma. The aim of this study was to correlate early response to therapy by MIBG scan, using a semiquantitative scoring method, with the end induction response and event-free survival (EFS) rate in stage IV neuroblastoma.

PATIENTS AND METHODS

Seventy-five children older than 1 year and with stage IV neuroblastoma had 123I-MIBG scans at diagnosis, after two and four cycles of induction therapy, and before autologous stem-cell transplantation. The scans were read by two independent observers (concordance > 95%) using a semiquantitative method. Absolute and relative (score divided by initial score) MIBG scores were then correlated with overall pretransplantation response, bone marrow response, and EFS.

RESULTS

The pretransplantation response rate was 81%, and the 3-year EFS rate was 32%, similar to a concomitant group of 375 stage IV patients. The median relative MIBG scores after two, four, and six cycles were 0.5, 0.24, and 0.12, respectively. The probability of having a complete response or very good partial response before transplantation was significantly higher if the relative score after two cycles was < or = 0.5, or, if after four cycles, the relative score was < or = 0.24. Patients with a relative score of < or = 0.5 after two cycles or a score of < or = 0.24 after four cycles had an improved EFS rate (P =.053 and.045, respectively).

CONCLUSION

Semiquantitative MIBG score early in therapy provides valuable prognostic information for overall response and EFS, which may be useful in tailoring treatment.

SPECT/CT in tumor imaging: technical aspects and clinical applications

Diagnostic imaging has gained a major role in the management of patients with cancer and has made a further step forward with the introduction of fusion techniques into the field. This technology provides hybrid images of two independent modalities, a functional scintigraphic technique and an anatomical procedure, yielding a superior imaging study. Scintigraphy is based on the use of single photon or positron emitting tracers providing a description of function or processes, whereas computed tomography (CT), ultrasound, or magnetic resonance imaging (MRI) depict the precise localization and type of morphological changes that have occurred in the lesions. Initial attempts to coregister the functional and anatomical information following acquisition of the two imaging modalities on separate machines, in different sessions, failed to disclose the proper alignment with precise coregistration, in particular for non-head studies, and were associated with patient preparation and mathematical modeling that were too cumbersome to be used on a routine basis. The recent introduction of a hybrid imaging device containing a low dose CT system and a gamma camera on a single gantry enabled the sequential acquisition of the two imaging modalities, with subsequent merging of data into a composite image display. These hybrid studies have led to a revolution in the field of imaging, with highly accurate localization of tumor sites, assessment of invasion into surrounding tissues, and characterization of their functional status.

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.

Nuclear medicine imaging of neuroendocrine tumours

Different tracers have been proposed in nuclear medicine to visualize neuroendocrine tumours: the majority are based on specific uptake mechanisms while some are aspecific. Among the most important gamma-emitting tracers, radiolabelled metaiodobenzylguanidine (123I or 121I-MIBG) and 111In-pentetreotide should be mentioned. In particular. good results can be obtained with 111In-pentetreotide scanning, which visualizes more than 70% of all neuroendocrine tumours and in some indications, as in gastro-entero-pancreatic (GEP) tumours, has a diagnostic sensitivity superior to that of conventional radiological imaging. Radiolabelled monoclonal antibodies have at present only a storical value, while a series of new peptides represent interesting subjects in areas currently being regarded. Positron emission tomography (PET) is a successful modality to detect cancer and recent years, has demonstrated a great diagnostic value in a large series of tumour types. 18F-deoxyglucose (FDG)-PET has also been used to diagnose tumours of neuroendocrine origin. Even if 18F-FDG has been successfully and widely employed in oncology, it has not demostrated a significant uptake in well differentiated neuroendocrine tissues. On the contrary, other positron emitter tracers seem to be more promising. A serotonin precursor 5-hydroxytryptophan (5-HTP) labelled with 11C has shown an increased uptake in carcinoids. This uptake seems to be selective and some clinical evidence has demonstrated that it allows the detection of more lesions with PET than with CT or octreotide scintigraphy. Another radiopharmaceutical in development for PET is 11C L-DOPA, which seems to be useful in visualizing endocrine pancreatic tumours. This Review summarizes the potential of several nuclear medicine techniques in the diagnosis of neuroendocrine tumours and stresses the renewed role of nuclear -medicine in the management of this disease.

Metaiodobenzylguanidine assessment of metastatic neuroblastoma: observer dependency and chemosensitivity evaluation. The SFOP Group

BACKGROUND

In children over 1 year of age with metastatic neuroblastoma, clearance of metaiodobenzylguanidine (MIBG) skeletal uptake after four courses of induction chemotherapy is one of the most powerful prognostic factors. How subjective is quantification of MIBG uptake, and can earlier MIBG scintigraphy separate good and bad responders?

PROCEDURE

The data from 47 patients who received uniform induction therapy were reviewed. A novel scoring system of MIBG update intensity was proposed. Initial, intermediate (after two courses), and final (after four courses) intensities were scored (0 to 21 points) independently by six different observers. The initial global score and the relative score (calculated by dividing the global score after two courses by the initial score) were compared to the final score. Good responders were those who scored 0 at final MIBG.

RESULTS

Between two observers, the correlation coefficient for the global score was superior to 0.80, in nine of ten comparisons established between observers 1-5. The initial score did not predict the final score insofar as only nine of fourteen patients with low initial scores were good responders. The relative score also failed to predict outcome; only six of ten patients with favorable relative score (i.e., <20%), were good responders.

CONCLUSIONS

This scoring system is reliable and may be used in multicentric trials. However, both initial and relative scores failed to predict final outcome. Thus, intermediate MIBG may be omitted during induction therapy assessment.

Current aspects of biology, risk assessment, and treatment of neuroblastoma

Neuroblastoma is one of the most intensely studied solid malignancies that affect the pediatric age groups; its clinical presentation, treatment strategies and ultimate prognosis vary greatly. The biologic and genetic character of each tumor has an important impact on disease behavior, and clinical staging now incorporates these factors to generate an overall therapy plan. The clinical presentation of neuroblastoma is related to primary tumor location, production of metabolically active substances, and the presence of metastatic disease. There are also prognostically important associated syndromes including opsoclonus-myoclonus, Horner's syndrome, neurofibromatosis, and a variety of other neurocristopathies. The histologic features of the tumor are of prognostic significance and are utilized in treatment stratification. The International Neuroblastoma Staging System (INSS) has unified classic clinical staging. Features at diagnosis and those determined by initial operation are combined with biologic prognostic factors to achieve risk group assignment for virtually all patients. There are groups of children in which limited therapy is curative and intermediate-risk situations where standard multimodality treatment provides favorable outcomes. Unfortunately, there are many patients with high-risk disease that require intensive strategies, but success is still limited. It is in these most resistant patients that innovative approaches are being undertaken and novel strategies are being investigated.

Clinical impact and prognostic value of metaiodobenzylguanidine imaging in children with metastatic neuroblastoma

PURPOSE

The clinical value of metaiodobenzylguanidine (mIBG) scintigraphy in patients with disseminated neuroblastoma (NB) at the time of diagnosis and after induction chemotherapy was evaluated.

PATIENTS AND METHODS

The medical records and imaging studies of 30 patients with stage 4 NB who underwent mIBG scintigraphy and 99mTc hydroxy methylene diphosphonate bone scintigraphy at the time of diagnosis were reviewed. Scores were calculated for the mIBG and bone scintigrams, and outcome according to the initial and follow-up imaging studies was determined.

RESULTS

Discrepancies between bone scintigraphy and mIBG osteomedullary localization were seen in six patients. For the entire cohort, 2-year event-free survival did not significantly differ for the group of patients with initial mIBG or bone scintigraphy scores > or = 10 compared to those with scores < 10 (P = 0.23 and 0.61, respectively). However, for patients older than 1 year, a trend associating worse outcome with mIBG scores > or = 10 at diagnosis was seen (P = 0.08). A trend correlating abnormal mIBG scintigraphy after induction therapy and poor outcome was also observed (P = 0.09). Outcome did not correlate with the results of the bone scintigram studies performed after induction chemotherapy (P = 0.68).

CONCLUSION

Because a discordance between mIBG and bone scintigraphy results were seen in a subset of stage 4 NB patients, both imaging studies should be performed at the time of diagnosis. mIBG imaging studies performed at the time of diagnosis and after induction chemotherapy may be of prognostic value, particularly in stage 4 patients older than 1 year.