Comparison of iodine-123 metaiodobenzylguanidine (MIBG) scan and [18F]fluorodeoxyglucose positron emission tomography to evaluate response after iodine-131 MIBG therapy for relapsed neuroblastoma

The prognostic role of 18F-FDG PET/CT-based response evaluation in children with stage 4 neuroblastoma

OBJECTIVES

To evaluate the association between metabolic response on 18F-FDG PET/CT and long-term survival in children with neuroblastoma (NB).

METHODS

A total of 39 consecutive children with newly diagnosed stage 4 NB undergoing both 18F-FDG PET/CT imaging at baseline and after chemotherapy were retrospectively analyzed. The associations between metabolic parameters, including SUVmax of the lesion with the most intense 18F-FDG uptake at baseline (SUVb), after chemotherapy (SUVe), and the percentage change between SUVb and SUVe, and long-term survival were evaluated.

RESULTS

With a median follow-up of 56 months, 22 patients who had achieved complete resolution on PET (no residual 18F-FDG uptake higher than the surrounding backgrounds) after chemotherapy had superior 5-year overall survival (OS) (73.6% vs. 39.0%, p = 0.044). SUVb > 6.9 indicated significantly poorer 5-year event-free survival (EFS) (12.5% vs. 59.3%, p = 0.005), as did SUVe > 1.2 (18.8% vs. 41.7%, p = 0.041). Children with SUVe > 1.2 had shorter 5-year OS (33.9% vs. 75.0%, p = 0.018). Multivariate analysis identified SUVe > 1.2 as an independent predictor for both EFS [hazard ratio (HR), 3.479, 95% CI, 1.381-8.761, p = 0.008] and OS (HR, 6.948, 95% CI, 1.663-29.025, p = 0.008), while SUVb > 6.9 was a predictor for EFS (HR, 2.889, 95% CI, 1.064-7.842, p = 0.037). Among 11 children with both SUVb > 6.9 and SUVe > 1.2, all experienced disease progression or relapse within 2 years since diagnosis.

CONCLUSION

18F-FDG PET/CT could be of useful to evaluate treatment response in children with stage 4 NB.

CLINICAL RELEVANCE STATEMENT

18F-FDG PET/CT after chemotherapy exhibits prognostic significance in neuroblastoma and holds potential as an alternative imaging modality for response evaluation, especially in cases with metaiodobenzylguanidine-nonavid or persistent avid disease.

KEY POINTS

The prognostic value of chemotherapy response on 18F-FDG PET/CT in advanced neuroblastoma is unknown. Higher 18F-FDG uptake after chemotherapy was associated with worse long-term event-free survival and overall survival. 18F-FDG PET/CT after chemotherapy holds prognostic significance in children with stage 4 neuroblastoma.

18F-FDG PET/CT-Based Radiomics Nomogram for Prediction of Bone Marrow Involvement in Pediatric Neuroblastoma: A Two-Center Study

RATIONALE AND OBJECTIVES

To assess the predictive ability of an 18F-FDG PET/CT-based radiomics nomogram for bone marrow involvement in pediatric neuroblastoma.

MATERIALS AND METHODS

A total of 241 neuroblastoma patients who underwent 18F-FDG PET/CT at two medical centers were retrospectively evaluated. Data from center A (n = 200) were randomized into a training cohort (n = 140) and an internal validation cohort (n = 60), while data from center B (n = 41) constituted the external validation cohort. For each patient, two regions of interest were defined using the tumor and axial skeleton. The clinical factors and radiomics features were derived to construct the clinical and radiomics models. The radiomics nomogram was built by combining clinical factors and radiomics features. The area under the receiver operating characteristic curves (AUCs) were used to assess the performance of the models.

RESULTS

Radiomics models created from tumor and axial skeleton achieved AUCs of 0.773 and 0.900, and the clinical model had an AUC of 0.858 in the training cohort. By incorporating clinical risk factors and axial skeleton-based radiomics features, the AUC of the radiomics nomogram in the training cohort, internal validation cohort, and external validation cohort was 0.932, 0.887, and 0.733, respectively.

CONCLUSION

The axial skeleton-based radiomics model performed better than the tumor-based radiomics model in predicting bone marrow involvement. Moreover, the radiomics nomogram showed that combining axial skeleton-based radiomics features with clinical risk factors improved their performance.

The evidence-based role of catecholaminergic PET tracers in Neuroblastoma. A systematic review and a head-to-head comparison with mIBG scintigraphy

BACKGROUND

Molecular imaging is pivotal in staging and response assessment of children with neuroblastoma (NB). [123I]-metaiodobenzylguanidine (mIBG) is the standard imaging method; however, it is characterised by low spatial resolution, time-consuming acquisition procedures and difficult interpretation. Many PET catecholaminergic radiotracers have been proposed as a replacement for [123I]-mIBG, however they have not yet made it into clinical practice. We aimed to review the available literature comparing head-to-head [123I]-mIBG with the most common PET catecholaminergic radiopharmaceuticals.

METHODS

We searched the PubMed database for studies performing a head-to-head comparison between [123I]-mIBG and PET radiopharmaceuticals including meta-hydroxyephedrine ([11C]C-HED), 18F-18F-3,4-dihydroxyphenylalanine ([18F]DOPA) [124I]mIBG and Meta-[18F]fluorobenzylguanidine ([18F]mFBG). Review articles, preclinical studies, small case series (< 5 subjects), case reports, and articles not in English were excluded. From each study, the following characteristics were extracted: bibliographic information, technical parameters, and the sensitivity of the procedure according to a patient-based analysis (PBA) and a lesion-based analysis (LBA).

RESULTS

Ten studies were selected: two regarding [11C]C-HED, four [18F]DOPA, one [124I]mIBG, and three [18F]mFBG. These studies included 181 patients (range 5-46). For the PBA, the superiority of the PET method was reported in two out of ten studies (both using [18F]DOPA). For LBA, PET detected significantly more lesions than scintigraphy in seven out of ten studies.

CONCLUSIONS

PET/CT using catecholaminergic tracers shows superior diagnostic performance than mIBG scintigraphy. However, it is still unknown if such superiority can influence clinical decision-making. Nonetheless, the PET examination appears promising for clinical practice as it offers faster image acquisition, less need for sedation, and a single-day examination.

Current Status and Future Perspective on Molecular Imaging and Treatment of Neuroblastoma

Neuroblastoma is the most common extracranial solid tumor in children and arises from anywhere along the sympathetic nervous system. It is a highly heterogeneous disease with a wide range of prognosis, from spontaneous regression or maturing to highly aggressive. About half of pediatric neuroblastoma patients develop the metastatic disease at diagnosis, which carries a poor prognosis. Nuclear medicine plays a pivotal role in the diagnosis, staging, response assessment, and long-term follow-up of neuroblastoma. And it has also played a prominent role in the treatment of neuroblastoma. Because the structure of metaiodobenzylguanidine (MIBG) is similar to that of norepinephrine, 90% of neuroblastomas are MIBG-avid. 123I-MIBG whole-body scintigraphy is the standard nuclear imaging technique for neuroblastoma, usually in combination with SPECT/CT. However, approximately 10% of neuroblastomas are MIBG nonavid. PET imaging has many technical advantages over SPECT imaging, such as higher spatial and temporal resolution, higher sensitivity, superior quantitative capability, and whole-body tomographic imaging. In recent years, various tracers have been used for imaging neuroblastoma with PET. The importance of patient-specific targeted radionuclide therapy for neuroblastoma therapy has also increased. 131I-MIBG therapy is part of the front-line treatment for children with high-risk neuroblastoma. And peptide receptor radionuclide therapy with radionuclide-labeled somatostatin analogues has been successfully used in the therapy of neuroblastoma. Moreover, radioimmunoimaging has important applications in the diagnosis of neuroblastoma, and radioimmunotherapy may provide a novel treatment modality against neuroblastoma. This review discusses the use of current and novel radiopharmaceuticals in nuclear medicine imaging and therapy of neuroblastoma.

Imaging of pediatric neuroblastoma: A COG Diagnostic Imaging Committee/SPR Oncology Committee White Paper

Neuroblastoma is the most common extracranial solid neoplasm in children. This manuscript provides consensus-based imaging recommendations for pediatric neuroblastoma patients at diagnosis and during follow-up.

Comparing the diagnostic value of 18F-FDG PET/CT scan and bone marrow biopsy in newly diagnosed pediatric neuroblastoma and ganglioneuroblastoma

Objective

This study aims to compare the diagnostic value of ¹⁸F-fluorodeoxyglucose (18-FDG) positron emission tomography (PET)/computed tomography (CT) (¹⁸F-FDG PET/CT) scan and bone marrow biopsy (BMB) for evaluating bone marrow infiltration (BMI) in newly diagnosed pediatric neuroblastoma (NB) and ganglioneuroblastoma (GNB).

Methods

We retrospectively reviewed 51 patients with newly diagnosed NB and GNB between June 1, 2019 and May 31, 2022. Each patient had undergone ¹⁸F-FDG PET/CT and BMB within 1 week and received no treatment. Clinical data were collected and statistically analyzed, including age, sex, pathologic type, and laboratory parameters. ¹⁸F-FDG PET/CT and BMB revealed the result of bone lesions.

Results

A concordance analysis showed that, in this study population, ¹⁸F-FDG PET/CT and BMB were in moderate agreement (Cohen's Kappa = 0.444; p = 0.001), with an absolute agreement consistency of 72.5% (37 of 51). The analysis of the receiver operating characteristic (ROC) curve determined that the areas under the ROC curve (AUCs) of SUV_BM and SUV/HE-SUVmax were 0.971 (95% CI: 0.911-1.000; p < 0.001) and 0.917 (95% CI: 0.715-1.000; p < 0.001) to predict bone-bone marrow involvement (BMI), respectively.

Conclusion

¹⁸F-FDG PET/CT detects BMI with good diagnostic accuracy and can reduce unnecessary invasive inspections in newly diagnosed pediatric NB and GNB, especially patterns C and D. The analysis of the semi-quantitative uptake of ¹⁸F-FDG, including SUV_BM and SUV_BM/HE-SUVmax, enables an effective differentiation between patterns A and B.

Integration of molecular imaging in the personalized approach to neuroendocrine tumors

NETs lesions can be difficult to characterize with conventional anatomic imaging (CT and MRI). Functional imaging techniques, and especially PET imaging, are very useful for detecting small neuroendocrine tumors that would not be seen with other techniques. The role of nuclear medicine in the localization, staging, restaging, treatment and monitoring of neuroendocrine tumors (NETs) has become progressively more relevant due to: the availability of tracers on new targets, tracers for positron emission tomography (PET); the development of cyclotrons and generators that allow this availability; as well as to hybrid systems (SPECT/CT, PET/CT and PET/MRI) that, by joining the functional and anatomical image, improve the quality of the images. Teragnosis, a new emerging therapy, in NET used receptor-mediated or nonreceptor- mediated mechanism to facilitate penetration and high-affinity binding between the radiopharmaceutical and the tumor cell. Teragnosis offers the possibility of personalized targeted radionuclide therapy.

The role of microscopic bone marrow examination and [123I]MIBG scintigraphy in detection of bone marrow involvement in patients with neuroblastoma

OBJECTIVES

For the detection of bone marrow (BM) metastases in patients with neuroblastoma, microscopic BM examination and [¹²³I]MIBG scintigraphy are advised. The aims of this study were to assess the concordance of [¹²³I]MIBG and microscopic BM examination (aspirate and biopsy) in detecting BM involvement and to compare invasive disease in BM biopsies and aspirates, both at diagnosis and before autologous stem cell collection (ASCC).

METHODS

Fifty-five patients with stage 4 or stage 4S disease were included, and 37 of them received an autologous hematopoietic stem cell transplantation (AHSCT). The concordance rate was measured and paired binary data were analysed by the McNemar test to look for a systematic difference between diagnostic tests.

RESULTS

At diagnosis and before ASCC, we found acceptable concordance rates for [¹²³I]MIBG versus microscopic BM examination (77.1% and 85.3% respectively). Discordant results were found in both directions and at both time points. The concordance rate for biopsy versus aspirate at diagnosis was 80.6%, however, before ASCC a much higher concordance rate between both microscopic examinations was found (94.1%). While none of the aspirates showed neuroblastoma cells before ASCC, two biopsies still showed tumor invasion.

CONCLUSION

For patients with neuroblastoma, a [¹²³I]MIBG scintigraphy and a microscopic examination of BM aspirate and its biopsy should be used as complementary tools in the evaluation of BM involvement, and this both at diagnosis and during treatment (before ASCC).

Diagnostic Value of Seven Different Imaging Modalities for Patients with Neuroblastic Tumors: A Network Meta-Analysis

Objective

We performed a systematic review and network meta-analysis (NMA) to compare the diagnostic value of seven different imaging modalities for the detection of neuroblastic tumors in diverse clinical settings.

Methods

PubMed, Embase, Medline, and the Cochrane Library were searched to identify eligible studies from inception to Sep 29, 2020. Quality assessment of included studies was appraised with Quality Assessment of Diagnostic Accuracy Studies. Firstly, direct pairwise meta-analysis was conducted to calculate the pooled estimates of odds ratio (OR) and 95% confidence interval (CI) of the sensitivity, specificity, NPV, PPV, and DR. Next, NMA using Bayesian methods was performed. The superiority index was assessed to quantify the rank probability of a diagnostic test. The studies performed SPECT/CT or SPECT were analyzed separately from the ones only performed planar imaging.

Results

A total of 1135 patients from 32 studies, including 7 different imaging modalities, were eligible for this NMA. In the pairwise meta-analysis, ¹⁸F-FDOPA PET/CT had a relatively high value of all the outcomes (sensitivity: 10.195 [5.332–19.493]; specificity: 17.906 [5.950–53.884]; NPV: 16.819 [7.033–40.218]; PPV: 11.154 [4.216–29.512]; and DR 5.616 [3.609–8.739]). In the NMA, ¹⁸F-FDOPA PET/CT exhibited relatively high sensitivity in all subgroups (all data: 0.94 [0.87–0.98]; primary tumor: 0.89 [0.53–1]; bone/bone marrow metastases: 0.96 [0.83–1]; and primary tumor and metastases (P + M): 0.92 [0.80–0.97]), the highest specificity in the subgroup of P + M (0.85 [0.61–0.97]), and achieved the highest superiority index in the subgroups of all data (8.57 [1–15]) and P + M (7.25 [1–13]).

Conclusion

¹⁸F-FDOPA PET/CT exhibited the best diagnostic performance in the comprehensive detection of primary tumor and metastases for neuroblastic tumors, followed by ⁶⁸Ga-somatostatin analogs, ¹²³I-meta-iodobenzylguanidine (MIBG), ¹⁸F-FDG, and ¹³¹I-MIBG tomographic imaging.

Diagnostic Performance of 18F-FDG PET(CT) in Bone-Bone Marrow Involvement in Pediatric Neuroblastoma: A Systemic Review and Meta-Analysis

Objective

We sought to perform a systemic review and meta-analysis of the diagnostic performance of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (computed tomography) (PET(CT)) in detection of bone and/or bone marrow involvement (BMI) in pediatric neuroblastoma (NB).

Materials and Methods

We searched electronic databases Pubmed and Embase to retrieve relevant references. We calculated pooled sensitivity, specificity, positive and negative likelihood ratios (LR+ and LR−), diagnostic odds ratio (DOR), and the area under the curve (AUC). Moreover, a summary receiver operating characteristic (SROC) curve and likelihood ratio dot plot were plotted. Study-between statistical heterogeneity was evaluated via I-square index (I²). Subgroup analyses were used to explore heterogeneity.

Results

Seven studies including 127 patients were involved in this meta-analysis. The overall sensitivity and specificity were 0.87 (95% CI: 0.65–0.96) with heterogeneity I² = 88.1% (p < 0.001) and 0.96 (95% CI: 0.67–1.00) with heterogeneity I² = 77.8% (p < 0.001), respectively. The pooled LR+, LR−, and DOR were 21.3 (95% CI: 2.1–213.9), 0.14 (95% CI: 0.05–0.40), and 157 (95% CI: 16–1532), respectively. The area under the SROC curve was 0.97 (95% CI: 0.95–0.98).

Conclusions

Through a meta-analysis, this study suggested that ¹⁸F-FDG PET(CT) has a good overall diagnostic accuracy in the detection of bone/BMI in pediatric neuroblastoma.

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.

Nuclear Medicine Imaging in Neuroblastoma: Current Status and New Developments

Neuroblastoma is the most common extracranial solid malignancy in children. At diagnosis, approximately 50% of patients present with metastatic disease. These patients are at high risk for refractory or recurrent disease, which conveys a very poor prognosis. During the past decades, nuclear medicine has been essential for the staging and response assessment of neuroblastoma. Currently, the standard nuclear imaging technique is meta-[¹²³I]iodobenzylguanidine ([¹²³I]mIBG) whole-body scintigraphy, usually combined with single-photon emission computed tomography with computed tomography (SPECT-CT). Nevertheless, 10% of neuroblastomas are mIBG non-avid and [¹²³I]mIBG imaging has relatively low spatial resolution, resulting in limited sensitivity for smaller lesions. More accurate methods to assess full disease extent are needed in order to optimize treatment strategies. Advances in nuclear medicine have led to the introduction of radiotracers compatible for positron emission tomography (PET) imaging in neuroblastoma, such as [¹²⁴I]mIBG, [¹⁸F]mFBG, [¹⁸F]FDG, [⁶⁸Ga]Ga-DOTA peptides, [¹⁸F]F-DOPA, and [¹¹C]mHED. PET has multiple advantages over SPECT, including a superior resolution and whole-body tomographic range. This article reviews the use, characteristics, diagnostic accuracy, advantages, and limitations of current and new tracers for nuclear medicine imaging in neuroblastoma.

Poverty and Targeted Immunotherapy: Survival in Children's Oncology Group Clinical Trials for High-Risk Neuroblastoma

BACKGROUND

Whether social determinants of health are associated with survival in the context of pediatric oncology-targeted immunotherapy trials is not known. We examined the association between poverty and event-free survival (EFS) and overall survival (OS) for children with high-risk neuroblastoma treated in targeted immunotherapy trials.

METHODS

We conducted a retrospective cohort study of 371 children with high-risk neuroblastoma treated with GD2-targeted immunotherapy in the Children's Oncology Group trial ANBL0032 or ANBL0931 at a Pediatric Health Information System center from 2005 to 2014. Neighborhood poverty exposure was characterized a priori as living in a zip code with a median household income within the lowest quartile for the cohort. Household poverty exposure was characterized a priori as sole coverage by public insurance. Post hoc analyses examined the joint effect of neighborhood and household poverty using a common reference. All statistical tests were 2-sided.

RESULTS

In multivariable Cox regressions adjusted for disease and treatment factors, household poverty-exposed children experienced statistically significantly inferior EFS (hazard ratio [HR] = 1.90, 95% confidence interval [CI] = 1.28 to 2.82, P = .001) and OS (HR = 2.79, 95% CI = 1.63 to 4.79, P < .001) compared with unexposed children. Neighborhood poverty was not independently associated with EFS or OS. In post hoc analyses exploring the joint effect of neighborhood and household poverty, children with dual-poverty exposure (neighborhood poverty and household poverty) experienced statistically significantly inferior EFS (HR = 2.21, 95% CI = 1.48 to 3.30, P < .001) and OS (HR = 3.70, 95% CI = 2.08 to 6.59, P < .001) compared with the unexposed group.

CONCLUSIONS

Poverty is independently associated with increased risk of relapse and death among neuroblastoma patients treated with targeted immunotherapy. Incorporation of social and environmental factors in future trials as health-care delivery intervention targets may increase the benefit of targeted therapies.

The Complementary Role of 68Ga-DOTATATE PET/CT in Neuroblastoma

A girl diagnosed with neuroblastoma at 33 months underwent I-MIBG scan after surgery and chemoradiotherapy. Although MIBG scan showed complete response, the bone marrow biopsy showed refractory disease. Therefore, she underwent Ga-DOTATATE PET/CT, which revealed bone marrow involvement and Ga-DOTATATE-avid brain metastasis. Rare physiological pineal gland uptake was also depicted. Ga-DOTATATE PET/CT showed active progressive disease earlier, before it was detectable with MIBG scan. For patients with MIBG-negative relapsed/refractory disease, Ga-DOTATATE may have an important role in restaging, detecting unsuspected metastasis, therapy planning.

18F-FDG PET-CT in paediatric oncology: established and emerging applications

Accurate staging and response assessment is vital in the management of childhood malignancies. Fluorine-18 fluorodeoxyglucose positron emission tomography/CT (FDG PET-CT) provides complimentary anatomical and functional information. Oncological applications of FDG PET-CT are not as well-established within the paediatric population compared to adults. This article will comprehensively review established oncological PET-CT applications in paediatric oncology and provide an overview of emerging and future developments in this domain.

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.

Current status of functional imaging in neuroblastoma, pheochromocytoma, and paraganglioma disease

Diagnostic imaging plays an important role in the detection of paraganglioma (PGL), pheochromocytoma (PCC), and neuroblastoma (NB). Anatomic imaging, for example CT or MRI, offers high sensitivity in these neuroendocrine tumors (NET) but only moderate specificity, often associated with difficulties in clearly distinguishing between NET and non-NET. Functional imaging, as in the use of different radioisotopes, is indispensable in oncological imaging. The introduction of PET and PET/CT, respectively, led to a dramatic improvement in both malignant and non-malignant PGL, PCC, and NB, assessing the exact tumor extent. This review gives an overview of functional and anatomical imaging in PGL, PCC, and NB.

Evaluation of the utility of 99m Tc-MDP bone scintigraphy versus MIBG scintigraphy and cross-sectional imaging for staging patients with neuroblastoma

PURPOSE

Accurate staging of neuroblastoma requires multiple imaging examinations. The purpose of this study was to determine the relative contribution of ^99m Tc-methylene diphosphonate (MDP) bone scintigraphy (bone scan) versus metaiodobenzylguanidine scintigraphy (MIBG scan) for accurate staging of neuroblastoma.

METHODS

A medical record search by the identified patients with neuroblastoma from 1993 to 2012 who underwent both MIBG and bone scan for disease staging. Cross-sectional imaging was used to corroborate the scintigraphy results. Clinical records were used to correlate imaging findings with clinical staging and patient management.

RESULTS

One hundred thirty-two patients underwent both MIBG and bone scan for diagnosis. All stage 1 (n = 12), 2 (n = 8), and 4S (n = 4) patients had a normal bone scan with no skeletal MIBG uptake. Six of 30 stage 3 patients had false (+) bone scans. In the 78 stage 4 patients, 58/78 (74%) were both skeletal MIBG(+)/bone scan (+). In 56 of the 58 cases, skeletal involvement detected with MIBG was equal to or greater than that detected by bone scan. Only 3/78 had (-) skeletal MIBG uptake and (+) bone scans; all 3 had other sites of metastatic disease. Five of 78 had (+) skeletal MIBG with a (-) bone scan, while 12/78 had no skeletal involvement by either MIBG or bone scan. In no case did a positive bone scan alone determine a stage 4 designation.

CONCLUSION

In the staging of neuroblastoma, ^99m Tc-MDP bone scintigraphy does not identify unique sites of disease that affect disease stage or clinical management, and in the majority of cases bone scans can be omitted from the routine neuroblastoma staging algorithm.

Comparison of diagnosing and staging accuracy of PET (CT) and MIBG on patients with neuroblastoma: Systemic review and meta-analysis

To perform a systemic review and meta-analysis of the diagnostic accuracy of PET (CT) and metaiodobenzylguanidine (MIBG) for diagnosing neuroblastoma (NB), electronic databases were searched as well as relevant references and conference proceedings. The diagnostic accuracy of MIBG and PET (CT) was calculated for NB, primary NB, and relapse/metastasis of NB based on their sensitivity, specificity, and area under the summary receiver operating characteristic curve (AUSROC) in terms of per-lesion and per-patient data. A total of 40 eligible studies comprising 1134 patients with 939 NB lesions were considered for the meta-analysis. For the staging of NB, the per-lesion AUSROC value of MIBG was lower than that of PET (CT) [0.8064±0.0414 vs. 0.9366±0.0166 (P<0.05)]. The per-patient AUSROC value of MIBG and PET (CT) for the diagnosis of NB was 0.8771±0.0230 and 0.6851±0.2111, respectively. The summary sensitivity for MIBG and PET (CT) was 0.79 and 0.89, respectively. The summary specificity for MIBG and PET (CT) was 0.84 and 0.71, respectively. PET (CT) showed higher per-lesion accuracy than MIBG and might be the preferred modality for the staging of NB. On the other hand, MIBG has a comparable diagnosing performance with PET (CT) in per-patient analysis but shows a better specificity.

Norepinephrine Transporter as a Target for Imaging and Therapy

The norepinephrine transporter (NET) is essential for norepinephrine uptake at the synaptic terminals and adrenal chromaffin cells. In neuroendocrine tumors, NET can be targeted for imaging as well as therapy. One of the most widely used theranostic agents targeting NET is metaiodobenzylguanidine (MIBG), a guanethidine analog of norepinephrine. ¹²³I/¹³¹I-MIBG theranostics have been applied in the clinical evaluation and management of neuroendocrine tumors, especially in neuroblastoma, paraganglioma, and pheochromocytoma. ¹²³I-MIBG imaging is a mainstay in the evaluation of neuroblastoma, and ¹³¹I-MIBG has been used for the treatment of relapsed high-risk neuroblastoma for several years, however, the outcome remains suboptimal. ¹³¹I-MIBG has essentially been only palliative in paraganglioma/pheochromocytoma patients. Various techniques of improving therapeutic outcomes, such as dosimetric estimations, high-dose therapies, multiple fractionated administration and combination therapy with radiation sensitizers, chemotherapy, and other radionuclide therapies, are being evaluated. PET tracers targeting NET appear promising and may be more convenient options for the imaging and assessment after treatment. Here, we present an overview of NET as a target for theranostics; review its current role in some neuroendocrine tumors, such as neuroblastoma, paraganglioma/pheochromocytoma, and carcinoids; and discuss approaches to improving targeting and theranostic outcomes.

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.

Nuclear Medicine in Pediatric and Adolescent Tumors

Nuclear medicine has an important role in the management of many cancers in pediatric age group with multiple imaging modalities and radiopharmaceuticals targeting various biological uptake mechanisms. 18-Flourodeoxyglucose is the radiotracer of choice especially in patients with sarcoma and lymphoma. (18)FDG-PET, for sarcoma and lymphomas, is proved to be superior to conventional imaging in staging and therapy response. Although studies are limited in pediatric population, (18)FDG-PET/CT has found its way through international guidelines. Limitations and strengths of PET imaging must be noticed before adapting PET imaging in clinical protocols. Established new response criteria using multiple parameters derived from (18)FDG-PET would increase the accuracy and repeatability of response evaluation. Current data suggest that I-123 metaiodobenzylguanidine (MIBG) remains the tracer of choice in the evaluation of neuroblastoma (NB) because of its high sensitivity, specificity, diagnostic accuracy, and prognostic value. It is valuable in determining the response to therapy, surveillance for disease recurrence, and in selecting patients for I-131 therapy. SPECT/CT improves the diagnostic accuracy and the interpretation confidence of MIBG scans. (18)FDG-PET/CT is an important complementary to MIBG imaging despite its lack of specificity to NB. It is valuable in cases of negative or inconclusive MIBG scans and when MIBG findings underestimate the disease status as determined from clinical and radiological findings. F-18 DOPA is promising tracer that reflects catecholamine metabolism and is both sensitive and specific. F-18 DOPA scintigraphy provides the advantages of PET/CT imaging with early and short imaging times, high spatial resolution, inherent morphologic correlation with CT, and quantitation. Regulatory and production issues currently limit the tracer's availability. PET/CT with Ga-68 DOTA appears to be useful in NB imaging and may have a unique role in selecting patients for peptide receptor radionuclide therapy with somatostatin analogues. C-11 hydroxyephedrine PET/CT is a specific PET tracer for NB, but the C-11 label that requires an on-site cyclotron production and the high physiologic uptake in the liver and kidneys limit its use. I-124 MIBG is useful for I-131 MIBG pretherapeutic dosimetry planning. Its use for diagnostic imaging as well as the use of F-18 labeled MIBG analogues is currently experimental. PET/MR imaging is emerging and is likely to become an important tool in the evaluation. It provides metabolic and superior morphological data in one imaging session, expediting the diagnosis and lowering the radiation exposure. Radioactive iodines not only detect residual tissue and metastatic disease but also are used in the treatment of differentiated thyroid cancer. However, these are not well documented in pediatric age group like adult patients. Use of radioactivity in pediatric population is very important and strictly controlled because of the possibility of secondary malignities; therefore, management of oncological cases requires detailed literature knowledge. This article aims to review the literature on the use of radionuclide imaging and therapy in pediatric population with thyroid cancer, sarcomas, lymphoma, and NB.

Overview and recent advances in the treatment of neuroblastoma

INTRODUCTION

Children with neuroblastoma have widely divergent outcomes, ranging from cure in >90% of patients with low risk disease to <50% for those with high risk disease. Recent research has shed light on the biology of neuroblastoma, allowing for more accurate risk stratification and treatment reduction in many cases, although newer treatment strategies for children with high-risk and relapsed neuroblastoma are needed to improve outcomes. Areas covered: Neuroblastoma epidemiology, diagnosis, risk stratification, and recent advances in treatment of both newly diagnosed and relapsed neuroblastoma. Expert commentary: The identification of newer tumor targets and of novel cell-mediated immunotherapy agents may lead to novel therapeutic approaches, and clinical trials for regimens designed to target individual genetic aberrations in tumors are underway. A combination of therapeutic modalities will likely be required to improve survival and cure rates for patients with high-risk neuroblastoma.

Risk Stratification of Pediatric Patients With Neuroblastoma Using Volumetric Parameters of 18F-FDG and 18F-DOPA PET/CT

PURPOSE

This study determined the prognostic value of volumetric parameters derived from pretreatment F-FDG and F-DOPA PET/CT of neuroblastoma and their correlation with clinical and histopathologic features.

PATIENTS AND METHODS

A total of 25 children with neuroblastoma underwent pretreatment F-FDG and F-DOPA PET/CT within 4 weeks. The SUVmax of primary tumors on F-FDG and F-DOPA PET were recorded as SUVFDG and SUVDOPA, respectively. For volumetric parameters of primary tumors, 40% of SUVmax was used to generate volume of interest. If the 40% of SUVmax was below 2.5, an SUV threshold of 2.5 was used instead. Metabolic tumor volume (MTV), total lesion glycolysis (TLG), dopaminergic tumor volume (DTV), and total lesion F-DOPA activity (TLDA) were recorded as F-FDG and F-DOPA volumetric parameters. All indices were compared between groups distinguished by survival status and clinical features, including bone marrow involvement, lymph node metastasis, amplification of the MYCN oncogene, invasive features on anatomic images, and risk categories. The Kaplan-Meier method and log-rank test were used to compare the survival curves between groups.

RESULTS

The median follow-up period was 28.2 months. Nonsurvivors (20%) tended to have lower SUVDOPA, DTV, and TLDA (P ≤ 0.05), and higher SUVFDG, MTV, and TLG (all P < 0.05). Lower F-DOPA uptake is associated with bone marrow and lymph node metastases (all P < 0.05). Higher F-FDG uptake is associated with MYCN amplification (all P < 0.05) and anatomic invasive features of tumors such as vascular encasement or adjacent organ invasion (TLG, P = 0.05). Only volumetric indices (DTV, TLDA, MTV, and TLG) significantly differed among risk groups (all P < 0.05).

CONCLUSIONS

Pretherapeutic F-DOPA and F-FDG PET provided complementary information, and both can be served for risk stratification. Volumetric indices of F-DOPA and F-FDG PET correlate more highly with risk grouping.

Neuroblastoma: MIBG Imaging and New Tracers

Neuroblastoma is an embryonic tumor of the peripheral sympathetic nervous system, and is metastatic or otherwise high risk for relapse in nearly 50% of cases, with a long-term survival of <40%. Therefore, exact staging with radiological and nuclear medicine imaging methods is crucial for finding the adequate therapeutic choice. The tumor cells express the norepinephrine transporter, which makes metaiodobenzylguanidine (MIBG), an analogue of norepinephrine, an ideal tumor-specific agent for imaging. On the contrary, MIBG imaging has several disadvantages such as limited spatial resolution, limited sensitivity in small lesions, need for two or even more acquisition sessions, and a delay between the start of the examination and result. Most of these limitations can be overcome with positron emission tomography (PET) using different radiotracers. Furthermore, for operative or biopsy planning, a combination with morphological imaging methods is indispensable. This article would discuss the therapeutic strategy for primary and follow-up diagnosis in neuroblastoma using MIBG scintigraphy and different new PET tracers as well as multimodality imaging.

123I-mIBG scintigraphy in neuroblastoma: development of a SIOPEN semi-quantitative reporting ,method by an international panel

Purpose

A robust method is required to standardise objective reporting of diagnostic ¹²³I-mIBG images in neuroblastoma. Prerequisites for an appropriate system are low inter- and intra-observer error and reproducibility across a broad disease spectrum. We present a new reporting method, developed and tested for SIOPEN by an international expert panel.

Method

Patterns of abnormal skeletal ¹²³I-mIBG uptake were defined and assigned numerical scores [0–6] based on disease extent within 12 body segments. Uptake intensity was excluded from the analysis. Data sets from 82 patients were scored independently by six experienced specialists as unblinded pairs (pre- and post-induction chemotherapy) and in random order as a blinded study. Response was defined as ≥50 % reduction in post induction score compared with baseline.

Results

In total, 1968 image sets were reviewed individually. Response rates of 88 % and 82 % were recorded for patients with baseline skeletal scores ≤23 and 24-48 respectively, compared with 44 % response in patients with skeletal scores >48 (p = 0.02). Reducing the number of segments or extension scale had a small but statistically negative impact upon the number of responses detected. Intraclass correlation coefficients [ICCs] calculated for the unblinded and blinded study were 0.95 at diagnosis and 0.98 and 0.99 post-induction chemotherapy, respectively.

Conclusions

The SIOPEN mIBG score method is reproducible across the full spectrum of disease in high risk neuroblastoma. Numerical assessment of skeletal disease extent avoids subjective evaluation of uptake intensity. This robust approach provides a reliable means with which to examine the role of 123I mIBG scintigraphy as a prognostic indicator in neuroblastoma.

Prognostic value of pretreatment FDG PET in pediatric neuroblastoma

PURPOSE

This study aimed to evaluate the prognostic value of pretreatment (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in pediatric neuroblastoma patients.

METHODS

The study included 50 pediatric neuroblastoma patients who underwent diagnostic work-up FDG PET before any treatment. The maximum standardized uptake value (SUV(max)) of the primary tumor lesion (P(max)), the SUV(max) of all the tumor lesions, including the primary tumor lesion and metastatic lesions (T(max)), and the uptake ratio of T(max) to mean SUV of normal liver tissue (T(max)/L(mean)) were calculated and tested as prognostic factors.

RESULTS

Of the 50 patients, 15 (30.0%) experienced disease progression and 21 (42.0%) died during the follow-up period. On univariate analysis, the histopathology, tumor stage, bone marrow involvement, serum levels of lactate dehydrogenase (LDH), neuron-specific enolase, and ferritin, primary tumor size, P(max), T(max), and T(max)/L(mean) were significant prognostic factors for disease progression-free survival (PFS), whereas the tumor stage, serum level of LDH, T(max), and T(max)/L(mean) were determined to be significant for predicting overall survival (OS). On multivariate analysis, the histopathology and serum level of LDH were independent prognostic factors for PFS, and only the T(max)/L(mean) was an independent prognostic factor for OS. The 2-year PFS and OS rates were over 80.0% in patients with low FDG uptake, meanwhile, patients with high FDG uptake showed the 2-year PFS of less than 30.0% and OS of less than 55.0%.

CONCLUSION

FDG PET was an independent prognostic factor for OS in neuroblastoma patients. FDG PET can provide effective information on the prognosis for neuroblastoma patients.

Right adrenal gland neuroblastoma infiltrating the liver and mimicking mesenchymal hamartoma: A case report

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The right adrenal gland neuroblastoma and infiltrated the adjacent liver substance mimicking mesenchymal hamartoma of the liver.

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The Presentation of fever of unknown origin in a case of right adrenal gland neuroblastoma is rare.

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Neuroblastoma should be considered in differential diagnosis of abdominal mass in all infants and children.

Introduction

Neuroblastoma is the most common extracranial solid pediatric malignancy. The most common site is abdomen with predominance of suprarenal medulla. Infiltration of the tumour to the liver is rare. No cases were reported in the literature about the misdiagnosis of neuroblastoma as mesenchymal hamartoma in the liver.

Presentation of case

We represent a rare case of neuroblastoma misdiagnosed as mesenchymal hamartoma in liver in a six-month-old female infant presented with fever and abdominal mass. Abdominal computed tomography (CT) revealed large cystic lesion occupying most of the right liver enchroaching upon right suprarenal region and displacing the right kidney inferior suggestive for mesenchymal hamartoma. Right adrenalectomy with en-bloc resection of the adjacent liver segments was done. Postoperative pathology revealed neuroblastoma with positive specific immunohistochemistry (IHC).

Discussion

Although neuroblastoma is the second most common pediatric abdominal malignancy with specific diagnostic modalities, a misdiagnosis of a case with neuroblastoma as mesenchymal hamartoma is rare. Histopathological diagnosis of neuroblastoma with positive IHC is essential as shown in our case.

Conclusion

We represent a rare case of neuroblastoma which arose from the right adrenal gland and infiltrated the adjacent liver substance mimicking mesenchymal hamartoma of the liver. Neuroblastoma is rarely presented with pyrexia of unknown origin. Neuroblastoma should be considered in differential diagnosis of abdominal mass in all infants and children.

Neuroblastoma: paradigm for precision medicine

Neuroblastoma (NB) is the third most common pediatric cancer. Although NB accounts for 7% of pediatric malignancies, it is responsible for more than 10% of childhood cancer-related mortality. Prognosis and treatment are determined by clinical and biological risk factors. Estimated 5-year survival rates for patients with non-high-risk and high-risk NB are more than 90% and less than 50%, respectively. Recent clinical trials have continued to reduce therapy for patients with non-high-risk NB, including the most favorable subsets who are often followed with observation approaches. In contrast, high-risk patients are treated aggressively with chemotherapy, radiation, surgery, and myeloablative and immunotherapies.

DCA promotes progression of neuroblastoma tumors in nude mice

Even in the presence of oxygen most cancer cells convert glucose to lactate via pyruvate instead of performing oxidative phosphorylation (aerobic glycolysis-Warburg effect). Thus, it has been considered to shift pyruvate - the metabolite of aerobic glycolysis - to acetylCoA by activation of pyruvate dehydrogenase (PDH). AcetylCoA will then be metabolized by oxidative phosphorylation. Therefore, the purpose of this study was to shift tumor cells from aerobic glycolysis to oxidative phosphorylation using dichloroacetate (DCA), an inhibitor of PDH-kinase. The effects of DCA were assayed in vitro in Neuro-2a (murine neuroblastoma), Kelly and SK-N-SH (human neuroblastoma) as well as SkBr3 (human breast carcinoma) cell lines. The effects of DCA on tumor development were investigated in vivo using NMRI nu/nu mice bearing subcutaneous Neuro-2a xenografts. For that purpose animals were treated continuously with DCA in the drinking water. Tumor volumes were monitored using caliper measurements and via [18F]-FDG-positron emission tomography. DCA treatment increased viability/proliferation in Neuro-2a and SkBr3 cells, but did not cause significant alterations of PDH activity. However, no significant effects of DCA could be observed in Kelly and SK-N-SH cells. Accordingly, in mice bearing Neuro-2a xenografts, DCA significantly increased tumor proliferation compared to mock-treated mice. Thus, we could demonstrate that DCA - an indicated inhibitor of tumor growth - efficiently promotes tumor growth in Neuro-2a cells in vitro and in vivo.

Clinical experience with (18)F-fluorodeoxyglucose positron emission tomography and (123)I-metaiodobenzylguanine scintigraphy in pediatric neuroblastoma: complementary roles in follow-up of patients

Purpose

To evaluate the potential utility of ¹²³I-metaiodobenzylguanine (¹²³I-MIBG) scintigraphy and ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) for the detection of primary and metastatic lesions in pediatric neuroblastoma (NBL) patients, and to determine whether ¹⁸F-FDG PET is as beneficial as ¹²³I-MIBG imaging.

Methods

We selected 8 NBL patients with significant residual mass after operation and who had paired ¹²³I-MIBG and ¹⁸F-FDG PET images that were obtained during the follow-up. We retrospectively reviewed the clinical charts and the findings of 45 paired scans.

Results

Both scans correlated relatively well with the disease status as determined by standard imaging modalities during follow-up; the overall concordance rates were 32/45 (71.1%) for primary tumor sites and 33/45 (73.3%) for bone-bone marrow (BM) metastatic sites. In detecting primary tumor sites, ¹²³I-MIBG might be superior to ¹⁸F-FDG PET. The sensitivity of ¹²³I-MIBG and ¹⁸F-FDG PET were 96.7% and 70.9%, respectively, and their specificity were 85.7% and 92.8%, respectively. ¹⁸F-FDG PET failed to detect 9 true NBL lesions in 45 follow-up scans (false negative rate, 29%) with positive ¹²³I-MIBG. For bone-BM metastatic sites, the sensitivity of ¹²³I-MIBG and ¹⁸F-FDG PET were 72.7% and 81.8%, respectively, and the specificity were 79.1% and 100%, respectively. ¹²³I-MIBG scan showed higher false positivity (20.8%) than ¹⁸F-FDG PET (0%).

Conclusion

¹²³I-MIBG is superior for delineating primary tumor sites, and ¹⁸F-FDG PET could aid in discriminating inconclusive findings on bony metastatic NBL. Both scans can be complementarily used to clearly determine discrepancies or inconclusive findings on primary or bone-BM metastatic NBL during follow-up.

Imaging the norepinephrine transporter in neuroblastoma: a comparison of [18F]-MFBG and 123I-MIBG

PURPOSE

The norepinephrine transporter (NET) is a critical regulator of catecholamine uptake in normal physiology and is expressed in neuroendocrine tumors like neuroblastoma. Although the norepinephrine analog, meta-iodobenzylguanidine (MIBG), is an established substrate for NET, (123)I/(131)I-MIBG has several clinical limitations for diagnostic imaging. In the current studies, we evaluated meta-[(18)F]-fluorobenzylguanidine ([(18)F]-MFBG) and compared it with (123)I-MIBG for imaging NET-expressing neuroblastomas.

EXPERIMENTAL DESIGN

NET expression levels in neuroblastoma cell lines were determined by Western blot and (123)I-MIBG uptake assays. Five neuroblastoma cell lines and two xenografts (SK-N-BE(2)C and LAN1) expressing different levels of NET were used for comparative in vitro and in vivo uptake studies.

RESULTS

The uptake of [(18)F]-MFBG in cells was specific and proportional to the expression level of NET. Although [(18)F]-MFBG had a 3-fold lower affinity for NET and an approximately 2-fold lower cell uptake in vitro compared with that of (123)I-MIBG, the in vivo imaging and tissue radioactivity concentration measurements demonstrated higher [(18)F]-MFBG xenograft uptake and tumor-to-normal organ ratios at 1 and 4 hours after injection. A comparison of 4 hours [(18)F]-MFBG PET (positron emission tomography) imaging with 24 hours (123)I-MIBG SPECT (single-photon emission computed tomography) imaging showed an approximately 3-fold higher tumor uptake of [(18)F]-MFBG, but slightly lower tumor-to-background ratios in mice.

CONCLUSIONS

[(18)F]-MFBG is a promising radiopharmaceutical for specifically imaging NET-expressing neuroblastomas, with fast pharmacokinetics and whole-body clearance. [(18)F]-MFBG PET imaging shows higher sensitivity, better detection of small lesions with low NET expression, allows same day scintigraphy with a shorter image acquisition time, and has the potential for lower patient radiation exposure compared with (131)I/(123)I-MIBG.

(18)F-FDG PET as a single imaging modality in pediatric neuroblastoma: comparison with abdomen CT and bone scintigraphy

OBJECTIVE

The purpose of this study was to evaluate the diagnostic performance of (18)F-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) as a single imaging agent in neuroblastoma in comparison with other imaging modalities.

METHODS

A total of 30 patients with pathologically proven neuroblastoma who underwent FDG PET for staging were enrolled. Diagnostic performance of FDG PET and abdomen CT was compared in detecting soft tissue lesions. FDG PET and bone scintigraphy (BS) were compared in bone metastases. Maximal standardized uptake value (SUVmax) of primary or recurrent lesions was calculated for quantitative analysis.

RESULTS

Tumor FDG uptake was detected in 29 of 30 patients with primary neuroblastoma. On initial FDG PET, SUVmax of primary lesions were lower in early stage (I-II) than in late stage (III-IV) (3.03 vs. 5.45, respectively, p = 0.019). FDG PET was superior to CT scan in detecting distant lymph nodes (23 vs. 18 from 23 lymph nodes). FDG PET showed higher accuracy to identify bone metastases than BS both on patient-based analyses (100 vs. 94.4 % in sensitivity, 100 vs. 77.8 % in specificity), and on lesion-based analyses (FDG PET: 203 lesions, BS: 86 lesions). Sensitivity and specificity of FDG PET to detect recurrence were 87.5 % and 93.8, respectively.

CONCLUSION

FDG PET was superior to CT in detecting distant LN metastasis and to BS in detecting skeletal metastasis in neuroblastoma. BS might be eliminated in the evaluation of neuroblastoma when FDG PET is performed.

Tumor dosimetry using [124I]m-iodobenzylguanidine microPET/CT for [131I]m-iodobenzylguanidine treatment of neuroblastoma in a murine xenograft model

PURPOSE

[(124)I]m-iodobenzylguanidine ((124)I-mIBG) provides a quantitative tool for pretherapy tumor imaging and dosimetry when performed before [(131)I]m-iodobenzylguanidine ((131)I-mIBG) targeted radionuclide therapy of neuroblastoma. (124)I (T (1/2) = 4.2 days) has a comparable half-life to that of (131)I (T (1/2) = 8.02 days) and can be imaged by positron emission tomography (PET) for accurate quantification of the radiotracer distribution. We estimated expected radiation dose in tumors from (131)I-mIBG therapy using (124)I-mIBG microPET/CT imaging data in a murine xenograft model of neuroblastoma transduced to express high levels of the human norepinephrine transporter (hNET).

PROCEDURES

In order to enhance mIBG uptake for in vivo imaging and therapy, NB 1691-luciferase (NB1691) human neuroblastoma cells were engineered to express high levels of hNET protein by lentiviral transduction (NB1691-hNET). Both NB1691 and NB1691-hNET cells were implanted subcutaneously and into renal capsules in athymic mice. (124)I-mIBG (4.2-6.5 MBq) was administered intravenously for microPET/CT imaging at 5 time points over 95 h (0.5, 3-5, 24, 48, and 93-95 h median time points). In vivo biodistribution data in normal organs, tumors, and whole-body were collected from reconstructed PET images corrected for photon attenuation using the CT-based attenuation map. Organ and tumor dosimetry were determined for (124)I-mIBG. Dose estimates for (131)I-mIBG were made, assuming the same in vivo biodistribution as (124)I-mIBG.

RESULTS

All NB1691-hNET tumors had significant uptake and retention of (124)I-mIBG, whereas unmodified NB1691 tumors did not demonstrate quantifiable mIBG uptake in vivo, despite in vitro uptake. (124)I-mIBG with microPET/CT provided an accurate three-dimensional tool for estimating the radiation dose that would be delivered with (131)I-mIBG therapy. For example, in our model system, we estimated that the administration of (131)I-mIBG in the range of 52.8-206 MBq would deliver 20 Gy to tumors.

CONCLUSIONS

The overexpression of hNET was found to be critical for (124)I-mIBG uptake and retention in vivo. The quantitative (124)I-mIBG PET/CT is a promising new tool to predict tumor radiation doses with (131)I-mIBG therapy of neuroblastoma. This methodology may be applied to tumor dosimetry of (131)I-mIBG therapy in human subjects using (124)I-mIBG pretherapy PET/CT data.

Nuclear medicine and multimodality imaging of pediatric neuroblastoma

Neuroblastoma is an embryonic tumor of the peripheral sympathetic nervous system and is metastatic or high risk for relapse in nearly 50% of cases. Therefore, exact staging with radiological and nuclear medicine imaging methods is crucial for defining the adequate therapeutic choice. Tumor cells express the norepinephrine transporter, which makes metaiodobenzylguanidine (MIBG), an analogue of norepinephrine, an ideal tumor specific agent for imaging. MIBG imaging has several disadvantages, such as limited spatial resolution, limited sensitivity in small lesions and the need for two or even more acquisition sessions. Most of these limitations can be overcome with positron emission tomography (PET) using [F-18]2-fluoro-2-deoxyglucose [FDG]. Furthermore, new tracers, such as fluorodopa or somatostatin receptor agonists, have been tested for imaging neuroblastoma recently. However, MIBG scintigraphy and PET alone are not sufficient for operative or biopsy planning. In this regard, a combination with morphological imaging is indispensable. This article will discuss strategies for primary and follow-up diagnosis in neuroblastoma using different nuclear medicine and radiological imaging methods as well as multimodality imaging.

Ten challenges in the management of neuroblastoma

Neuroblastoma is a complex disease with many contradictions and challenges. It is, by and large, a cancer of babies and preschool children, but it does occur, albeit increasingly rarely, in older children, adolescents and young adults. The prognosis is very variable, with outcome related to age, stage and molecular pathology. Neuroblastoma may behave in an almost benign way, with spontaneous regression in some infants, but the majority of older patients have high-risk disease, which is usually fatal, despite best current treatments. As a rare disease, international collaboration is essential to run clinical trials of adequate statistical power to answer important questions in a reasonable time frame. High-risk disease requires multimodality therapy including chemotherapy, surgery and radiotherapy as well as biological and immunological treatments for optimal outcomes. Innovative treatment approaches, sometimes associated with appreciable toxicity, offer hope for the future but, despite parental wishes, cannot be generally implemented without adequate assessment in clinical trials.

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.

Molecular imaging of adrenal neoplasms

The adrenal glands are complex structures from which a variety of benign and malignant tumors may arise and are a common site of metastatic disease. Several radiopharmaceuticals are used for imaging the adrenals, including I-123/I-131 metaiodobenzylguanidine (MIBG), norcholesterol derivatives, In-111 pentetreotide and Ga-68 somatostatin analogs, [F-18]fluorodeoxyglucose, [F-18]fluorodopa, [F-18]fluorodopamine, C-11 meta hydroxyephedrine, and C-11/F-18/I-123 Metomidate (MTO) or its analogs. In this review we focus on the role of these reagents in metastatic lesions, cortical neoplasms, pheochromocytoma/paraganglioma, and neuroblastoma (NB).

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.

Safety and efficacy of tandem 131I-metaiodobenzylguanidine infusions in relapsed/refractory neuroblastoma

BACKGROUND

Targeted radiotherapy with (131) I-Metaiodobenzylguanidine ((131) I-MIBG) is safe and effective therapy for patients with relapsed neuroblastoma, but anti-tumor activity is sometimes transient. The goal of this study was to determine the safety and efficacy of early (<100 days) second (131) I-MIBG treatment following an effective initial treatment.

PROCEDURES

After an initial infusion of 18 mCi/kg (131) I-MIBG, patients with tumor response or stable disease (SD), and available hematopoietic stem cell product, were eligible for additional (131) I-MIBG therapy. Residual thrombocytopenia did not preclude patients from receiving additional treatment. Subsequent treatment was administered a minimum of 6 weeks and maximum 100 days from initial infusion, and subjects could receive subsequent therapy if the same criteria were met.

RESULTS

Seventy-six heavily pretreated patients (median 4 prior chemotherapy regimens, range 1-8) with relapsed neuroblastoma were treated with (131) I-MIBG. Response rate to the first infusion was 30%, with 49% showing SD. Response rate among the 41 patients receiving a subsequent second infusion was 29%. After two treatments, 39% of patients experienced a reduction in overall disease burden. Four of five complete responses (CRs) to the initial infusion were maintained, despite all five having disease readily apparent on immediate post-second treatment (131) I-MIBG scanning. Hematologic toxicity was managed with early PBSC support after the second therapy (median: 15 days).

CONCLUSIONS

Early second (131) I-MIBG safely reduces disease burden in patients with relapsed neuroblastoma. Patients with CR by conventional (123) I-MIBG scintigraphy may have substantial disease burden apparent on high-dose (131) I-MIBG scintigraphy, supporting consolidation with subsequent (131) I-MIBG therapy in cases of apparent complete remission. Pediatr Blood Cancer 2011; 57: 1124-1129. © 2011 Wiley Periodicals, Inc.

Comparison of 18F-dopa PET/CT and 123I-MIBG scintigraphy in stage 3 and 4 neuroblastoma: a pilot study

PURPOSE

(18)F-Dopa positron emission tomography (PET)/CT has proved a valuable tool for the assessment of neuroendocrine tumours. So far no data are available on (18)F-dopa utilization in neuroblastoma (NB). Our aim was to evaluate the role of (18)F-dopa PET/CT in NB and compare its diagnostic value with that of (123)I-metaiodobenzylguanidine (MIBG) scintigraphy in patients affected by stage 3-4 NB.

METHODS

We prospectively evaluated 28 paired (123)I-MIBG and (18)F-dopa PET/CT scans in 19 patients: 4 at the time of the NB diagnosis and 15 when NB relapse was suspected. For both imaging modalities we performed a scan-based and a lesion-based analysis and calculated sensitivity, specificity and accuracy. The standard of reference was based on clinical, imaging and histological data.

RESULTS

NB localizations were confirmed in 17 of 19 patients. (18)F-Dopa PET/CT and (123)I-MIBG scintigraphy properly detected disease in 16 (94%) and 11 (65%), respectively. On scan-based analysis, (18)F-dopa PET/CT showed a sensitivity and accuracy of 95 and 96%, respectively, while (123)I-MIBG scanning showed a sensitivity and accuracy of 68 and 64%, respectively (p < 0.05). No significant difference in terms of specificity was found. In 9 of 28 paired scans (32%) PET/CT results influenced the patient management. We identified 156 NB localizations, 141 of which were correctly detected by (18)F-dopa PET/CT and 88 by MIBG. On lesion-based analysis, (18)F-dopa PET/CT showed a sensitivity and accuracy of 90% whereas (123)I-MIBG scintigraphy showed a sensitivity and accuracy of 56 and 57%, respectively (p < 0.001). No significant difference in terms of specificity was found.

CONCLUSION

In our NB population (18)F-dopa PET/CT displayed higher overall accuracy than (123)I-MIBG scintigraphy. Consequently, we suggest (18)F-dopa PET/CT as a new opportunity for NB assessment.

Clinical significance of 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography for the assessment of 131I-metaiodobenzylguanidine therapy in malignant phaeochromocytoma

PURPOSE

The aim of this study was to evaluate the significance of 2-[18F]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) in the assessment of the therapeutic response to 131I-metaiodobenzylguanidine (MIBG) in malignant phaeochromocytoma.

METHODS

We reviewed the records of 11 patients (7 men and 4 women) with malignant phaeochromocytoma who underwent 131I-MIBG therapy (100-200 mCi). 18F-FDG PET and serum catecholamine assays were performed 3 months before and after the first dose of 131I-MIBG. FDG uptake was evaluated in the observed lesions using the maximum standardised uptake value (SUVmax). The average SUVmax of all lesions (ASUV) was calculated. If more than five lesions were identified, the average SUVmax of the five highest SUVmax (ASUV5) was calculated. The ratio of pre- and post-therapy values was calculated for the highest SUVmax (rMSUV), ASUV (rASUV), ASUV5 (rASUV5), CT diameter (rCT) and serum catecholamine (rCA). Responder (R) and non-responder (NR) groups were defined after a clinical follow-up of at least 6 months according to changes in symptoms, CT, magnetic resonance imaging (MRI) and 123I-MIBG scan.

RESULTS

Post-therapy evaluation revealed five R and six NR patients. The size of the target lesions was not significantly different before and after therapy (p>0.05). However, ASUV and ASUV5 were significantly lower in the R group (rASUV 0.64±0.18, rASUV5 0.68±0.17) compared to the NR group (rASUV 1.40±0.54, rASUV5 1.37±0.61) (p<0.05).

CONCLUSION

18F-FDG PET can be potentially used to evaluate the response of malignant phaeochromocytoma to 131I-MIBG therapy.

¹²³I-MIBG scintigraphy/SPECT versus ¹⁸F-FDG PET in paediatric neuroblastoma

PURPOSE

To analyse different uptake patterns in (123)I-MIBG scintigraphy/SPECT imaging and (18)F-FDG PET in paediatric neuroblastoma patients.

METHODS

We compared 23 (123)I-MIBG scintigraphy scans and 23 (18)F-FDG PET scans (mean interval 10 days) in 19 patients with a suspected neuroblastic tumour (16 neuroblastoma, 1 ganglioneuroblastoma, 1 ganglioneuroma and 1 opsomyoclonus syndrome). SPECT images of the abdomen or other tumour-affected regions were available in all patients. Indications for (18)F-FDG PET were a (123)I-MIBG-negative tumour, a discrepancy in (123)I-MIBG uptake compared to the morphological imaging or imaging results inconsistent with clinical findings. A lesion was found by (123)I-MIBG scintigraphy and/or (18)F-FDG PET and/or morphological imaging.

RESULTS

A total of 58 suspicious lesions (mean lesion diameter 3.8 cm) were evaluated and 18 were confirmed by histology and 40 by clinical follow-up. The sensitivities of (123)I-MIBG scintigraphy and (18)F-FDG PET were 50% and 78% and the specificities were 75% and 92%, respectively. False-positive results (three (123)I-MIBG scintigraphy, one (18)F-FDG PET) were due to physiological uptake or posttherapy changes. False-negative results (23 (123)I-MIBG scintigraphy, 10 (18)F-FDG PET) were due to low uptake and small lesion size. Combined (123)I-MIBG scintigraphy/(18)F-FDG PET imaging showed the highest sensitivity of 85%. In 34 lesions the (123)I-MIBG scintigraphy and morphological imaging findings were discrepant. (18)F-FDG PET correctly identified 32 of the discrepant findings. Two bone/bone marrow metastases were missed by (18)F-FDG PET.

CONCLUSION

(123)I-MIBG scintigraphy and (18)F-FDG PET showed noticeable differences in their uptake patterns. (18)F-FDG PET was more sensitive and specific for the detection of neuroblastoma lesions. Our findings suggest that a (18)F-FDG PET scan may be useful in the event of discrepant or inconclusive findings on (123)I-MIBG scintigraphy/SPECT and morphological imaging.

Guidelines for imaging and staging of neuroblastic tumors: consensus report from the International Neuroblastoma Risk Group Project

Neuroblastoma is an enigmatic disease entity; some tumors disappear spontaneously without any therapy, while others progress with a fatal outcome despite the implementation of maximal modern therapy. However, strong prognostic factors can accurately predict whether children have "good" or "bad" disease at diagnosis, and the clinical stage is currently the most significant and clinically relevant prognostic factor. Therefore, for an individual patient, proper staging is of paramount importance for risk assessment and selection of optimal treatment. In 2009, the International Neuroblastoma Risk Group (INRG) Project proposed a new staging system designed for tumor staging before any treatment, including surgery. Compared with the focus of the International Neuroblastoma Staging System, which is currently the most used, the focus has now shifted from surgicopathologic findings to imaging findings. The new INRG Staging System includes two stages of localized disease, which are dependent on whether image-defined risk factors (IDRFs) are or are not present. IDRFs are features detected with imaging at the time of diagnosis. The present consensus report was written by the INRG Imaging Committee to optimize imaging and staging and reduce interobserver variability. The rationales for using imaging methods (ultrasonography, magnetic resonance imaging, computed tomography, and scintigraphy), as well as technical guidelines, are described. Definitions of the terms recommended for assessing IDRFs are provided with examples. It is anticipated that the use of standardized nomenclature will contribute substantially to more uniform staging and thereby facilitate comparisons of clinical trials conducted in different parts of the world.

What is the relationship between ¹⁸F-FDG aortic aneurysm uptake on PET/CT and future growth rate?

PURPOSE

In this study we investigate the relationship between (18)F-fluorodeoxyglucose (FDG) metabolism and future aneurysm expansion measured by serial duplex ultrasound. Current screening programmes are increasing the identification of patients with abdominal aortic aneurysm (AAA). The management of these patients remains challenging and methods of risk stratification are sought.

METHODS

Thirty-four consecutive patients [31 men, 3 women, median age 75 years, interquartile range (IQR) 71-78] with aortic aneurysms under routine surveillance with serial ultrasound were prospectively recruited for (18)F-FDG positron emission tomography (PET)/CT. A whole vessel type analysis was performed measuring the highest aortic wall (18)F-FDG uptake (standardized uptake value or SUV(max)), and target to background ratio (TBR) for each axial image and median SUV(max) and TBR value were calculated. Institutional Review Board permission and informed patient consent were obtained.

RESULTS

Nine patients failed to undergo 12-month follow-up study (deceased n = 2, withdrew n = 1, failed to attend ultrasound scan n = 5, emergency aneurysm repair n = 1) leaving 25 patients for analysis. The median whole vessel SUV(max) was 1.70 (IQR 1.45-2.08). The median whole vessel TBR was 1.15 (IQR 1.00-1.40). The median aneurysm expansion at 12 months was 2.0 mm (IQR 0.5-5.0). The correlation (r) between (18)F-FDG SUV(max) and ultrasound expansion at 1 year was -0.501 (p = 0.011).

CONCLUSION

The preliminary findings from this observational longitudinal pilot study suggest that there is an inverse trend between (18)F-FDG uptake on PET and future AAA expansion. Aortic aneurysms with lower metabolic activity may therefore be more likely to expand.