Sentinel lymph node biopsy in head and neck rhabdomyosarcoma.

Head and neck rhabdomyosarcoma lymph node staging is challenging due to varied patterns of lymphatic drainage and the suboptimal predictive value of available imaging modalities. Furthermore, regional relapse rates are unacceptably high, and the toxicity of empiric radiation is undesirable in the pediatric and young adult population. In an attempt to improve locoregional control without excess morbidity, we have adopted routine sentinel lymph node biopsy in head and neck rhabdomyosarcoma, which is safe and feasible in pediatric patients. Of six procedures reported here, pathologic findings led to intensification of regional and/or systemic therapy in two patients.

Differentiated Thyroid Cancer in the Pediatric/Adolescent Population: Evolution of Treatment.

Differentiated thyroid cancer (DTC) is the most common cancer in adolescents and young adults. In 2015, the American Thyroid Association published guidelines for management of pediatric DTC. We report our institutional experience and highlight changing practices and new opportunities. A retrospective analysis of all patients diagnosed with DTC from 2001 to 2016 was performed. Among 59 eligible patients, 31 (53%), 15 (25%), and 13 (22%) had low-risk, intermediate-risk, and high-risk disease, respectively. Half (15/31) of low-risk and all intermediate-risk/high-risk patients received radioactive iodine (I-131) ablation. For low-risk patients, average I-131 dose decreased from 80 to 42.05 mCi, and the percentage of patients who received I-131 decreased over time. Eleven of 16 patients with tumor genomic data were found to have somatic targetable (n=6) or germline (n=5) mutations. Persistent/recurrent disease was only present in high-risk (n=8) and intermediate-risk (n=1) patients. Two patients with iodine-refractory disease received trametinib to enhance radioiodine uptake. All patients were alive at follow-up (median, 5 y; range, 1 to 15 y). Coincident with the recent American Thyroid Association guidelines, the use of I-131 in low-risk patients has decreased over time in our practice. Tumor sequencing and cancer genetic evaluation may help redefine opportunities for treatment of high-risk patients and family counseling.

Validation of the mIBG skeletal SIOPEN scoring method in two independent high-risk neuroblastoma populations: the SIOPEN/HR-NBL1 and COG-A3973 trials.

BACKGROUND: Validation of the prognostic value of the SIOPEN mIBG skeletal scoring system in two independent stage 4, mIBG avid, high-risk neuroblastoma populations. RESULTS: The semi-quantitative SIOPEN score evaluates skeletal meta-iodobenzylguanidine (mIBG) uptake on a 0-6 scale in 12 anatomical regions. Evaluable mIBG scans from 216 COG-A3973 and 341 SIOPEN/HR-NBL1 trial patients were reviewed pre- and post-induction chemotherapy. The prognostic value of skeletal scores for 5-year event free survival (5 yr.-EFS) was tested in the source and validation cohorts. At diagnosis, both cohorts showed a gradual non-linear increase in risk with cumulative scores. Several approaches were explored to test the relationship between score and EFS. Ultimately, a cutoff score of ≤3 was the most useful predictor across trials. A SIOPEN score ≤ 3 pre-induction was found in 15% SIOPEN patients and in 22% of COG patients and increased post-induction to 60% in SIOPEN patients and to 73% in COG patients. Baseline 5 yr.-EFS rates in the SIOPEN/HR-NBL1 cohort for scores ≤3 were 47% ± 7% versus 26% ± 3% for higher scores at diagnosis (p < 0.007) and 36% ± 4% versus 14% ± 4% (p < 0.001) for scores obtained post-induction. The COG-A3973 showed 5 yr.-EFS rates for scores ≤3 of 51% ± 7% versus 34% ± 4% for higher scores (p < 0.001) at diagnosis and 43% ± 5% versus 16% ± 6% (p = 0.004) for post-induction scores. Hazard ratios (HR) significantly favoured patients with scores ≤3 after adjustment for age and MYCN-amplification. Optimal outcomes were recorded in patients who achieved complete skeletal response. CONCLUSIONS: Validation in two independent cohorts confirms the prognostic value of the SIOPEN skeletal score. In particular, patients with an absolute SIOPEN score > 3 after induction have very poor outcomes and should be considered for alternative therapeutic strategies.

Detection of lymph node metastases in pediatric and adolescent/young adult sarcoma: Sentinel lymph node biopsy versus fludeoxyglucose positron emission tomography imaging-A prospective trial.

BACKGROUND: Lymph node metastases are an important cause of treatment failure for pediatric and adolescent/young adult (AYA) sarcoma patients. Nodal sampling is recommended for certain sarcoma subtypes that have a predilection for lymphatic spread. Sentinel lymph node biopsy (SLNB) may improve the diagnostic yield of nodal sampling, particularly when single-photon emission computed tomography/computed tomography (SPECT-CT) is used to facilitate anatomic localization. Functional imaging with positron emission tomography/computed tomography (PET-CT) is increasingly used for sarcoma staging and is a less invasive alternative to SLNB. To assess the utility of these 2 staging methods, this study prospectively compared SLNB plus SPECT-CT with PET-CT for the identification of nodal metastases in pediatric and AYA patients. METHODS: Twenty-eight pediatric and AYA sarcoma patients underwent SLNB with SPECT-CT. The histological findings of the excised lymph nodes were then correlated with preoperative PET-CT imaging. RESULTS: A median of 2.4 sentinel nodes were sampled per patient. No wound infections or chronic lymphedema occurred. SLNB identified tumors in 7 of the 28 patients (25%), including 3 patients who had normal PET-CT imaging of the nodal basin. In contrast, PET-CT demonstrated hypermetabolic regional nodes in 14 patients, and this resulted in a positive predictive value of only 29%. The sensitivity and specificity of PET-CT for detecting histologically confirmed nodal metastases were only 57% and 52%, respectively. CONCLUSIONS: SLNB can safely guide the rational selection of nodes for biopsy in pediatric and AYA sarcoma patients and can identify therapy-changing nodal disease not appreciated with PET-CT. Cancer 2017;155-160. © 2016 American Cancer Society.

FDG PET/CT appearance of local osteosarcoma recurrences in pediatric patients.

BACKGROUND: Osteosarcoma is the most common pediatric malignant bone tumor, frequently surgically managed with limb salvage rather than amputation. Local recurrences are seen in up to 9% of osteosarcoma patients, with CT and MRI imaging often limited by metal artifacts. OBJECTIVE: To describe the [F-18]2-fluoro-2-deoxyglucose (FDG) PET/CT appearance of local osteosarcoma recurrences with correlation to findings on other imaging modalities. MATERIALS AND METHODS: A retrospective review of pediatric osteosarcoma patients imaged with FDG PET/CT was performed in patients with pathologically proven local recurrences. FDG PET/CT findings were reviewed and correlated with available comparison imaging studies. RESULTS: Ten local osteosarcoma recurrences in eight pediatric osteosarcoma patients were imaged with FDG PET/CT. All eight patients had a local recurrence after limb salvage; two patients had a second local recurrence after amputation. All local recurrences were seen with FDG PET/CT, demonstrating solid (n=5) or peripheral/nodular (n=5) FDG uptake patterns. Maximum standard uptake values (SUVs) ranged from 3.0 to 15.7. In five recurrences imaged with FDG PET/CT and MRI, MRI was limited or nondiagnostic in three. In four recurrences imaged with FDG PET/CT and bone scan, the bone scan was negative in three. CONCLUSION: Local osteosarcoma recurrences are well visualized by FDG PET/CT, demonstrating either solid or peripheral/nodular FDG uptake with a wide range of maximum SUVs. FDG PET/CT demonstrates the full extent of local recurrences, while MRI can be limited by artifact from metallic hardware. PET/CT appears to be more sensitive than bone scan in detecting local osteosarcoma recurrences.

MIBG in Neuroblastoma Diagnostic Imaging and Therapy.

Neuroblastoma is a common malignancy observed in infants and young children. It has a varied prognosis, ranging from spontaneous regression to aggressive metastatic tumors with fatal outcomes despite multimodality therapy. Patients are divided into risk groups on the basis of age, stage, and biologic tumor factors. Multiple clinical and imaging tests are needed for accurate patient assessment. Iodine 123 ((123)I) metaiodobenzylguanidine (MIBG) is the first-line functional imaging agent used in neuroblastoma imaging. MIBG uptake is seen in 90% of neuroblastomas, identifying both the primary tumor and sites of metastatic disease. The addition of single photon emission computed tomography (SPECT) and SPECT/computed tomography to (123)I-MIBG planar images can improve identification and characterization of sites of uptake. During scan interpretation, use of MIBG semiquantitative scoring systems improves description of disease extent and distribution and may be helpful in defining prognosis. Therapeutic use of MIBG labeled with iodine 131 ((131)I) is being investigated as part of research trials, both as a single agent and in conjunction with other therapies. (131)I-MIBG therapy has been studied in patients with newly diagnosed neuroblastoma and those with relapsed disease. Development and implementation of an institutional (131)I-MIBG therapy research program requires extensive preparation with a focus on radiation protection.

Prospective detection of cortical dysplasia on clinical MRI in pediatric intractable epilepsy.

BACKGROUND: Cortical dysplasia is the most common cause of pediatric refractory epilepsy. MRI detection of epileptogenic lesion is associated with good postsurgical outcome. Additional electrophysiological information is suggested to be helpful in localization of cortical dysplasia. Educational measures were taken to increase the awareness of cortical dysplasia at our institution in the context of a recent International League Against Epilepsy (ILAE 2011) classification of cortical dysplasia. OBJECTIVE: To determine changes in the rate of prospective identification of cortical dysplasia on an initial radiology report and also evaluate the benefit of MRI review as part of a multidisciplinary epilepsy conference in identifying previously overlooked MRI findings. MATERIALS AND METHODS: We retrospectively evaluated surgically treated children with refractory epilepsy from 2007 to 2014 with cortical dysplasia on histopathology. We analyzed the initial radiology report, preoperative MRI interpretation at multidisciplinary epilepsy conference and subsequent retrospective MRI review with knowledge of the resection site. We recorded additional electrophysiological data and the presence of lobar concordance with the MRI findings. RESULTS: Of 78 children (44 MRI lesional) evaluated, 18 had initially overlooked MRI findings. Comparing 2007-2010 to 2011-2014, there was improvement in the rate of overlooked findings on the initial radiology report (54% vs. 13% of lesional cases, respectively; P = 0.008). The majority (72%) were identified at a multidisciplinary conference with lobar concordance of findings with at least one additional electrophysiological investigation in 89%. CONCLUSION: Awareness of current classification schemes of cortical dysplasia and image review in the context of a multidisciplinary conference can lead to improved MRI detection of cortical dysplasia in children.

Spondylolysis and Beyond: Value of SPECT/CT in Evaluation of Low Back Pain in Children and Young Adults.

Single photon emission computed tomography (SPECT)/computed tomography (CT) is ideally suited for assessment of low back pain in children and young adults. Spondylolysis is one of the most common structural causes of low back pain and is readily identified and characterized in terms of its chronicity and likelihood to heal. The value of SPECT/CT extends to identification and characterization of other causes of low back pain, including abnormalities of the posterior elements, developing vertebral endplate, transverse processes, and sacrum and sacroiliac joint. Some of the disease processes that are identifiable at SPECT/CT are similar to those that occur in adults (eg, facet hypertrophy) but may be accelerated in young patients by high-level athletic activities. Other processes (eg, limbus vertebrae) are more unique to children, related to injury of the developing spine. The authors review the spectrum of pars interarticularis abnormalities with emphasis on the imaging features of causes of pediatric low back pain other than spondylolysis.

[F-18]2-fluoro-2-deoxyglucose (FDG) positron emission tomography after limb salvage surgery: post-surgical appearance, attenuation correction and local complications.

BACKGROUND: Metal endoprostheses and internal fixation devices cause significant artifacts on CT after limb salvage surgery; positron emission tomography (PET) images should be evaluated for artifacts. OBJECTIVE: (1) To describe [F-18]2-fluoro-2-deoxyglucose (FDG) PET uptake patterns after limb salvage surgery. (2) To determine whether metal endoprostheses and fixation hardware cause significant artifacts on CT attenuation-corrected PET that interfere with diagnostic use of PET/CT after limb salvage surgery. MATERIALS AND METHODS: We reviewed 92 studies from 18 patients ages 5-21 years. Diagnoses were osteogenic sarcoma in 14, Ewing sarcoma in 3, and malignant peripheral nerve sheath tumor originating in bone in 1. Nine patients had distal femur/knee endoprostheses, five had lower-extremity bone allografts secured by large metal plates and four had upper-extremity limb salvage procedures. Maximum standardized uptake value was calculated at lower-extremity soft-tissue-endoprosthesis interfaces. In 15 patients with PET/CT imaging, the first PET/CT scan after limb salvage surgery was reviewed for metal artifacts on CT images and for artifacts at locations on PET corresponding to the CT metal artifacts. RESULTS: Increased FDG uptake was consistently present at soft-tissue interfaces with endoprostheses, allografts and internal fixation devices, with little or no FDG uptake at cemented endoprosthesis-bone interfaces. Maximum standardized uptake value at margins of femur/knee endoprostheses ranged from 1.4 to 5.7. In four patients with distal femur/knee endoprostheses, minimal artifact was noted on attenuation-corrected PET images, but image interpretation was not affected. In the other 11 patients who had CT attenuation correction, we detected no artifacts caused by the attenuation correction. CONCLUSION: CT attenuation correction did not cause artifacts that affected interpretation of attenuation-corrected PET images.

Selective CT for PET/CT: dose reduction in Langerhans cell histiocytosis.

BACKGROUND: In Langerhans cell histiocytosis (LCH), FDG PET demonstrates active disease in bone. Other imaging modalities show the effects of bone destruction by LCH. OBJECTIVE: To evaluate a selective CT method for reducing effective dose from FDG PET/CT in LCH, using whole-body modified attenuation correction CT at extremely low exposure settings, with repeat selective limited-volume CT at typical localization settings. MATERIALS AND METHODS: Fifty-one PET/CT scans were performed in 23 LCH patients, median patient age 8.5 years (range: 1-25 years). Thirty-four were performed with modified attenuation correction CT settings, with bed positions (excluding head and neck) repeated at localization CT settings in regions with abnormal or difficult to interpret PET findings. RESULTS: Of 34 modified attenuation correction PET/CT scans, 10 required repeat localization CT of 1 to 3 bed positions (total: 17 bed positions). Lytic bone lesions were easily recognized at modified attenuation correction settings. Calculated average effective dose for the 34 whole-body CT scans at modified attenuation correction settings was 1.65 mSv. Average effective dose per patient for repeat imaging of 17 bed positions at localization settings was 1.19 mSv. Average total effective dose from CT for all 34 scans performed at the modified attenuation correction CT settings, including the 10 repeat localization CT scans, was 2.0 mSv. High-quality PET scans were consistently obtained with reduced FDG-administered activities of 3.7 MBq/kg (0.10 mCi/kg). In active LCH, abnormal FDG uptake was seen in all lytic bone lesions ≥9 mm, including cranial vault lesions. CONCLUSION: Substantial reduction in effective dose is possible using selective CT techniques for FDG PET/CT.

Radiation doses for pediatric nuclear medicine studies: comparing the North American consensus guidelines and the pediatric dosage card of the European Association of Nuclear Medicine.

BACKGROUND: Estimated radiation dose is important for assessing and communicating the risks and benefits of pediatric nuclear medicine studies. Radiation dose depends on the radiopharmaceutical, the administered activity, and patient factors such as age and size. Most radiation dose estimates for pediatric nuclear medicine have not been based on administered activities of radiopharmaceuticals recommended by established practice guidelines. The dosage card of the European Association of Nuclear Medicine (EANM) and the North American consensus guidelines each provide recommendations of administered activities of radiopharmaceuticals in children, but there are substantial differences between these two guidelines. OBJECTIVE: For 12 commonly performed pediatric nuclear medicine studies, two established pediatric radiopharmaceutical administration guidelines were used to calculate updated radiation dose estimates and to compare the radiation exposure resulting from the recommendations of each of the guidelines. MATERIALS AND METHODS: Estimated radiation doses were calculated for 12 common procedures in pediatric nuclear medicine using administered activities recommended by the dosage card of the EANM (version 1.5.2008) and the 2010 North American consensus guidelines for radiopharmaceutical administered activities in pediatrics. Based on standard models and nominal age-based weights, radiation dose was estimated for typical patients at ages 1, 5, 10 and 15 years and adult. The resulting effective doses were compared, with differences greater than 20% considered significant. RESULTS: Following either the EANM dosage card or the 2010 North American guidelines, the highest effective doses occur with radiopharmaceuticals labeled with fluorine-18 and iodine-123. In 24% of cases, following the North American consensus guidelines would result in a substantially higher radiation dose. The guidelines of the EANM dosage card would lead to a substantially higher radiation dose in 39% of all cases, and in 62% of cases in which patients were age 5 years or younger. CONCLUSION: For 12 commonly performed pediatric nuclear medicine studies, updated radiation dose estimates can guide efforts to reduce radiation exposure and provide current information for discussing radiation exposure and risk with referring physicians, patients and families. There can be substantial differences in radiation exposure for the same procedure, depending upon which of these two guidelines is followed. This discordance identifies opportunities for harmonization of the guidelines, which may lead to further reduction in nuclear medicine radiation doses in children.

Optimizing the interval between G-CSF therapy and F-18 FDG PET imaging in children and young adults receiving chemotherapy for sarcoma.

BACKGROUND: Granulocyte colony-stimulating factors (G-CSF) speed recovery from chemotherapy-induced myelosuppression but the marrow stimulation they cause can interfere with interpretation of F-18 fluorodeoxyglucose positron emission tomography (F-18 FDG PET) exams. OBJECTIVE: To assess the frequency of interfering G-CSF-induced bone marrow activity on FDG PET imaging in children and young adults with Ewing sarcoma and rhabdomyosarcoma and to define an interval between G-CSF administration and FDG PET imaging that limits marrow interference. MATERIALS AND METHODS: Blinded, retrospective review of FDG PET exams performed in patients treated with long-acting G-CSF as part of their chemotherapeutic regimen. Exams were subjectively scored by two reviewers (R1 and R2) who assessed the level of marrow uptake of FDG and measured standardized uptake values in the marrow, liver, spleen and blood pool. FDG PET findings were correlated with time since G-CSF administration and with blood cell counts. RESULTS: Thirty-eight FDG PET exams performed in 17 patients were reviewed with 47.4% (18/38) of exams having marrow uptake of FDG sufficient to interfere with image interpretation. Primary predictors of marrow uptake of FDG were patient age (P=0.0037) and time since G-CSF exposure (P=0.0028 for subjective marrow uptake of FDG, P=0.008 [R1] and P=0.004 [R2] for measured maximum standardized uptake value (SUVmax)). The median interval between G-CSF administration and PET imaging in cases with marrow activity considered normal or not likely to interfere was 19.5 days (range: 7-55 days). CONCLUSION: In pediatric and young adult patients with Ewing sarcoma and rhabdomyosarcoma, an interval of 20 days between administration of the long-acting form of G-CSF and FDG PET imaging should limit interference by stimulated marrow.

Altered FDG uptake patterns in pediatric lymphoblastic lymphoma patients receiving induction chemotherapy that includes very high dose corticosteroids.

BACKGROUND: Altered FDG uptake patterns were noted in certain lymphoblastic lymphoma patients during therapy. OBJECTIVE: To describe these altered FDG uptake patterns and their relationship to chemotherapy. MATERIALS AND METHODS: Thirty-five FDG PET or PET/CT scans obtained in 11 children with lymphoblastic lymphoma were retrospectively reviewed. FDG uptake patterns were recorded. SUV measurements were performed in liver and facial soft tissues. Results were correlated with induction chemotherapy regimens. RESULTS: Six of the children had transiently altered FDG uptake with increased uptake in the superficial soft tissues, most notably involving the face. Altered uptake was noted approximately 1 month after initiation of chemotherapy and subsequently resolved. Hepatic uptake was transiently reduced on the 1-month scan in all six children with increased facial uptake. No significant FDG uptake in lymphoma was seen on five of six scans with altered uptake; however, two of these five affected children had FDG uptake in lymphoma on the next follow-up examination. Blood glucose levels in the affected children were in the normal range. All six children with altered FDG uptake received the same induction chemotherapy regimen, which included very high doses of corticosteroids. CONCLUSIONS: Children with lymphoblastic lymphoma on induction chemotherapy protocols including very high doses of corticosteroids transiently demonstrated altered FDG uptake patterns, including increased superficial facial uptake and reduced hepatic uptake. The facial uptake is probably the FDG PET equivalent of Cushingoid facies. Caution in interpreting scans with this altered FDG uptake pattern is suggested, as uptake at sites of lymphomatous involvement may potentially be affected.

Use of sentinel node biopsy for staging parameningeal rhabdomyosarcoma.

Identification of nodal involvement is important for treatment planning in patients with rhabdomyosarcoma, and is facilitated by sentinel node biopsy. Although it is employed primarily for extremity tumors, we report using sentinel node biopsy in a patient with parameningeal rhabdomyosarcoma arising in the ethmoid sinus. Lymphoscintigraphy with single photon emission computed tomography following injection of tracer at the tumor site helped identify contralateral cervical node involvement not previously recognized by physical exam, cross sectional imaging, or other functional imaging. This case demonstrates how information from sentinel node identification and biopsy can change therapy recommendations in patients with parameningeal rhabdomyosarcoma.

A welcome surprise: nodular fasciitis presenting as soft tissue sarcoma.

A 15-year-old boy presented with a growing mass on the anterior chest wall. History, clinical examination, and preoperative imaging studies were consistent with soft tissue sarcoma. He underwent open biopsy, and the intraoperative pathology diagnosis of nodular fasciitis resulted in performance of a lesional excision, rather than a potentially morbid wide resection. Nodular fasciitis is a rare but important soft tissue lesion, which can be easily confused with sarcoma. The possibility of benign etiologies for soft tissue masses should be considered when planning surgical options, even when preoperative imaging studies suggest more aggressive lesions.

SPECT/CT imaging in children with papillary thyroid carcinoma.

BACKGROUND: SPECT/CT improves localization of single photon-emitting radiopharmaceuticals. OBJECTIVE: To determine the utility of SPECT/CT in children with papillary thyroid carcinoma. MATERIALS AND METHODS: 20 SPECT/CT and planar studies were reviewed in 13 children with papillary thyroid carcinoma after total thyroidectomy. Seven studies used I-123 and 13 used I-131, after elevating TSH by T4 deprivation or intramuscular thyrotropin alfa. Eight children had one study and five children had two to four studies. Studies were performed at initial post-total thyroidectomy evaluation, follow-up and after I-131 treatment doses. SPECT/CT was performed with a diagnostic-quality CT unit in 13 studies and a localization-only CT unit in 7. Stimulated thyroglobulin was measured (except in 2 cases with anti-thyroglobulin antibodies). RESULTS: In 13 studies, neck activity was present but poorly localized on planar imaging; all foci of uptake were precisely localized by SPECT/CT. Two additional foci of neck uptake were found on SPECT/CT. SPECT/CT differentiated high neck uptake from facial activity. In six studies (four children), neck uptake was identified as benign by SPECT/CT (three thyroglossal duct remnants, one skin contamination, two by precise anatomical CT localization). In two children, SPECT/CT supported a decision not to treat with I-131. When SPECT/CT was unable to identify focal uptake as benign, stimulated thyroglobulin measurements were valuable. In three of 13 studies with neck uptake, SPECT/CT provided no useful additional information. CONCLUSION: SPECT/CT precisely localizes neck iodine uptake. In small numbers of patients, treatment is affected. SPECT/CT should be used when available in thyroid carcinoma patients.

FDG positron emission tomography/computed tomography studies of Wilms' tumor.

PURPOSE: The purpose of this analysis was to evaluate the utility of FDG PET/CT scanning in patients with Wilms' tumors. METHODS: A total of 58 scans were performed in 27 patients (14 male, 13 female; ages: 1.9-23 years, median: 7 years) with proven Wilms' tumor. Twenty-six patients (56 scans) were studied at the time of suspected relapse, progressive disease, persistent disease, or for monitoring of therapy. RESULTS: In the 27 patients with Wilms' tumor, 34 scans showed areas of abnormal uptake consistent with metabolically active tumors. Of the patients, 8 (24 scans) had pulmonary metastases larger than 10 mm in diameter, 10 (12 scans) had hepatic metastases, 11 (11 scans) had regional nodal involvement, 3 (3 scans) had bone metastases, 1 (1 scan) had chest wall involvement, 2 (2 scans) had pancreatic metastasis, and 5 (5 scans) had abdominal and pelvic soft tissue involvement. Two of eight patients with lung metastases had variable uptakes. Lung lesions 10 mm or smaller were not consistently visualized on PET scans. One patient with a liver metastasis showed no uptake on PET scan after treatment (size decreased from 45 to 15 mm). CONCLUSION: Most Wilms' tumors concentrate FDG. However, small pulmonary metastases may be better visualized with CT. FDG PET/CT appears useful for defining the extent of involvement and assessing the response to treatment.

123I-MIBG scintigraphy and 18F-FDG PET in neuroblastoma.

UNLABELLED: The purpose of this study was to compare the diagnostic utility of (123)I-metaiodobenzylguanidine ((123)I-MIBG) scintigraphy and (18)F-FDG PET in neuroblastoma. METHODS: A total of 113 paired (123)I-MIBG and (18)F-FDG PET scans in 60 patients with neuroblastoma were retrospectively reviewed. Paired scans were acquired within 14 days of each other. RESULTS: For stage 1 and 2 neuroblastoma (13 scans, 10 patients), (18)F-FDG depicted more extensive primary or residual neuroblastoma in 9 of 13 scans. (123)I-MIBG and (18)F-FDG showed equal numbers of lesions in 1 of 13 scans, and 3 of 13 scan results were normal. For stage 3 neuroblastoma (15 scans, 10 patients), (123)I-MIBG depicted more extensive primary neuroblastoma or local or regional metastases in 5 of 15 scans. (18)F-FDG depicted more extensive primary neuroblastoma or local or regional metastases in 4 of 15 scans. (123)I-MIBG and (18)F-FDG were equal in 2 of 15 scans, and 4 of 15 scan results were normal. For stage 4 neuroblastoma (85 scans, 40 patients), (123)I-MIBG depicted more neuroblastoma sites in 44 of 85 scans. (18)F-FDG depicted more neuroblastoma sites in 11 of 85 scans. (123)I-MIBG and (18)F-FDG were equivalent or complementary in 13 of 85 scans, and 17 of 85 scan results were normal. CONCLUSION: (18)F-FDG is superior in depicting stage 1 and 2 neuroblastoma, although (123)I-MIBG may be needed to exclude higher-stage disease. (18)F-FDG also provides important information for patients with tumors that weakly accumulate (123)I-MIBG and at major decision points during therapy (i.e., before stem cell transplantation or before surgery). (18)F-FDG can also better delineate disease extent in the chest, abdomen, and pelvis. (123)I-MIBG is overall superior in the evaluation of stage 4 neuroblastoma, especially during initial chemotherapy, primarily because of the better detection of bone or marrow metastases.

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.

PET/CT and SPECT/CT dosimetry in children: the challenge to the pediatric imager.

Both positron emission tomography (PET) and computed tomography (CT) contribute significantly to the effective dose from PET/CT imaging. For PET imaging, the effective dose is related to the administered activity and age of patient. For CT, there are many factors that determine effective dose. Effective dose is dependent on tube current (mA), tube potential (kVp), rotation speed, pitch, slice thickness, patient mass, and the exact volume of the patient that is being imaged. The CT scan may be acquired at exposure parameters similar to those used for diagnostic CT, but more commonly, the tube current is reduced and a localization CT scan of somewhat less than optimal diagnostic quality is obtained. A very low dose CT scan for attenuation correction may also be considered.