Positron emission tomography/computed tomography with 18fluoro-deoxyglucose in the detection of local recurrence and distant metastases of pediatric sarcoma

Rhabdomyosarcoma of the Biliary Tract in Children: Analysis of Single Center Experience

Rhabdomyosarcoma (RMS) of the biliary tract is a rare tumor in children, constituting 0.5-0.8% of all pediatric RMS. Still, it is the most common malignancy in this location in children. Due to its rarity and location, it may cause diagnostic and treatment difficulties. Above all, there are no therapeutic guidelines specific for this tumor location. The aim of the study was to present an analysis of our experience with the treatment of children with biliary tract rhabdomyosarcoma (RMS) and discuss clinical recommendations for this specific location published in the literature. A retrospective analysis of medical records of eight children with biliary tree RMS treated in one center between 1996-2022 was performed. Records of eight children, five boys and three girls aged 2 yrs 6 mo to 16 yrs 9 mo (median-6 yrs) were analyzed. All patients presented with jaundice as the first symptom. In two patients, initial diagnosis of a tumor was established. For the remaining six, the primary diagnoses were as follows: choledochal cyst-one, malformation of the biliary ducts-one, choledocholithiasis-one, cholangitis-three. In four patients, the extrahepatic bile ducts were involved; in four patients, both the intrahepatic and extrahepatic bile ducts were involved. Embryonal RMS was diagnosed in seven patients (three botryoides type). Alveolar RMS was found in one patient. Biopsy (three surgical, four during endoscopic retrograde cholangiopancreatography (ERCP)) was performed in seven patients. One child underwent primary partial tumor resection (R2). Seven patients received neoadjuvant chemotherapy, followed by delayed resection in five, including liver transplantation in one (five were R0). Two patients did not undergo surgery. Radiotherapy was administered in four patients (two in first-line treatment, two at relapse/progression). Six patients (75%) are alive with no evidence of disease, with follow-up ranging from 1.2 yrs to 27 yrs (median 11 yrs. and 4 mo.). Two patients died from disease, 2 y 9 mo and 3 y 7 mo from diagnosis. Children presenting with obstructive jaundice should be evaluated for biliary tract RMS. The treatment strategy should include biopsy and preoperative chemotherapy, followed by tumor resection and radiotherapy for residual disease and in case of relapse.

Positron Emission Tomography/Computed Tomography Transformation of Oncology: Musculoskeletal Cancers

The past 25 years have seen significant growth in the role of positron emission tomography/computed tomography (PET/CT) in musculoskeletal oncology. Substantiative advances in technical capability and image quality have been paralleled by increasingly widespread clinical adoption and implementation. It is now recognized that PET/CT is useful in diagnosis, staging, prognostication, response assessment, and surveillance of bone and soft tissue sarcomas, often providing critical information in addition to conventional imaging assessment. As individualized, precision medicine continues to evolve for patients with sarcoma, PET/CT is uniquely positioned to offer additional insight into the biology and management of these tumors.

The Role of FDG-PET and Whole-Body MRI in High Grade Bone Sarcomas With Particular Focus on Osteosarcoma

Sarcoma represents less than 2% of adult malignancies and about 15% to 20% of malignancies in children and adolescents/young adults. This neoplasm accounts for more than 80 different clinico-pathological entities with different clinical behavior; osteosarcoma and ewing sarcoma are the most frequent primary bone tumors. Because of the general poor prognosis, it is important to find out as many prognostic factors as possible to choose the best therapeutical approach and to correctly schedule the follow-up examinations. Third level imaging such as MRI and PET/CT are of utmost importance in the evaluation of sarcoma patients. The spine and bones in general are optimal sites to be evaluated with FDG PET/CT since the physiological background is low. The standardized uptake value (SUV max, a semiquantitave parameter) is used as a surrogate for proliferative cell rate, and the spatial heterogeneity of FDG distribution within the primary mass as a surrogate for malignancy. In several studies SUVmax was a predictive value for overall survival and progression-free survival. Whole-body MRI is a well-established technique for systemic, radiation-free evaluation, which is mostly applied in the oncological field. WB-MRI provides a combination of anatomical and functional sequences and is useful specifically in the evaluation of disease in organs with relatively high background activity such as the brain, liver, kidney, and spinal canal. These technologies provide accurate staging (also useful to drive the biopsy towards the most active foci in large heterogeneous masses), therapy assessment, relapse detection of local recurrence and distance metastasis but also prognostic indexes, in the context of whole body diagnostic procedures. This paper will provide an overview of the role and added value of PET/CT and WB-MRI in bone sarcomas particular focus on osteosarcoma. We also analyzed the role of the PET/CT and MRI for target delineation of radiation therapy and we and we will do an analysis of future prospects as new tracer non FDG.

Fluorine-18-fluorodeoxyglucose (FDG) positron emission tomography (PET) computed tomography (CT) for the detection of bone, lung, and lymph node metastases in rhabdomyosarcoma

BACKGROUND

Rhabdomyosarcoma (RMS) is the most common paediatric soft-tissue sarcoma and can emerge throughout the whole body. For patients with newly diagnosed RMS, prognosis for survival depends on multiple factors such as histology, tumour site, and extent of the disease. Patients with metastatic disease at diagnosis have impaired prognosis compared to those with localised disease. Appropriate staging at diagnosis therefore plays an important role in choosing the right treatment regimen for an individual patient. Fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) is a functional molecular imaging technique that uses the increased glycolysis of cancer cells to visualise both structural information and metabolic activity. 18F-FDG-PET combined with computed tomography (CT) could help to accurately stage the extent of disease in patients with newly diagnosed RMS. In this review we aimed to evaluate whether 18F-FDG-PET could replace other imaging modalities for the staging of distant metastases in RMS.

OBJECTIVES

To determine the diagnostic accuracy of 18F-FDG-PET/CT imaging for the detection of bone, lung, and lymph node metastases in RMS patients at first diagnosis.

SEARCH METHODS

We searched MEDLINE in PubMed (from 1966 to 23 December 2020) and Embase in Ovid (from 1980 to 23 December 2020) for potentially relevant studies. We also checked the reference lists of relevant studies and review articles; scanned conference proceedings; and contacted the authors of included studies and other experts in the field of RMS for information about any ongoing or unpublished studies. We did not impose any language restrictions.

SELECTION CRITERIA

We included cross-sectional studies involving patients with newly diagnosed proven RMS, either prospective or retrospective, if they reported the diagnostic accuracy of 18F-FDG-PET/CT in diagnosing lymph node involvement or bone metastases or lung metastases or a combination of these metastases. We included studies that compared the results of the 18F-FDG-PET/CT imaging with those of histology or with evaluation by a multidisciplinary tumour board as reference standard.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, data extraction, and methodological quality assessement according to Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2). We analysed data for the three outcomes (nodal involvement and lung and bone metastases) separately. We used data from the 2 × 2 tables (consisting of true positives, false positives, true negatives, and false negatives) to calculate sensitivity and specificity in each study and corresponding 95% confidence intervals. We did not consider a formal meta-analysis to be relevant because of the small number of studies and substantial heterogeneity between studies.

MAIN RESULTS

Two studies met our inclusion criteria. The diagnostic accuracy of 18F-FDG-PET/CT was reported in both studies, which included a total of 36 participants. We considered both studies to be at high risk of bias for the domain reference standard. We considered one study to be at high risk of bias for the domain index test and flow and timing. Sensitivity and specificity of 18F-FDG-PET/CT for the detection of bone metastases was 100% in both studies (95% confidence interval (CI) for sensitivity was 29% to 100% in study one and 40% to 100% in study two; 95% CI for specificity was 83% to 100% in study one and 66% to 100% in study two). The reported sensitivity of 18F-FDG-PET/CT for the detection of lung metastases was not calculated since only two participants in study two showed lung metastases, of which one was detected by 18F-FDG-PET/CT. Reported specificity was 96% in study one (95% CI 78% to 100%) and 100% (95% CI 72% to 100%) in study two. The reported sensitivity for the detection of nodal involvement was 100% (95% CI 63% to 100% in study one and 40% to 100% in study two); the reported specificity was 100% (95% CI 78% to 100%) in study one and 89% (95% CI 52% to 100%) in study two.

AUTHORS' CONCLUSIONS

The diagnostic accuracy of 18F-FDG-PET/CT for the detection of bone, lung, and lymph node metastases was reported in only two studies including a total of only 36 participants with newly diagnosed RMS. Because of the small number of studies (and participants), there is currently insufficient evidence to reliably determine the diagnostic accuracy of 18F-FDG-PET/CT in the detection of distant metastases. Larger series evaluating the diagnostic accuracy of 18F-FDG-PET/CT for the detection of metastases in patients with RMS are necessary.

Post-treatment FDG PET/CT predicts progression-free survival in young patients with small round blue cell tumors: Ewing sarcoma and PNET

PURPOSE

To determine if post-treatment F-18 FDG PET/CT results (overall positive findings, specific localizations) are independent predictors of disease progression in young patients with Ewing sarcoma and Primitive neuroectodermal tumor.

METHOD

A consecutive sample of 48 patients (age 14 ± 5 years, 32 male) was referred to F-18 FDG PET/CT for the suspected progression of Ewing sarcoma (39 patients) and Primitive neuroectodermal tumor (PNET) (9 patients) and followed-up clinically for 4.3 ± 2.3 years after F-18 FDG PET/CT (range 1-8 years). The diagnostic value of F-18 FDG PET/CT was determined in comparison to the biopsy. Kaplan-Meier analysis was used to compare progression-free survival between the groups with positive and negative F-18 FDG PET/CT findings. Variables included in the Cox regression for predicting the progression-free survival were sex, age, F-18 FDG PET/CT findings, MDCT findings, and MR ratio.

RESULTS

F-18 FDG PET/CT findings were positive in 32 (67 %) patients (sensitivity 93.7 %, specificity 87.5 %, accuracy 91.7 %) with an average SUVmax of 5.8 ± 3.2 (95 % CI 4.8-7.1). The progression-free survival was significantly lower (p = 0.001) in patients with positive F-18 FDG PET/CT findings (median 28 months) and when recurrence was located in bones, soft tissues, and muscles (p = 0.02, median 21 months). The significant predictors of the disease progression were the overall positive F-18 FDG PET/CT findings (HR 8.36, p = 0.004) and, specifically, the local recurrence in the bone with infiltration of soft tissue/muscles (HR 4.08, p = 0.003).

CONCLUSION

Post-treatment F-18 FDG PET/CT findings are useful for predicting the progression of Ewing sarcoma and PNET and should be included in the clinical monitoring of these patients.

Clinical and Prognostic Role of 18F-FDG PET/CT in Pediatric Ewing Sarcoma

Ewing sarcoma (ES) is one of the most common pediatric solid tumors with aggressive behavior and unfavorable survival. In this study, we evaluated the diagnostic accuracy of baseline and restaging fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) scans and their possible prognostic role in pediatric ES. We evaluated 17 patients who underwent a total of 27 18F-FDG-PET/CT scans (10 for staging and 17 for restaging). The PET images were analyzed visually and semiquantitatively by measuring SUVmean, SUVmax, SUVlbm, SUVbsa, MTV, and TLG. Moreover, PET/CT results were compared with other conventional imaging (CI) results. Among 10 baseline PET/CT scan results, 9 were positive and 1 not valuable by interference; baseline PET/CT and CI were concordant in 7 cases and discordant in 2, with pulmonary micrometastases not detected by PET/CT. Among 17 restaging PET/CT scan results, 9 were positive and 8 negative; CI and restaging PET/CT were concordant in 9 cases and discordant in 8. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of restaging 18F-FDG-PET/CT were 73%, 83%, 89%, 62.5%, and 76%, respectively. After a median follow-up of 20 months, relapse/progression occurred in 8 patients and death in 5. A positive 18F-FDG-PET/CT at restaging was significantly associated with shorter overall survival compared with unremarkable PET/CT at the same timepoint, but not with progression-free survival. Instead, metabolic PET/CT features were not correlated with outcome. 18F-FDG-PET/CT showed a good diagnostic performance in pediatric ES; except for pulmonary micrometastases, PET/CT was better than CI at restaging. Only restaging PET/CT result was significantly correlated with overall survival.

Applications of PET-MRI in musculoskeletal disease

New integrated PET-MRI systems potentially provide a complete imaging modality for diagnosis and evaluation of musculoskeletal disease. MRI is able to provide excellent high-resolution morphologic information with multiple contrast mechanisms that has made it the imaging modality of choice in evaluation of many musculoskeletal disorders. PET offers incomparable abilities to provide quantitative information about molecular and physiologic changes that often precede structural and biochemical changes. In combination, hybrid PET-MRI can enhance imaging of musculoskeletal disorders through early detection of disease as well as improved diagnostic sensitivity and specificity. The purpose of this article is to review emerging applications of PET-MRI in musculoskeletal disease. Both clinical applications of malignant musculoskeletal disease as well as new opportunities to incorporate the molecular capabilities of nuclear imaging into studies of nononcologic musculoskeletal disease are discussed. Lastly, we discuss some of the technical considerations and challenges of PET-MRI as they specifically relate to musculoskeletal disease.

LEVEL OF EVIDENCE

5 TECHNICAL EFFICACY: Stage 3 J. Magn. Reson. Imaging 2018;48:27-47.

Primary Intra-abdominal Ewing's Sarcoma in Adults: A Multimodality Imaging Spectrum

Ewing sarcoma (ES) and peripheral primitive neuroectodermal tumor are part of a spectrum of neoplastic diseases known as the ES family of tumors, which also includes extraosseous ES, peripheral primitive neuroectodermal tumor, malignant small-cell tumor of the thoracopulmonary region (Askin's tumor), and atypical ES. Although imaging features of these tumors have been previously described, extensive discussion about intra-abdominal manifestations is scarce in the literature. We present an imaging spectrum of these tumors in the abdomen and pelvis with particular attention to multimodality approach for staging and restaging.

Future Perspective of the Application of Positron Emission Tomography-Computed Tomography-MR Imaging in Musculoskeletal Disorders

Fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) is the imaging method of choice in sarcoma patients. PET may help in diagnosis, grading, staging, biopsy guidance, monitoring response to therapy, restaging for recurrence, and prognosis. 18F-FDG-PET/MRI combines the higher tissue contrast of MRI in the study of soft-tissue lesions and the peculiarities of PET imaging that allow the characterization of tissues. The use of 18F-FDG-PET/MRI in these patients has reduces the radiation dose, which is of great importance, particularly in children. Data support the routine use of 18F-FDG-PET either using CT or MRI in patients with sarcoma.

Effectiveness of 18F-FDG PET/CT in the diagnosis, staging and recurrence monitoring of Ewing sarcoma family of tumors: A meta-analysis of 23 studies

BACKGROUND

To investigate the value of positron emission tomography (PET) and PET/computed tomography (CT) using fluorine-18-fluorodeoxyglucose (F-FDG) in the diagnosis, staging, restaging and recurrence monitoring of Ewing sarcoma family of tumors (ESFTs), a meta-analysis was performed through systematically searching PubMed, Embase, and Cochrane Central library to retrieve articles.

METHODS

After screening and diluting out the articles that met inclusion criteria to be used for statistical analysis the pooled evaluation indexes including sensitivity, specificity, and diagnostic odd ratio (DOR) as well as the summary receiver operating characteristic curve (SROC) were calculated involving diagnostic data (true positive, false positive, false negative, and true negative) extracted from original studies.

RESULTS

Screening determined that out of 2007, 23 studies involving a total of 524 patients were deemed viable for inclusion in the meta-analysis. The results of the analysis showed that the sensitivity and specificity were at 86% and 80%, respectively. Additionally, a satisfactory accuracy of F-FDG PET and PET/CT was observed in detecting ESFT recurrence, lung metastasis, and osseous metastasis.

CONCLUSION

This meta-analysis suggests that F-FDG PET and PET/CT with an extremely high accuracy could be considered a valuable method for detecting distant metastasis and post-operational recurrence of ESFT, which might have a profound impact on the development of treatment protocols for ESFT.

Pediatric Musculoskeletal Imaging: The Indications for and Applications of PET/Computed Tomography

The use of PET/computed tomography (CT) for the evaluation and management of children, adolescents, and young adults continues to expand. The principal tracer used is 18F-fluorodeoxyglucose and the principal indication is oncology, particularly musculoskeletal neoplasms. The purpose of this article is to review the common applications of PET/CT for imaging of musculoskeletal issues in pediatrics and to introduce the use of PET/CT for nononcologic issues, such as infectious/inflammatory disorders, and review the use of 18F-sodium fluoride in trauma and sports-related injuries.

Applications of PET/CT and PET/MR Imaging in Primary Bone Malignancies

Primary bone malignancies are characterized with anatomic imaging. However, in recent years, there has been an increased interest in PET/computed tomography scanning and PET/MRI with fludeoxyglucose F 18 for evaluating and staging musculoskeletal neoplasms. These hybrid imaging modalities have shown promise largely owing to their high sensitivity, ability to perform more thorough staging, and ability to monitor treatment response. This article reviews the current role of PET/computed tomography scanning and PET/MRI in primary malignancies of bone, with an emphasis on imaging characteristics, clinical usefulness, and current limitations.

Recurrence of Ewing sarcoma: Is detection by imaging follow-up protocol associated with survival advantage?

BACKGROUND

The Cooperative Ewing Sarcoma Study and the Late Effects Surveillance System of the Society for Paediatric Oncology and Haematology recommend a structured follow-up imaging protocol (FUIP) for patients with Ewing sarcoma (EwS) with decreasing frequency of imaging over the first 5 years. The present study aims to assess the effectiveness of the FUIP for EwS patients regarding survival after relapse.

PATIENTS AND METHODS

A retrospective multicenter analysis on 160 eligible patients with EwS recurrence was performed. Potential survival differences following recurrence diagnosis between patients with protocol-detected and symptomatic relapse were investigated using the Kaplan-Meier method. Additional subgroup analyses were performed on the relapse type. Overall survival (OS) was calculated from diagnosis of relapse to last follow-up or death.

RESULTS

In the multicenter analysis, recurrence was detected by FUIP in 77 of 160 patients (48%) and due to symptoms in 83 patients (52%). Regarding the entire study population, OS was significantly superior in patients with protocol-detected relapse compared to patients with symptomatic relapse (median, 2.4 vs. 1.2 years; P < 0.001). In the subgroup analyses, patients whose lung recurrences were detected by the FUIP experienced longer survival after recurrence than those whose recurrences were detected symptomatically (P = 0.023). In the 83 symptomatic patients, pain was the most prevalent symptom of relapse (72%).

CONCLUSION

FUIP may benefit survival in EwS relapse, especially in lung recurrence. Pain was the leading symptom of relapse.

Ewing sarcoma during follow-up

AIM

To evaluate the performance of a prospectively defined follow-up imaging protocol that includes FDG-PET(/CT) to detect tumour recurrence in Ewing sarcoma (EwS) before becoming symptomatic.

METHODS

Imaging results and clinical data during follow-up were retrospectively analysed from all patients treated successfully within the EURO E.W.I.N.G. 99 trial at the University Hospital Münster, Germany. All patients received follow-up imaging according to a comprehensive protocol that included regular X-ray, CT, MRI, bone scan and PET(/CT), albeit not all on the same day and with varying intervals for the different modalities.

RESULTS

80 of 105 patients underwent follow-up at our institution after complete remission. 30 patients had recurrent tumour during the follow-up period of 3.6 years on average. 19 recurrences (63%) were detected by scheduled imaging before the advent of clinical symptoms. The majority of these recurrences (8 out of 19; 42%) was detected first by PET/ CT (and confirmed with additional imaging thereafter), even though the total number of PET/CTs was comparatively low (138) and PET/CT was not systematically scheduled before other imaging techniques. Recurrences detected by bone scan were also detectable by PET.

CONCLUSIONS

The implemented follow-up protocol was effective in the detection of EwS recurrence before the advent of symptoms. Most cases of those detected before onset of symptoms were detected by PET/CT first. This hybrid imaging modality should therefore be considered in the routine follow-up of EwS patients, as is standard in our hospital. In combination with PET, low-dose chest CT seems to be sufficient in the detection of small pulmonary nodules.

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.

Paediatric nuclear medicine imaging

BACKGROUND

Nuclear medicine imaging explores tissue viability and function by using radiotracers that are taken up at cellular level with different mechanism. This imaging technique can also be used to assess blood flow and transit through tubular organs. Nuclear medicine imaging has been used in paediatrics for decades and this field is continuously evolving.

SOURCES OF DATA

The data presented comes from clinical experience and some milestone papers on the subject.

AREAS OF AGREEMENT

Nuclear medicine imaging is well-established in paediatric nephro-urology in the context of urinary tract infection, ante-natally diagnosed hydronephrosis and other congenital renal anomalies. Also, in paediatric oncology, I-123-meta-iodobenzyl-guanidine has a key role in the management of children with neuroblastic tumours. Bone scintigraphy is still highly valuable to localize the source of symptoms in children and adolescents with bone pain when other imaging techniques have failed. Thyroid scintigraphy in neonates with congenital hypothyroidism is the most accurate imaging technique to confirm the presence of ectopic functioning thyroid tissue.

AREAS OF CONTROVERSY

Radionuclide transit studies of the gastro-intestinal tract are potentially useful in suspected gastroparesis or small bowel or colonic dysmotility. However, until now a standardized protocol and a validated normal range have not been agreed, and more work is necessary. Research is ongoing on whether magnetic resonance imaging (MRI), with its great advantage of great anatomical detail and no ionizing radiations, can replace nuclear medicine imaging in some clinical context. On the other hand, access to MRI is often difficult in many district general hospitals and general anaesthesia is frequently required, thus adding to the complexity of the examination.

GROWING POINTS

Patients with bone pain and no cause for it demonstrated on MRI can benefit from bone scintigraphy with single photon emission tomography and low-dose computed tomography. This technique can identify areas of mechanical stress at cortical bone level, difficult to demonstrate on MRI, which can act as pain generators. Positron emission tomography (PET) is being tested in the staging, response assessment and at the end of treatment of several paediatric malignancies. PET is becoming more widely utilized in neurology in the pre-surgical assessment of some children with drug resistant epilepsy.

AREAS TIMELY FOR DEVELOPING RESEARCH

The use of PET/MRI scanners is very attractive as it combines benefits of MR imaging with the assessment of cellular viability and metabolism with PET in one examination. This imaging technique will allow important research on tumour in-vivo metabolism (possible applications include lymphomas, neuroblastomas, malignant germ cell tumours andbrain tumours), with the aim of offering a personalized biological profile of the tumour in a particular patient. Ground-breaking research is also envisaged in neurosciences, especially in epilepsy, using PET tracers that would enable a better identification of the epileptogenic focus, and in psychiatry, with the use of radiolabeled neurotransmitters. In paediatric nephro-urology, the identification of the asymptomatic child with ante-natally diagnosed hydronephrosis at risk of losing renal parenchymal function if left untreated is another area of active research involving radionuclide renography.

FDG-PET/CT in the Postoperative Period: Utility, Expected Findings, Complications, and Pitfalls

FDG-PET/CT as a modality is increasingly used for detection of recurrence and for restaging in patients with clinical suspicion of malignancy, as well as in patients with elevated tumor markers. However, there are many pitfalls in the interpretation of these scans when the studies are performed after some treatment. Some of these are attributed to normal physiological distribution and are compounded when there are inflammatory changes occurring after surgery. The body's inherent response to the surgical insult results in this inflammation. In addition, there are also complications that can happen following surgery, causing increased FDG uptake. Despite various fallacies, FDG-PET/CT provides valuable information in evaluation of residual and recurrent malignant disease. In this article, we aim to describe some of these postsurgical changes secondary to inflammation, common surgical complications, and finally, the utility of FDG-PET/CT in these patients to detect recurrent disease, even in the background of postsurgical changes.

Imaging of Complications After Limb Prostheses Implantation in Children with Bone Tumors

BACKGROUND

Tumors of the developmental age are an important problem in clinical practice. Primary bone tumors constitute 1-1.5% of all tumors, and 7% of all tumors diagnosed in the developmental age. The aim of the study was to assess the capabilities of imaging methods in diagnosing complications of limb endoprostheses in children with osteoarticular tumors.

MATERIAL/METHODS

We included 155 patients with limb endoprostheses, aged 7-26 years. There were 113 patients with knee prostheses, 1 patient with bilateral knee prostheses, 16 patients with shoulder prostheses, 14 patients with hip prostheses, 11 patients with hip and knee prostheses, and 1 patient with a femoral prosthesis. All patients underwent plain radiography and an ultrasound study.

RESULTS

Complications were found in 50 patients (32% of all patients). The following complications were seen - inflammatory changes in soft tissues and bones (12 patients, 7.7%), stump fractures (11 patients, 7%), lack of elongation effect or shortening of the prosthesis (7 patients, 4.5%), prosthesis fractures (4 patients, 2.5%), crural fractures (4 patients, 2.5%), loosening of the prosthesis (3 patients, 1.9%), joint dislocation (2 patients, 1.3%), stump and prosthesis fracture (1 patient, 0.6%) and local recurrence (6 patients, 3.9%). Prostheses were exchanged for the following reasons - fractures (5 patients, 3.2%), inflammation (2 patients with 3 exchanges, 1.9%). Local recurrence and inflammation were confirmed by a biopsy.

CONCLUSIONS

Radiography and ultrasonography are of crucial importance in monitoring patients after implantation of limb endoprostheses. The findings did not require confirmation in additional studies: CT and MRI. Suspicion of local recurrence and inflammation required a biopsy confirmation.

Comparison of (18) F-FDG-PET-CT and Bone Scintigraphy for Evaluation of Osseous Metastases in Newly Diagnosed and Recurrent Osteosarcoma

BACKGROUND

Bone scintigraphy (BS) is used to detect osseous metastases in osteosarcoma. (18) F-fluorodeoxyglucose-positron emission tomography-computed tomography ((18) F-FDG-PET-CT) is being increasingly used for staging. We compared the sensitivity, specificity, and diagnostic accuracy of (18) F-FDG-PET-CT and BS for detecting osseous metastases in osteosarcoma.

METHODS

We retrospectively reviewed 39 patients with osteosarcoma who had paired PET-CT and BS at diagnosis and/or first recurrence from 2003 to 2012. Imaging studies were reviewed by two pediatric imaging specialists who were blinded to results of the opposing modality and reference standard. Reviewers categorized lesions as benign, malignant, or indeterminate. Reference standard for lesion histology was biopsy or clinical follow-up. Diagnostic performance of PET-CT, BS, and combined modalities were determined.

RESULTS

There were 40 examinations from 39 patients and 65 distant lesions were evaluated. Median age was 12 years (range 5-19 years). Four patients had 15 osseous metastases at diagnosis (two biopsied and 13 clinically), and two had five osseous metastases at recurrence (one biopsied and five clinically). For distant sites, sensitivity, specificity, and diagnostic accuracy were 79%, 89% and 86% for PET-CT, 32%, 96%, and 77% for BS, and 95%, 85%, and 88% for PET-CT/BS combined. Sensitivity of PET-CT was superior to BS (P = 0.035); combined imaging modalities were superior to BS (P < 0.001) but not better than PET-CT alone (P = 0.25). Specificity for BS approached significance compared to combined imaging (P = 0.063). Examination-based analysis yielded similar results between individual and combined imaging modalities.

CONCLUSIONS

(18) F-FDG-PET-CT demonstrated superior sensitivity over BS for detecting osseous metastases, supporting the use of (18) F-FDG-PET-CT for staging of osteosarcoma.

The Possible Role of PET Imaging Toward Individualized Management of Bone and Soft Tissue Malignancies

This article presents fluorodeoxyglucose PET/computed tomography for the evaluation of soft tissue sarcomas. Its clinical impact is discussed analyzing all the clinical information provided when applied in different phases of the disease. A special paragraph is dedicated to the use of functional imaging for driving the biopsy.

Qualitative FDG PET Image Assessment Using Automated Three-Segment MR Attenuation Correction Versus CT Attenuation Correction in a Tertiary Pediatric Hospital: A Prospective Study

OBJECTIVE

The purpose of this study was to systematically evaluate the diagnostic quality of (18)F-FDG PET images generated using MR attenuation correction (MRAC) compared with those images generated using CT attenuation correction (CTAC) in a pediatric population.

SUBJECTS AND METHODS

Forty-two patients (mean age, 12.8 years; percentage who were male, 57%) who were referred for 62 indicated whole-body PET/CT studies were prospectively recruited to undergo PET/MRI examinations during the same clinic visit in which PET/CT was performed. MRAC was performed using an automatic three-segment model. Three nuclear radiologists scored the diagnostic quality of the PET images generated by MRAC and CTAC using a Likert scale (range of scores, 1-5). Images graded with a score of 1-3 were considered clinically unacceptable, whereas images with a score of 4-5 were considered clinically acceptable. A Wilcoxon signed-rank test was used to compare differences in the grading of PET/MRI and PET/CT images. The Fisher exact test was used to evaluate potential differences in clinically acceptable image quality and the presence of artifact. Fleiss kappa statistics were used to examine interobserver agreement.

RESULTS

There was no statistically significant difference in the proportion of PET images generated with MRAC and CTAC for which image quality was considered clinically acceptable. A total of 3.9% of PET assessments generated with MRAC were of unacceptable image quality, compared with 2.2% of PET images generated with CTAC. Two of the three radiologists who reviewed the PET images reported the presence of artifacts more often on MRAC-derived images, and they graded the mean quality of these images 0.48 and 0.29 points lower on the 5-point Likert scale than they graded the mean quality of CTAC-derived images (p < 0.0001). Interobserver agreement was fair (κ = 0.39).

CONCLUSION

The diagnostic quality of PET images obtained from a pediatric population with the use of an automatic three-segmentation MRAC method was comparable to that of PET images obtained with the use of CTAC.

Performance of Positron Emission Tomography and Positron Emission Tomography/Computed Tomography Using Fluorine-18-Fluorodeoxyglucose for the Diagnosis, Staging, and Recurrence Assessment of Bone Sarcoma: A Systematic Review and Meta-Analysis

To investigate the performance of fluorine-18-fluorodeoxyglucose (F-FDG) positron emission tomography (PET) and PET/computed tomography (CT) in the diagnosis, staging, restaging, and recurrence surveillance of bone sarcoma by systematically reviewing and meta-analyzing the published literature.To retrieve eligible studies, we searched the MEDLINE, Embase, and the Cochrane Central library databases using combinations of following Keywords: "positron emission tomography" or "PET," and "bone tumor" or "bone sarcoma" or "sarcoma." Bibliographies from relevant articles were also screened manually. Data were extracted and the pooled sensitivity, specificity, and diagnostic odds ratio (DOR), on an examination-based or lesion-based level, were calculated to appraise the diagnostic accuracy of F-FDG PET and PET/CT. All statistical analyses were performed using Meta-Disc 1.4.Forty-two trials were eligible. The pooled sensitivity and specificity of PET/CT to differentiate primary bone sarcomas from benign lesions were 96% (95% confidence interval [CI], 93-98) and 79% (95% CI, 63-90), respectively. For detecting recurrence, the pooled results on an examination-based level were sensitivity 92% (95% CI, 85-97), specificity 93% (95% CI, 88-96), positive likelihood ratio (PLR) 10.26 (95% CI, 5.99-17.60), and negative likelihood ratio (NLR) 0.11 (95% CI, 0.05-0.22). For detecting distant metastasis, the pooled results on a lesion-based level were sensitivity 90% (95% CI, 86-93), specificity 85% (95% CI, 81-87), PLR 5.16 (95% CI, 2.37-11.25), and NLR 0.15 (95% CI, 0.11-0.20). The accuracies of PET/CT for detecting local recurrence, lung metastasis, and bone metastasis were satisfactory. Pooled outcome estimates of F-FDG PET were less complete compared with those of PET/CT.F-FDG PET and PET/CT showed a high sensitivity for diagnosing primary bone sarcoma. Moreover, PET/CT demonstrated excellent accuracy for the staging, restaging, and recurrence surveillance of bone sarcoma. However, to avoid misdiagnosis, pathological examination or long-term follow-up should be carried out for F-FDG-avid lesions in patients with suspected bone sarcoma.

Value of FDG PET/CT in Patient Management and Outcome of Skeletal and Soft Tissue Sarcomas

Fluorodeoxyglucose (FDG)-PET/computed tomography (CT) has been increasingly used in bone and soft tissue sarcomas and provides advantages in the initial tumor staging, tumor grading, therapy assessment, and recurrence detection. FDG-PET/CT metabolic parameters are reliable predictors of survival in sarcomas and could be implemented in risk stratification models along with other prognostic factors in these patients.

Use of PET/CT instead of CT-only when planning for radiation therapy does not notably increase life years lost in children being treated for cancer

BACKGROUND

PET/CT may be more helpful than CT alone for radiation therapy planning, but the added risk due to higher doses of ionizing radiation is unknown.

OBJECTIVE

To estimate the risk of cancer induction and mortality attributable to the [F-18]2-fluoro-2-deoxyglucose (FDG) PET and CT scans used for radiation therapy planning in children with cancer, and compare to the risks attributable to the cancer treatment.

MATERIALS AND METHODS

Organ doses and effective doses were estimated for 40 children (2-18 years old) who had been scanned using PET/CT as part of radiation therapy planning. The risk of inducing secondary cancer was estimated using the models in BEIR VII. The prognosis of an induced cancer was taken into account and the reduction in life expectancy, in terms of life years lost, was estimated for the diagnostics and compared to the life years lost attributable to the therapy. Multivariate linear regression was performed to find predictors for a high contribution to life years lost from the radiation therapy planning diagnostics.

RESULTS

The mean contribution from PET to the effective dose from one PET/CT scan was 24% (range: 7-64%). The average proportion of life years lost attributable to the nuclear medicine dose component from one PET/CT scan was 15% (range: 3-41%). The ratio of life years lost from the radiation therapy planning PET/CT scans and that of the cancer treatment was on average 0.02 (range: 0.01-0.09). Female gender was associated with increased life years lost from the scans (P < 0.001).

CONCLUSION

Using FDG-PET/CT instead of CT only when defining the target volumes for radiation therapy of children with cancer does not notably increase the number of life years lost attributable to diagnostic examinations.

Posttreatment imaging of pediatric musculoskeletal tumors

Pediatric patients who are diagnosed with musculoskeletal tumors often require serial imaging both during and after treatment. Although many of the treatments used in adults overlap with those used in children and adolescents, the growing skeleton presents specific challenges that require a unique approach. Surgical treatment of benign osseous lesions typically requires only curettage and bone grafting, whereas that of osseous malignancies generally consists of wide excision and limb salvage, with either endoprosthetic or biologic reconstruction. Current conventional endoprostheses consist of modular components that allow intraoperative customization; however, if there is great potential for future growth, an expandable endoprosthesis may be required. Biologic reconstruction may consist of an allograft and/or autograft and, in some circumstances, can spare the growth plates in a child, thereby allowing normal growth. Expected posttreatment imaging findings in soft-tissue tumors may include muscle flaps and postoperative fluid collections. Medical treatment, including radiation therapy and chemotherapy, can have predictable imaging manifestations, including signal alterations in bone marrow, muscle, and subcutaneous fat. Finally, treatment complications may manifest with clinical symptoms and include infection or mechanical failure, although other complications such as local tumor recurrence may go clinically undetected until surveillance imaging. Familiarity with the expected posttreatment imaging findings in pediatric patients with musculoskeletal tumors can aid in the detection of complications.

Value of 18F-FDG PET and PET/CT for evaluation of pediatric malignancies

Successful management of solid tumors in children requires imaging tests for accurate disease detection, characterization, and treatment monitoring. Technologic developments aim toward the creation of integrated imaging approaches that provide a comprehensive diagnosis with a single visit. These integrated diagnostic tests not only are convenient for young patients but also save direct and indirect health-care costs by streamlining procedures, minimizing hospitalizations, and minimizing lost school or work time for children and their parents. (18)F-FDG PET/CT is a highly sensitive and specific imaging modality for whole-body evaluation of pediatric malignancies. However, recent concerns about ionizing radiation exposure have led to a search for alternative imaging methods, such as whole-body MR imaging and PET/MR. As we develop new approaches for tumor staging, it is important to understand current benchmarks. This review article will synthesize the current literature on (18)F-FDG PET/CT for tumor staging in children, summarizing questions that have been solved and providing an outlook on unsolved avenues.

Pediatric bone sarcoma: diagnostic performance of ¹⁸F-FDG PET/CT versus conventional imaging for initial staging and follow-up

OBJECTIVE

The purpose of this study was to compare the diagnostic performance of (18)F-FDG PET/CT and conventional imaging for staging and follow-up of pediatric osteosarcoma and skeletal Ewing sarcoma.

MATERIALS AND METHODS

We calculated sensitivity, specificity, and accuracy of PET/CT and conventional imaging (CT, MRI, bone scanning) for sites of disease and number of lesions. Diagnostic benefit, defined as better characterization of lesions, was evaluated on a per-scan basis, comparing PET/CT and conventional imaging.

RESULTS

A total of 412 lesions were characterized by imaging in 64 patients (20, osteosarcoma; 44, Ewing sarcoma). For osteosarcoma patients PET/CT was available only at follow-up, where it proved more accurate than conventional imaging for the detection of bone lesions (accuracy, 95% vs 67% for CT and 86% for MRI) and complementary to CT in evaluating lung nodules (sensitivity, 84% vs 94%; specificity, 79% vs 71%) with diagnostic benefit in 18% of examinations. In patients with Ewing sarcoma, PET/CT tended to perform better during follow-up than at initial staging (accuracy, 85% vs 69%). For lung findings, PET/CT was more specific than CT but was less sensitive. The diagnostic benefit of PET/CT was greater at staging (28%) than during followup (9%). On a per-patient basis, PET/CT provided diagnostic benefit in 21 of 44 patients with Ewing sarcoma and nine of 20 patients with osteosarcoma at least once during clinical management.

CONCLUSION

FDG PET/CT provides diagnostic benefit in Ewing sarcoma and osteosarcoma, with the exception of small lung nodules. Prospective studies are needed to define the best imaging algorithm and combination of tests in the staging and follow-up of patients with pediatric bone sarcoma.

PET/CT-guided treatment planning for paediatric cancer patients: a simulation study of proton and conventional photon therapy

OBJECTIVE

To investigate the impact of including fluorine-18 fludeoxyglucose ((18)F-FDG) positron emission tomography (PET) scanning in the planning of paediatric radiotherapy (RT).

METHODS

Target volumes were first delineated without and subsequently re-delineated with access to (18)F-FDG PET scan information, on duplicate CT sets. RT plans were generated for three-dimensional conformal photon RT (3DCRT) and intensity-modulated proton therapy (IMPT). The results were evaluated by comparison of target volumes, target dose coverage parameters, normal tissue complication probability (NTCP) and estimated risk of secondary cancer (SC).

RESULTS

Considerable deviations between CT- and PET/CT-guided target volumes were seen in 3 out of the 11 patients studied. However, averaging over the whole cohort, CT or PET/CT guidance introduced no significant difference in the shape or size of the target volumes, target dose coverage, irradiated volumes, estimated NTCP or SC risk, neither for IMPT nor 3DCRT.

CONCLUSION

Our results imply that the inclusion of PET/CT scans in the RT planning process could have considerable impact for individual patients. There were no general trends of increasing or decreasing irradiated volumes, suggesting that the long-term morbidity of RT in childhood would on average remain largely unaffected.

ADVANCES IN KNOWLEDGE

(18)F-FDG PET-based RT planning does not systematically change NTCP or SC risk for paediatric cancer patients compared with CT only. 3 out of 11 patients had a distinct change of target volumes when PET-guided planning was introduced. Dice and mismatch metrics are not sufficient to assess the consequences of target volume differences in the context of RT.

A child with unresectable biliary rhabdomyosarcoma: 48-month disease-free survival after liver transplantation

We describe here a two-yr-old boy with biliary RMS successfully treated by chemotherapy and LT. The child presented with obstructive jaundice at 20 months of age. A mildly vascularized, non-calcified, partially cystic lesion was visualized in the left hepatic lobe. Solid infiltration of the common bile duct and of both left and right hepatic ducts was suspected. Liver biopsy suggested a botryoid-type embryonal RMS originating from the biliary tract. After extrahepatic spread of the tumor was excluded, a biliary drain was applied and neoadjuvant chemotherapy was started. After the treatment, although reduced in volume, the mass was still unresectable without aggressive surgery and gross residual disease. LT with a reduced segment II/III graft was performed four months after diagnosis. The patient received six cycles of adjuvant chemotherapy, and he is alive and recurrence-free 48 months post-transplantation. A posteriori, the transplant might have possibly been avoided with an aggressive resection with biliary reconstruction. Nevertheless, although the risk of the transplant has to be balanced against the chemoresponsiveness of the tumor, the four-yr disease-free survival of this patient suggests that, when coupled with effective chemotherapy, transplantation might be considered a potential treatment for unresectable biliary RMS.

Role of FDG-PET/CT for monitoring soft tissue tumors

The aim of the current study was to evaluate the limitations of 2-deoxy-2-F¹⁸-fluoro-D-glucose positron emission tomography combined with computed tomography (FDG-PET/CT) when monitoring soft tissue tumors. The diagnostic criteria of malignancy was defined as the tumor having a maximum standardized uptake value (SUVmax) ≥2.0 and a maximum diameter ≥5 cm as measured using FDG-PET/CT. One-hundred-and-thirteen patients, that were either included in the criteria or not, were compared. In addition, the values of SUVmax of the primary tumor and relapse in 12 patients were evaluated. The Kaplan-Meier analysis demonstrated that patients with tumors measuring ≥5 cm size and ≥2.0 SUVmax were associated with a worse survival rate. Among the 12 patients with relapse, statistical significances were detected in the tumor diameters, however, not in the SUVmax values. Thus, the criteria identified patients that were associated with a poor prognosis, and the SUVmax of distant metastases and local recurrences were identified to be significantly affected by tumor size.

PET/MRI Imaging in High-Risk Sarcoma: First Findings and Solving Clinical Problems

Simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI) is a new whole-body hybrid PET/MR imaging technique that combines metabolic and cross-sectional diagnostic imaging. Since the use of MRI in imaging of soft-tissue sarcoma is extremely beneficial, investigation of the combined PET/MRI is of great interest. In this paper, we present three cases and first data. Combined PET/MRI technique can support the process of clinical decision-making and give answers to some meaningful questions when treating patients with STS. Therefore, the combined modality of simultaneous PET/MRI offers new pieces to the puzzle of sarcoma treatment.

Positron emission tomography for response assessment in desmoplastic small round cell tumor

BACKGROUND

Desmoplastic small round cell tumors (DSRCT) typically have a large stromal component and often are extensively disseminated in the peritoneal cavity at diagnosis. These factors contribute to difficulty in quantifying response to chemotherapy using RECIST or WHO criteria. This study compares the overall disease response to chemotherapy by fluorodeoxyglucose-positron emission tomography (FDG-PET) and computed tomography (CT) in patients with DSRCT.

METHODS

We conducted a retrospective chart review of 7 patients with DSRCT who were imaged by FDG-PET and CT at diagnosis and after 3 cycles of chemotherapy. Response to chemotherapy was graded according to EORTC metabolic response guidelines and RECIST.

RESULTS

All tumors demonstrated some decrease in SUVmax (51%±21%) and longest diameter (23%±8%) with chemotherapy. The best response achieved by FDG-PET was a partial response in 6 patients and by CT was a partial response in 1 patient. Measured response was concordant between the 2 modalities in 2 patients.

CONCLUSIONS

In this small series response measurement by FDG-PET did not always correlate with response measurement by CT. A greater decrease in metabolic activity as compared with size was seen in all patients. Further studies are needed to define the role of FDG-PET in assessing early response of DSRCT to chemotherapy.

Comparison of PET-CT and conventional imaging in staging pediatric rhabdomyosarcoma

BACKGROUND

Over the past decade, PET-CT has been used to assess rhabdomyosarcoma (RMS) in children. However, the role of PET-CT in staging RMS is unknown.

PROCEDURE

Thirty subjects with RMS, median age 7.3 years, underwent PET-CT before therapy. PET-CTs and conventional imaging (CI) were independently reviewed by two radiologists and two nuclear medicine physicians to determine the presence of metastases. Accuracy, sensitivity, and specificity of PET-CT for detecting metastases were compared to CI using biopsy and clinical follow-up as reference standards. Maximum standardized uptake values (SUV(max)) of primary tumors, lymph nodes, and pulmonary nodules were measured.

RESULTS

Primary tumors had an average SUV(max) of 7.2 (range, 2.5-19.2). Accuracy rates for 17 subjects with nodal disease were 95% for PET-CT and 49% for CI. PET-CT had 94% sensitivity and 100% specificity for nodal disease. Of seven pulmonary nodules detected by CI, three were not identified by PET-CT, two were indeterminate, and one was malignant with a SUV(max) (3.4) > twice that of benign nodules. Two subjects had bone disease; both were identified by PET-CT but only one by CI. Four subjects had bone marrow disease, two had positive PET-CTs but none had positive CI. Two subjects had soft tissue metastases detected by PET-CT but not CI.

CONCLUSIONS

PET-CT performed better than CI in identifying nodal, bone, bone marrow, and soft tissue disease in children with RMS. CI remains essential for detection of pulmonary nodules. We recommend PET-CT for staging of children with RMS. CI with Tc(99m) bone scan can be eliminated.

(18) F-fluorodeoxyglucose positron emission tomography/computed tomography for the detection of recurrent bone and soft tissue sarcoma

BACKGROUND

The clinical utility of modern hybrid imaging modalities for detecting recurrent bone or soft tissue sarcoma remains to be determined. In this report, the authors present a clinical study on the diagnostic accuracy and incremental value of integrated (18) F-fluorodeoxyglucose positron emission tomography/computed tomography ((18) F-FDG PET/CT) in patients with a history of sarcoma who have clinically suspected disease recurrence.

METHODS

Forty-three patients who had a history of bone or soft tissue sarcoma and had documented complete remission underwent (18) F-FDG PET/CT. Image analysis was performed independently for (18) F-FDG PET (n = 43) and for contrast-enhanced spiral CT (CE-CT) (n = 30) by 2 separate readers, whereas combined (18) F-FDG PET/CT (n = 43) images were analyzed in consensus by both readers. Imaging findings were rated on a 5-point scale and finally were reported as malignant, benign, or equivocal. Imaging findings were validated either by histopathology (n = 24) or by clinical follow-up (n = 19).

RESULTS

(18) F-FDG PET/CT had greater sensitivity and specificity compared with CE-CT alone (94% and 92% vs 78% and 67%, respectively), resulting in significantly greater accuracy (93% vs 73%; P = .03). (18) F-FDG PET/CT was particularly superior regarding detection of local recurrence or soft tissue lesions (sensitivity and specificity: 83% and 100% vs 50% and 100%, respectively) or bone metastases (100% and 100% vs 85% and 88%, respectively).

CONCLUSIONS

(18) F-FDG PET/CT had greater diagnostic accuracy in the detection of recurrent bone or soft tissue sarcoma compared with CE-CT alone. The detection of local recurrence was the most evident advantage of (18) F-FDG PET/CT over CE-CT. Cancer 2013. © 2012 American Cancer Society.

Is there a need for dedicated bone imaging in addition to 18F-FDG PET/CT imaging in pediatric sarcoma patients?

PURPOSE

Many children with sarcomas undergo whole body 2-deoxy-2-((18)F)fluoro-D-glucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) and technetium methylene diphosphonate ((99)Tc-MDP) studies. It is unknown whether the combination of both tests results in more accurate detection of bone lesions than (18)F-FDG- PET/CT alone.

METHODS

(99)Tc-MDP bone and (18)F-FDG PET/CT scans were each read by 2 "blinded" observers and then reviewed side-by-side by 3 readers. Bone lesions were graded qualitatively on a 5-point scale (from benign to malignant). Clinical and imaging follow-up (n = 21) and bone biopsy results (n = 8) served as reference standard.

RESULTS

A total of 39 paired (99)Tc-MDP and (18)F-FDG-PET/CT studies (cases) performed at a mean interval 4 ± 7 days, were performed on 29 patients (mean age 12 ± 5 y). Of these, 21 patients (72%) had bone sarcoma, whereas 8 patients (28%) had soft tissue sarcoma. By patient and case-based analysis, (18)F-FDG PET/CT had an accuracy of 100%. Tc-MDP had accuracies of 90% and 82% by patient and case-based analysis. The combined interpretation had an accuracy of 97%.

CONCLUSIONS

In this study, (99)Tc-MDP bone imaging does not provide an added diagnostic value for bone involvement over (18)F-FDG-PET/CT.

Urogenital tumours in childhood

The commonest urogenital tumours in childhood are Wilms tumour of the kidney and rhabdomyosarcoma in the pelvis. We review these tumours along with other primary renal tumours and less common ovarian and testicular tumours in childhood. Current clinical concepts, relevant staging investigations and imaging features are described.

18F-fluorodeoxyglucose uptake of bone and soft tissue sarcomas in pediatric patients

A high (18)F-fluorodeoxyglucose (FDG) uptake by positron emission tomography/computed tomography (PET/CT) imaging in sarcomas of adults has been reported. The current study aimed at defining the degree of (18)F-FDG uptake of pediatric sarcomas. This retrospective study included 29 patients (23 males, 6 females; mean age 14 ± 5 years) with soft tissue (n = 9) or bone (n = 20) sarcomas. Twenty-two patients (76%) underwent (18)F-FDG PET/CT and 7 (24%) had dedicated (18)F-FDG PET studies. Tumor (18)F-FDG uptake was quantified by standard uptake value (SUV)(max) and tumor-to-liver ratios (SUV ratios; tumor SUV(max)/liver SUV(mean)). Tumor SUV(max) and SUV ratios were correlated with tumor Ki-67 expression. SUV(max) ranged from 1.4 to 24 g/mL (median 2.5 g/mL) in soft tissue sarcomas and 1.6 to 20.4 g/mL (median 6.9 g/mL) in bone sarcomas (P = .03), and from 1.6 to 9.2 g/mL (median 3.9 g/mL) and 3.5 to 20.4 g/mL (median 12 g/mL) in Ewing sarcoma and osteosarcoma, respectively (P = .009). Tumor SUV ratios ranged from 0.8 to 8.7 (median 1.9) in soft tissue sarcomas and 1.4 to 8.9 (median 3.8) in bone sarcomas (P = .08). Ewing sarcoma had a significantly lower tumor SUV ratio than osteosarcoma (P = .01). Ki-67 expression correlated significantly with the (18)F-FDG uptake in bone but not in soft tissue sarcomas. All sarcomas were visualized by (18)F-FDG PET/CT imaging. A higher (18)F-FDG uptake was observed in osteosarcoma than in Ewing and soft tissue sarcomas. The results of this study suggest that the degree of tumor (18)F-FDG uptake is sufficient to allow for monitoring of therapeutic responses in pediatric sarcomas.