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Purpose: The objective of this study was to evaluate positron emission tomography (PET) using F-fluoro-2-deoxy- D-glucose (FDG) in comparison to volumetry and standardized magnetic resonance imaging (MRI) parameters for the assessment of histological response in paediatric bone sarcoma patients. Methods: FDG PET and local MRI were performed in 27 paediatric sarcoma patients [Ewing sarcoma family of tumours (EWS), n = 16; osteosarcoma (OS), n = 11] prior to and after neoadjuvant chemotherapy before local tumour resection. Several parameters for assessment of response of the primary tumour to therapy by FDG PET and MRI were evaluated and compared with histopathological regression of the resected tumour as defined by Salzer-Kuntschik. Results: FDG PET significantly discriminated responders from non-responders using the standardized uptake value (SUV) reduction and the absolute post-therapeutic SUV (SUV2) in the entire patient population (∆SUV, p = 0.005; SUV2, p = 0.011) as well as in the subgroup of OS patients (∆SUV, p = 0.009; SUV2, p = 0.028), but not in the EWS subgroup. The volume reduction measured by MRI/CT did not significantly discriminate responders from non-responders either in the entire population ( p = 0.170) or in both subgroups (EWS, p = 0.950; OS, p = 1.000). The other MRI parameters alone or in combination were unreliable and did not improve the results. Comparing diagnostic parameters of FDG PET and local MRI, metabolic imaging showed high superiority in the subgroup of OS patients, while similar results were observed in the population of EWS. Conclusion: FDG PET appears to be a useful tool for non-invasive response assessment in the group of OS patients and is superior to MRI. In EWS patients, however, neither FDG PET nor volumetry or standardized MRI criteria enabled a reliable response assessment to be made after neoadjuvant treatment. [ABSTRACT FROM AUTHOR]

This prospective single-centre phase II trial assessed the diagnostic impact of 18F-FDG PET–CT in the evaluation of solid pancreatic lesions (∅ ≥10 mm) compared to endosonography (EUS), endoscopic retrograde cholangio-pancreatography (ERCP) with intraductal ultrasound (IDUS), abdominal ultrasound (US) and histopathological reference. Forty-six patients (32 men/14 women, ∅ 61.7 years) with suspected pancreatic neoplasms underwent PET–CT with contrast-enhanced biphasic multi-detector CT of the upper abdomen followed by a diagnostic work-up with EUS, ERCP with IDUS and US within 3 weeks. PET–CT data sets were analysed by two expert readers in a consensus reading. Histology from surgery, biopsy/fine-needle aspiration and/or clinical follow-up ≥12 months served as standard of reference. Twenty-seven pancreatic malignancies were histopathologically proven; 19 patients had benign diseases: 36/46 lesions (78%) were detected in the head of the pancreas, 7/46 and 3/46 in the body and tail region, respectively. Sensitivity and specificity of PET–CT were 89% and 74%, respectively; positive predictive value (PPV) and negative predictive value (NPV) were 83% and 82%, respectively. Sensitivity (81–89%), specificity (74–88%), PPV (83–90%) and NPV (77–82%) achieved by EUS, ERCP and US were not significantly different. PET analysis revealed significantly higher maximum mean standardised uptake values (SUVmax 6.5 ± 4.6) in patients with pancreatic malignancy (benign lesions: SUVmax 4.2 ± 1.5; p < 0.05). PET–CT revealed cervical lymphonodal metastasis from occult bronchogenic carcinoma and a tubular colon adenoma with intermediate dysplasia on polypectomy, respectively. 18F-FDG PET–CT achieves a comparably high diagnostic impact evaluating small solid pancreatic lesions versus conventional reference imaging modalities. Additional clinical diagnoses are derived from concomitant whole-body PET–CT imaging. [ABSTRACT FROM AUTHOR]

As primary osseous metastasis is the main adverse prognostic factor in patients with Ewing tumours, a NOD/ scid mouse model for human Ewing tumour metastases has been established to examine the mechanisms of metastasis. The aim of this study was to evaluate the feasibility of diagnostic molecular imaging by small animal PET in this mouse model. Human Ewing tumour cells were transplanted into immune-deficient NOD/ scid mice via s.c injection ( n=17) or i.v. injection ( n=17). The animals (mean weight 23.2 g) were studied 2–7 weeks after transplantation using a submillimetre resolution animal PET scanner. To assess glucose utilisation and bone metabolism, mice were scanned after intravenous injection of 9.6 MBq (mean) 2-[18F]fluoro-2-deoxy- D-glucose (FDG) or 9.4 MBq (mean) [18F]fluoride. Whole-body PET images were analysed visually and semi-quantitatively [%ID/g, tumour to non-tumour ratio (T/NT)]. Foci of pathological uptake were identified with respect to the physiological organ uptake in corresponding regions. Subcutaneously transplanted Ewing tumours demonstrated a moderately increased glucose uptake (median %ID/g 2.5; median T/NT 2.2). After i.v. transplantation, the pattern of metastasis was similar to that in patients with metastases in lung, bone and soft tissue. These metastases showed an increased FDG uptake (median %ID/g 3.6; median T/NT 2.7). Osseous metastases were additionally visible on [18F]fluoride PET by virtue of decreased [18F]fluoride uptake (osteolysis; median %ID/g 8.4; median T/NT 0.59). Metastases were confirmed immunohistologically. Diagnostic molecular imaging of Ewing tumours and their small metastases in an in vivo NOD/ scid mouse model is feasible using a submillimetre resolution PET scanner. [ABSTRACT FROM AUTHOR]

The article inquires on whether positron emission tomography/computed tomography(PET/CT) is necessary in pediatric oncology. It advocates that PET/CT will improve the accuracy of staging and will carry the potential to change management in a number of pediatric patients. It suggests that well-designed prospective study on the subject is needed in order to improve diagnosis and treatment of cancer in children.