Assessment of response to treatment in paediatric bone sarcomas by means of PET imaging

The present review focuses on the current literature about the role of positron emission tomography (PET) imaging in the evaluation of response to treatment in patients with bone sarcomas. Osteosarcoma and Ewing sarcoma are the most frequent primary bone tumours occurring in the paediatric age. Imaging methods are attractive since they offer a non-invasive approach to evaluate response to treatment and are of particular interest in those patients with non-resectable tumours, for whom full histological assessment cannot be obtained. While conventional radiologic imaging can only assess the occurrence of structural changes in malignant tumours, molecular imaging by means of 18F-fluoro-2-deoxyglucose positron emission tomography/computed tomography ([18F]FDG–PET/CT) provides useful information about tumour metabolism, which is more likely to reflect response to treatment. As metabolic changes occur early during the treatment, an earlier assessment of tumour response may be feasible by means of [18F]FDG–PET/CT than using conventional imaging. As such, [18F]FDG–PET/CT may provide useful information for prognosis and clinical management of sarcoma patients. In contrast to OS, there is still some uncertainty in ES patients as to whether a massive SUVmax reduction in FDG–PET correlates with good histopathological response, despite a strong reduction of FDG uptake after the completion of neoadjuvant treatment.