[(18)F]FDG in childhood lymphoma: clinical utility and impact on management.

Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) is a very useful technique for the imaging of lymphomas in the adult population. It provides unique information about the behaviour of malignant cells and contributes to more accurate staging of the illness and better assessment of response to therapy. The purpose of this study was to evaluate the usefulness of FDG PET in childhood lymphoma compared with conventional imaging methods (CIMs) and clinical data. Between July 1998 and August 2001, 42 FDG PET examinations were performed using a dedicated PET system (27 examinations) or a hybrid coincidence PET system (15 examinations) for initial tumour staging ( n=7), restaging ( n=5) or assessment of response to therapy or residual masses ( n=30) in 27 children with Hodgkin's disease (HD) ( n=20) or non-Hodgkin's lymphoma (NHL) ( n=7). FDG PET results were compared with CIM findings and clinical data. Since 2000, a standardised questionnaire for evaluation of the clinical impact of FDG PET on both staging and therapy has been sent to the 16 referring physicians and 13 have replied. In all children, FDG PET was performed without any side-effects. FDG PET was found to be very sensitive (Se=12/12) for staging and restaging of the illness, showing more lesions than CIMs, with a 50% patient upstaging rate (6/12). It was very accurate for monitoring response to therapy and for characterisation of residual masses. False-positive results were observed in two NHL patients with thymic uptake and one false-negative result was obtained in a patient whose NHL relapsed 1 month after a negative FDG PET. The questionnaire emphasised the impact of FDG PET on clinical management, which was modified on the basis of the FDG PET results in 23% of patients. As previously demonstrated in the adult population, FDG PET appeared to be a very sensitive imaging technique for staging and restaging of lymphoma in children and was very useful for monitoring the response to therapy.