Pilot study of F(18)-Fluorodeoxyglucose Positron Emission Tomography/computerised tomography in Wilms' tumour: correlation with conventional imaging, pathology and immunohistochemistry.

Wilms' tumour is the second most common paediatric solid tumour. Prognosis is good although higher stage disease carries significant mortality and treatment related morbidity. In the UK, risk stratification is based on histological response to pre-operative chemotherapy. F(18)-Fluorodeoxyglucose Positron Emission Tomography (F(18)FDG-PET) is an emerging functional imaging technique in paediatric oncology. Little is known about the relationship between F(18)FDG-PET images and the disease process of Wilms' tumour. We performed F(18)FDG-PET/CT scans in seven children with Wilms' tumour after induction chemotherapy, immediately before surgery. The standard uptake values (SUV) of F(18)FDG-PET/CT images were related to conventional imaging and histopathological findings. In total seven children were studied. F(18)FDG-PET/CT was consistently safely performed. All tumours showed F(18)FDG activity. Four tumours had activity with SUV/bw max >5 g/ml. Histological examination of these active areas revealed viable anaplastic Wilms' tumour. Furthermore, in these four tumours GLUT-1 and Ki67 immunostaining was strongly positive. Three further tumours demonstrated lower uptake (SUV/bw max <5 g/ml), which represented areas of microscopic foci of residual viable tumour mixed with post chemotherapy change. Metastatic disease was F(18)FDG avid in two of four children with stage four diseases. In conclusion, following chemotherapy, active Wilms' tumour is F(18)FDG avid and higher SUV was seen in histologically high risk disease.