[18F]-FDG–PET in clinical stage I/II non-seminomatous germ cell tumours: results of the German multicentre trial

The aim of this study was to determine the predictive values of 2-[fluorine-18]fluoro-2-deoxy-D-glucose–positron emission tomography (FDG–PET) in primary staging in patients with newly diagnosed non-seminomatous germ cell tumour (NSGCT) clinical stage I/II. The hypothesis was that FDG–PET would improve the negative predictive value (NPV) from 70% to 90%, thus requiring a total of 169 patients. All scans underwent visual analysis by a reference team of nuclear medicine physicians. Results were validated by histology following retroperitoneal lymph node dissection. Only 72 of the planned 169 patients were included, due to poor accrual. The prevalence of nodal involvement was 26%. Correct nodal staging by FDG–PET was achieved in 83% compared with correct computed tomography (CT) staging in 71%. CT had a sensitivity and specificity of 41% and 95%, respectively. Positive predictive value (PPV) and NPV were 87% and 67%, respectively. FDG–PET had a sensitivity and specificity of 66% and 98%, respectively. PPV was 95%. The primary end point was not reached, with an NPV of 78%. FDG–PET as a primary staging tool for NSGCT yielded only slightly better results than CT. Both methods had a high specificity while false-negative findings were more frequent with CT. FDG–PET is mostly useful as a diagnostic tool in case of questionable CT scan.