Fluorodeoxyglucose positron emission tomography in the evaluation of germ cell tumours at relapse

Differentiation of active disease from fibrosis/mature teratoma in patients with residual masses or identifying of sites of recurrence in patients wit h raised markers following treatment of their testicular cancer remains a p roblem. F-18-fluorodeoxyglucose positron emission tomography (FDG-PET) has the potential to identify active disease and thereby influence further mana gement in these patients. We performed a retrospective study of the use of FDG-PET in detecting residual/recurrent testicular carcinoma in 55 patients (seventy FDG-PET scans). Forty-seven scans were for the assessment of resi dual masses (18 had raised markers) and 23 scans were for the investigation of raised markers in the presence of normal CT scans. True positive result s were based on positive histology or clinical follow-up. FDG-PET had a pos itive predictive value (PPV) of 96% and a negative predictive value (NPV) o f 90% in patients with residual masses. This PPV was equivalent to that of markers (94%) but FDG-PET had the advantage of identifying the site of that recurrence. The NPV was higher than that of markers. In patients with rais ed markers alone the PPV of FDG-PET was 92% but the NPV was only 50%. Howev er, subsequent FDG-PET imaging was frequently the first imaging modality to identify the site of disease. FDG-PET effected a management change in 57% of cases. FDG-PET scanning detected viable tumour in residual masses and id entified sites of disease in suspected recurrence. (C) 2000 Cancer Research Campaign.