Can we rely on PET in the follow-up of advanced seminoma patients?

The management of residuals after completion of chemotherapy in advanced seminoma is controversial. It has been proposed that fluorodeoxyglucose-positron emission tomography (FDG-PET) can be used as a follow-up. In this study we investigated FDG-PET as a follow-up tool in advanced seminoma patients treated previously with chemotherapy or radiotherapy. Thirty-seven patients assigned to an advanced seminoma group based on CT and/or FDG-PET/CT and then treated with chemotherapy were included in the study. All these patients underwent FDG-PET/CT examination as a part of the follow-up scheme. Patients underwent retroperitoneal lymph node dissection (RPLND), radiotherapy, or were followed clinically by CT and/or PET/CT every 6 months. In 8 cases FDG-PET was positive: 5 of them underwent RPLND and 3 radiotherapy. Two patients with negative FDG-PET but positive CT also underwent RPLND. The remaining patients with negative FDG-PET results were followed up. FDG-PET/CT was false positive in one case >3 cm and one <3 cm, in 6 cases >3 cm it was true negative. While FDG-PET can find a viable tumor, there also is an important question of false positive results. It was clinically proven that a negative FDG-PET was correlated with stable disease, but we were unable to examine specimens in these cases.