Positron emission tomography in germ cell tumors in men:Possibilities and limitations,Positronenemissionstomographie bei Keimzelltumoren des Mannes: Einsatzmöglichkeiten und Grenzen

BACKGROUND: Conventional radiographic imaging may fail to safely distinguish clinical stage I from stage IIA germ cell cancer, to localize isolated tumor marker relapses, and to equivocally identify the viability of postchemotherapy residual masses.

OBJECTIVES: To provide an overview of the diagnostic value and limitations of functional imaging by positron emission tomography with 2‑deoxy-2-[fluorine-18]fluoro-D-glucose with computed tomography (18F-FDG-PET-CT) in male germ cell cancer.

MATERIALS AND METHODS: A narrative review based on a literature search of PubMed/MEDLINE for original articles published from 1990-2018 and conference proceedings of ASCO (American Society of Clinical Oncology) and EAU (European Association of Urology) annual meetings 2014-2017 is presented.

RESULTS: 18F-FDG-PET-CT does not improve diagnostic accuracy compared to conventional CT imaging clinical stage (CS) I disease. Particularly PET-negativity of postchemotherapy residual masses of seminomas >3 cm in size guide decision-making against further additional treatment. Even PET-positive residues must not result in relapse. For nonseminoma, the value of PET imaging is reduced by potential mature teratoma components, which are commonly PET negative.

CONCLUSIONS: Current guidelines recommend 18F-FDG-PET-CT 6-8 weeks postchemotherapy for viability assessment of seminoma residues >3 cm in size. Exceptional circumstances, in which 18F-FDG-PET-CT may be helpful, include: (1) detection of active disease in CS IS, (2) viability assessment of residual masses >1 cm where complete secondary resection is impossible, (3) staging at marker relapse with unconspicuous conventional CT scan, (4) early response assessment during chemotherapy.