18F-FDG PET/CT in the evaluation of testicular nonseminomatous germ cell cancer after orchiectomy and chemotherapy

Objectives The role of 18F-FDG PET/CT in the assessment of post-chemotherapy nonseminomatous germ cell tumors is yet unclear. The aim of this study is to evaluate the role of 18F-FDG PET/CT in the assessment of testicular nonseminomatous germ cell tumors after orchiectomy and completing chemotherapy.

Methods Fifty-four scans of 18F-FDG PET/CT were performed in 40 patients (age range 19 to 54 years, average 31.1 ± 12.0 years) with testicular nonseminomatous germ cell tumors (embryonal carcinoma 11, malignant teratoma 7, yolk sac tumor 1, mixed germ cell tumor 21) after orchiectomy and chemotherapy. The 18F-FDG PET/CT results were validated by long-term clinical follow-up (range 8 to 65 months, median 28 months) and, in some patients, by the histopathology of the resected residual mass.

Results The accuracy of 18F-FDG PET/CT for the evaluation of residual tumor viability was 90.0% (36/40). Sensitivity and specificity were 94.1% (16/17) and 87.0% (20/23), respectively. In 3 patients with inflammation components and necrosis retroperitoneally after chemotherapy, the PET/CT results were falsely positive. In 1 patient with lung metastasis, the lung nodule (diameter 2.4 cm) failed to uptake 18F-FDG and presented falsely negative PET/CT. In 4 patients with residual cystic masses retroperitoneally, 18F-FDG PET/CT correctly predicted absence of viability in the residual masses. All 20 patients with true negative PET/CT had no evidence of relapse at a median follow up of 25 months.

Conclusions Our data suggest that 18F-FDG PET/CT could be useful to predict residual viability of nonseminomatous germ cell tumor after chemotherapy. Inflammatory treatment complications can lead to the falsely positive 18F-FDG PET/CT. A negative 18F-FDG PET/CT after chemotherapy may be a potential predictor of a favorable clinical outcome.