L-[1-carbon-11]tyrosine imaging of metastatic testicular nonseminoma germ-cell tumors

The aim of this study was to investigate whether PET with L-[1-C-11]tyrosine (TYR) can be used to visualize metastatic disease of nonseminoma testicular germ-cell tumors and to monitor the effect of systemic cisplatinum-based polychemotherapy in a noninvasive fashion to reduce the number of operations in patients with a residual retroperitoneal tumor mass. Methods: Ten patients with retroperitoneal nonseminoma testicular germ-cell tumors metastases were studied with TYR PET before the start of cisplatinum-based polychemotherapy. A dose of 370 MBq of TYR was injected intravenously, and a 30-min TYR image was acquired 20 min after injection. The standardized uptake value of TYR was calculated in visualized lesions. Results: PET showed increased focal uptake of TYR in the retroperitoneum of 2 patients (20%). In 2 patients with large and inhomogeneous lesions on CT, PET showed decreased TYR uptake at the site of the lesion (20%). In the other 6 patients, the metastatic tumor masses were not depicted (60%). Because of these disappointing results, no posttreatment scans were obtained. Standardized uptake values of the visualized lesions varied from 1.05 to 2.87 for the lesions with increased metabolism and from 0.29 to 0.34 for lesions with decreased metabolism. Conclusion: PET with TYR is not suited to visualize the apparently slowly proliferating nonseminoma testicular germ-cell tumors or determine the nature of a residual retroperitoneal mass after chemotherapy.