Evaluation of intra-cranial germ cell tumors using 11C-methionine PET/CT

2000 Objectives Intra-cranial germ cell tumors is relatively rare brain tumors. There is no systematic study with 11 C-methionine (MET) PET on intra-cranial germ cell tumors so far. An aim of this study was to evaluate the usefulness of MET PET/CT comparing with 18 F-FDG PET/CT for diagnosis of intra-cranial germ cell tumors. Methods Subjects were 21 patients ( 20.4±12.1 years old, 2 females and 19 males ) with germinoma ( n=15 ), inmature teratoma ( n=3 ) and york sac tumor ( n=3 ) before therapy. Both 11 C-MET and 18F-FDG PET/CT using dedicated PET/CT scanners ( Biograph s6 or s16, Siemens ) underwent before surgical biopsy. Ten patients were obtained follow-up studies after therapy. SUVmax MET and FDG were calculated and obtained from voxels of interests drawn manually. Results MET-SUVmax of all intra-cranial germ cell tumors was 2.79±1.26. FDG imaging of germinoma was 3 positive and 18 negative. The MET uptake in the lesions after therapy was faint and MET-SUVmax in the same regions of all ten patients was 1.54±0.39 ( range 1.06 - 2.18 ). There was a significance between SUVmax before and after therapy ( p Conclusions 11 C-MET PET/CT was useful to detect intra-cranial germ cell tumors before therapy although the MET uptake in the 9 patients was faint. In the cases with the high MET uptake in the lesions, the MET uptake may be a good marker of tumor activity and residual lesions. FDG PET/CT was less useful because germ cell tumors showed less FDG uptake compared with cerebral physiological uptake in most cases.