Germ cell tumor: differentiation of viable tumor, mature teratoma, and necrotic tissue with FDG PET and kinetic modeling.
OBJECTIVE
To evaluate the feasibility of positron emission tomography (PET) with 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) in patients with germ cell tumor (GCT) to monitor treatment and differentiate residual masses after chemotherapy.


METHODS
Twenty-six FDG PET studies were performed in 21 patients with GCT, FDG uptake of tumors was interpreted visually, and the lean standardized uptake value (SUVlean) was determined. Tumor kinetic rate constants (K1, k2, k3) and net rate of FDG phosphorylation (K = [K1.k3]/[k2 + k3]) in tumors were calculated from the dynamic data by means of a three-compartment model, assuming k4 = 0.


RESULTS
Viable tumors (n = 10) showed intense FDG uptake and could easily be differentiated visually from mature teratoma (n = 6) and necrosis or scar (n = 10). The SUVlean of residual viable tumors (4.51 +/- 1.34 [mean +/- SD]) was higher than that of mature teratoma (1.38 +/- 0.71) and necrosis or scar (1.05 +/- 0.29) (P < .05). Although neither the visual interpretation nor SUVlean differentiated mature teratoma from necrosis or scar, there were statistically significant differences in the kinetic rate constants K1 and K between mature teratoma and necrosis or scar as follows: K1, 0.113 mL/min/g +/- 0.026 versus 0.036 mL/min/g +/- 0.005 (P < .05); K, 0.005 mL/min/g +/- 0.003 versus 0.0008 mL/min/g +/- 0.0001 (P < .05).


CONCLUSIONS
FDG PET with kinetic analysis appears to be a promising method for management of disease in patients with GCT after treatment.
Sugawara
Y
Y
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109-0028, USA.
Zasadny
K R
KR
Grossman
H B
HB
Francis
I R
IR
Clarke
M F
MF
Wahl
R L
RL
D000328:Adult; D003937:Diagnosis, Differential; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D018237:Germinoma / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000556:secondary; D006801:Humans; D008297:Male; D008954:Models, Biological; D009336:Necrosis; D018365:Neoplasm, Residual; D019275:Radiopharmaceuticals; D012186:Retroperitoneal Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary; D013724:Teratoma / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000556:secondary; D014055:Tomography, Emission-Computed
D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18