Metabolic changes of glioma following chemotherapy: an experimental study using four PET tracers

To shed light on the metabolic changes in glioma following therapy, uptake changes among 18F-fluoro-2'-deoxyuridine (18FUdR), 14C-thymidine (dThd), 14C-methionine (Met) and 3H-deoxyglucose (DG) in glioma model after chemotherapy were studied, as a means for interpreting clinical PET results, together with the changes in the bromodeoxyuridine (BUdR) labeling index. 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(-2chloroethyl)-3-nitro sourea hydrochloride (ACNU) was administered intraperitoneally in the tumor-bearing rats and uptake of the tracers or BUdR labeling index in tumor tissue were measured. The metabolic response following chemotherapy was a sharp fall immediately for 14C-dThd and 18FUdR and a moderate fall for 14C-Met whereas there was a fall in 3H-DG from 1 week after chemotherapy. The changes of BUdR labeling index paralleled that in the uptake for dThd and FUdR. These result indicate that PET scans using a variety of tracers in conjunction could be used for clinical diagnosis and evaluation of therapy in glioma cases. 18FUdR is a promising tracer of nucleic acid metabolism to evaluate the proliferative potential of brain gliomas.