The influence of blood glucose levels on [18F]fluorodeoxyglucose (FDG) uptake in cancer: a PET study in liver metastases from colorectal carcinomas.
OBJECTIVE
To study the influence of blood glucose levels on the clinical reliability of positron emission tomography (PET) with [18F]-2-fluoro-2-deoxy-D-glucose (FDG) in the detection of liver metastases from colorectal carcinomas and in the analysis of tumor uptake of FDG.


METHODS
After having given their informed consent, 8 patients with 20 liver metastases (mean size, 31.5 mm; range, 10-75 mm) detected by means of CT were submitted to a first FDG-PET examination under fasting conditions and, 2 days later, to a second FDG-PET examination performed after i.v. infusion of a glucose solution (4 mg/kg/min for 2 hrs). The results of the two studies were compared in each patient, considering both the localization of the metastases and the FDG uptake in the lesions. A non-kinetic method was used, calculating the Standardized Uptake Value (SUV).


RESULTS
All 20 metastases were clearly visible on FDG-PET under fasting conditions. Moreover, in 2 patients FDG-PET detected a number of unknown liver metastases. The blood glucose levels after glucose infusion were significantly higher than the levels under fasting conditions, 158 +/- 13.8 mg/100 ml (mean +/- sd) and 92.4 +/- 10.2, respectively (P < 0.001), and the quality of the FDG-PET images showed a marked deterioration. FDG-PET was unable to detect 6 of the 20 lesions and another 10 lesions were localized less clearly. Moreover, 80% of the unknown liver metastases were not detected after glucose loading. The SUVs of metastases decreased from 9.4 +/- 5.7 (mean +/- sd) under fasting conditions to 4.3 +/- 8.3 after glucose loading (P < 0.001).


CONCLUSIONS
FDG-PET studies may be particularly unreliable under conditions of high levels of blood glucose. Therefore, patients entering FDG-PET studies should fast, and blood glucose concentration needs to be taken into account when evaluating FDG uptakes in follow-up studies.
Crippa
F
F
PET Unit, National Cancer Institute, Milan, Italy.
Gavazzi
C
C
Bozzetti
F
F
Chiesa
C
C
Pascali
C
C
Bogni
A
A
De Sanctis
V
V
Decise
D
D
Schiavini
M
M
Cucchetti
G
G
Bombardieri
E
E
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D015179:Colorectal Neoplasms / Q000473:pathology*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging* / Q000378:metabolism*; D008113:Liver Neoplasms / Q000097:blood / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000556:secondary; D008297:Male; D008875:Middle Aged; D014055:Tomography, Emission-Computed
D001786:Blood Glucose; D019788:Fluorodeoxyglucose F18