The influence of blood glucose levels on [18F]fluorodeoxyglucose (FDG) uptake in cancer: a PET study in liver metastases from colorectal carcinomas

Tumori. 1997 Jul-Aug;83(4):748-52. doi: 10.1177/030089169708300407.


Aims and background: 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.

MeSH terms

  • Adult
  • Blood Glucose / metabolism*
  • Colorectal Neoplasms / pathology*
  • Female
  • Fluorodeoxyglucose F18 / metabolism*
  • Humans
  • Liver / diagnostic imaging*
  • Liver / metabolism*
  • Liver Neoplasms / blood
  • Liver Neoplasms / diagnostic imaging*
  • Liver Neoplasms / metabolism*
  • Liver Neoplasms / secondary
  • Male
  • Middle Aged
  • Tomography, Emission-Computed*


  • Blood Glucose
  • Fluorodeoxyglucose F18