Abstract
1714
Objectives Hyperglycemia negatively impacts FDG-PET/CT scanning by direct competition between glucose in the blood and FDG for uptake into tumor cells. Suggested cut-off points of blood glucose levels (BGL) prior to FDG-PET/CT scanning vary between 120-200 mg/dL in current available guidelines. The purpose of this study was to compare the frequency of abnormal FDG biodistribution on PET/CT scans of patients with various ranges of abnormal BGL.
Methods This retrospective study was IRB-approved. 4,582 FDG-PET/CT scans were performed from 7/14 to 9/15 for oncology indications. BGL were > 120 mg/dL at the time of scan in 555 scans. 63 patients had multiple scans, and only the first was used for further analysis. The control group consisted of 111 randomly selected patients during the same timeframe with BGL ≤120 mg/dL. FDG biodistribution was categorized as normal, mildly abnormal, or abnormal by visual analysis of brain, background soft tissue and muscle. Mean standardized uptake values (SUVmean) in brain, liver, fat (flank), gluteal muscle, blood pool (aorta) were recorded. FDG biodistribution frequencies were compared using Chi-squared trend test. Normal organ SUVs were compared using Kruskal-Wallis tests using the following BGL groupings: ≤120, 121-150, 151-200, 蠅201 mg/dL.
Results Table 1 shows the results of the visual assessment of FDG biodistrubiton. Although higher BGL were significantly associated with an increased proportion of abnormal biodistribution (p<0.001), the majority of patients with BGL≤200 mg/dL had normal or mildly abnormal biodistribution. Normal organ SUVmean categorized by BGL are shown in Table 2. Average brain SUVmean significantly decreased with higher BGL (p120 mg/dL (p=0.69, 0.89, 0.52, respectively), but were significantly lower in those with BGL≤120 mg/dL (p≤0.001). Flank fat SUVmean was not significantly different among BGL groups (p=0.83).
Conclusions Abnormal FDG biodistribution is associated with higher BGL at the time of scan, but the effects seem either negligible or mild in the majority of patients with BGL< 200 mg/dL. While mildly increased soft tissue uptake is seen with BGL> 120 mg/dL, decline in metabolic activity in the brain was the only finding that correlates most with various BGL. Relative metabolic activity in the brain could be useful for quality control of scans and for assessing potential impact on interpretation when practical logistics necessitate scanning in patients with high or difficult to control BGL.