UC San Diego

Background

Standardized uptake values (SUVs) of fluorine-18 fluorodeoxyglucose PET ((18)F-FDG PET) are used widely to differentiate residual or recurrent high-grade gliomas from post-treatment changes in patients with brain tumors. The aim of this study is to assess the accuracy of SUV corrected by blood glucose level (SUV(gluc)) compared with various quantitative methods in this role.

Materials and methods

In 55 patients with dynamic F-FDG PET scans, there were 97 glioma lesions: glioblastoma (n=60), grade III gliomas (n=22), grade III or IV gliomas (n=6), grade I/II (n=7), and prebiopsy lesions (n=2). The final actual diagnosis was made on the basis of pathology (n=33) and clinical outcome (n=64). Dynamic F-FDG PET scans were processed to generate parametric images of SUV(gluc), SUV(max), and glucose metabolic rate (GMR). Lesion to cerebellum ratios (SUV(Rc)) and contralateral white matter ratios (SUV(Rw)) were also measured. The SUV(gluc) was calculated as SUV(max)×blood glucose level/100.

Results

Using the thresholds of SUV(max)>4.6, SUV(Rc)>0.9, SUV(Rw)>1.8, SUV(gluc)>4.3, and GMR>12.2 μmol/min/100 g to represent positivity for viable tumors, the accuracies were the same for the SUV(gluc) and SUV(Rw) (80%) and were higher than the conventional SUV(max) (72%). The area under the receiver operating characteristic curve for the SUV(gluc) (0.8933) was better than that for the SUV(max) (0.8266) (P<0.01) and was similar to those of the GMR (0.8622), SUV(Rc) (0.8606), and SUV(Rw) (0.8981).

Conclusion

These results suggest that SUV(gluc) may aid in the differentiation of residual or recurrent high-grade tumor from post-treatment changes in patients with abnormal blood glucose levels. The simplicity of the SUV(gluc) avoids the complexity of kinetic analysis or the requirement of a reference tissue.