Quantitative FET-PET makes the grade for advanced glioma

High-grade astrocytoma is a particularly aggressive form of glioma. Parameters of PET imaging such as the minimal time-to-peak could help clinicians narrow in on the best line of treatment for each patient, according to a study published Dec. 23 in the Journal of Nuclear Medicine.

Astrocytic gliomas often come with a very dismal prognosis, despite recent innovations in diagnosis and therapy. Applying the imaging agent F-18 fluoro-ethyl-tyrosine (FET) could strengthen the prognostic value of PET.  

Nathalie L. Jansen, MD, from the department of nuclear medicine at Ludwig-Maximilians-University in Munich, Germany, and colleagues evaluated 121 patients with primary astrocytic high-grade glioma by measuring the time-activity curve known as minimal time-to-peak, as well as tumor uptake and volume with FET PET.

“One of the most promising radiotracers is [FET], which shows high uptake in glioma cells and low uptake in healthy brain tissue, resulting in an excellent tumor-to-background-contrast,” wrote Jansen et al. “In this context, especially dynamic acquisition of [FET-PET] has gained increasing interest, as it enables glioma characterization by differentiating between low and high grade glioma tissue by analysis of individual time-activity-curves of [FET]-uptake.”

The researchers fused PET and MR scans together to assess glioma grade and confirmed their findings with histological testing. Results of the study showed that minimal time-to-peak provided the most prognostic information out of the set of PET parameters. Specifically, minimal time-to-peak was correlated with poor outcomes for recently diagnosed subjects with astrocytic high-grade glioma and could be comparable to the traditional World Health Organization (WHO) 1-4 grading system.

“Additionally, [time-to-peak minimum] can help identify highly aggressive tumors among WHO III degree astrocytoma and might help adjusting standard treatment towards an individualized, risk-adapted therapy regime,” the researchers wrote.

The median progression-free survival (PFS) and overall survival (OS) for study participants was 12.2 and 21.9 months, respectively. Those who were classified as having WHO III degree tumors experienced significantly longer PFS than patients deemed to have glioblastoma multiforme (GBM), 46.2 months vs. 14.2 months. This also was the case for OS, 19.3 months vs. 10.3 months. However, PET minimal time-to-peak was able to pick out WHO III degree subjects who would not end up fairing any better than those with GBM.