Brainstem Glioma Prognostication: Static FET PET/CT.

Background/objectives: The classification and staging of brainstem glioma have its own pitfalls. Surgical biopsy is only possible in a small number of cases. Diagnosis relies mainly on radiological features. Any treatment may have a significant impact on quality of life; therefore, the correct and early identification of potentially malignant lesions is essential to initiate proper therapy. Amino acid PET/CT with accurate metabolic mapping can help in this decision-making.

Methods: We performed a retrospective analysis of 20 patients who underwent static FET PET/CT with uncertain brainstem lesions between November 2019 and April 2023. We used multiple tumor-to-brain ratios (TBR) to assess patient subgroups showing long-term and short-term survival.

Results: The maximum Youden index was reached at TBR = 2.9. With this ratio, the estimated sensitivity was at the desired level (91.7%), both positive and negative predictive values are in the good performance range (68.8 and 75.0%), while specificity was lower than expected (37.5%).

Conclusions: The prognosis of brainstem glioma remains challenging. The use of static FET PET/CT results in more accurate detection of high-grade lesions. In our analysis, we found a TBR value of 2.9 to be the most appropriate for identifying patients with a poor prognosis.