CLINICAL HISTORY
A 37-year-old female with diagnosis of high-grade glioma in 2015. She had surgical resection followed by concurrent chemoradiotherapy with 60Gy/30# from 9/6/2015 to 28/07/2015. Adjuvant temozolomide on 31/08/2015 completed 6 cycles in February 2016. However, a recent MRI done in December 2022 suggestive of necrosis rather than recurrence.
IMAGING:
FDG PET/CT show hypermetabolic lesion is seen at the right temporal region with SUV max 16.9 (reference gray matter activity is SUV max 10.2). Another small focal area of increase FDG uptake of SUV max 10.6 is seen in the insular region. Findings are consistent with recurrence.
MRI brain: A heterogeneous signal intensity region is seen at right temporo-parietal cortex. The region is hypointense to gray matter on T1 and hyperintense on T2 and FLAIR imaging. Findings favor suggestive of necrosis rather than recurrence.
LEARNING POINTS:
18F-FDG PET/CT is valuable in the evaluation of high-grade gliomas (HGGs), it is often used in conjunction with other imaging modalities and clinical assessments to provide a comprehensive evaluation and guide patient management. 18F-FDG PET imaging may not provide significant additional information beyond what can be obtained from MRI and other imaging studies.
However, 18F-FDG PET/CT may be useful in specific situations such as:
1. Distinguishing between tumor recurrence and treatment-related changes: It is often difficult to differentiate between tumor recurrence and treatment-related changes such as radiation necrosis or inflammation on MRI alone. 18F-FDG PET/CT can help to identify areas of increased metabolic activity and thus help differentiate between these two entities.
2. Grading and Characterization: 18F-FDG PET/CT scan helps in differentiating high-grade gliomas from low-grade gliomas by assessing the metabolic activity of the tumor. High-grade gliomas generally exhibit increased glucose.
3. Identifying distant metastases: HGGs can metastasize outside of the brain, and 18F-FDG PET/CT can be useful in detecting distant metastases, especially in cases where there is a high suspicion of extracranial spread.
4. Evaluating treatment response: 18F-FDG PET/CT can be used to monitor treatment response in HGGs by measuring changes in metabolic activity.
5. Prognostic Information: 18F-FDG PET/CT provide valuable prognostic information that aids in predicting patient outcomes and guiding treatment decisions. Higher FDG uptake in gliomas has been correlated with worse outcomes and shorter survival rates.
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