⁶⁸Ga-PSMA PET/CT in a case of recurrent Glioblastoma

Introduction

A 57-year-old man diagnosed with left frontal lobe glioblastoma multiforme IDH wild-type grade IV was operated on in June 2023. He received concurrent chemoradiotherapy with Temozolomide and received 60 Gy in 20 fractions in August 2023. He then developed complaints of headaches 6 months postsurgery, and had recurrent disease on MRI. He was referred for positron emission tomography/computed tomography (PET/CT) with a theranostic intent.

Maximum intensity projection image of the whole body (A, green arrow) and brain (C) shows increased metabolism in the left frontal lobe. PET images (B) show hypermetabolism in the left frontal region. CT and ⁶⁸Ga PSMA 11 PET/CT scan (D and E, axial CT and fused PET/CT; F and G, coronal CT and fused PET/CT) shows intense tracer uptake along the periphery of an irregular hypodense lesion in the left frontal lobe [Figure 1]. MR images showed a heterogeneously hyper-intense area of altered signal intensity in the left frontal lobe, with a postcontrast study showing a peripheral patchy enhancement. Due to the absence of normal physiological ⁶⁸Ga PSMA 11 PET/CT uptake in the brain parenchyma, the lesion showed clear margins, which can be made out in ⁶⁸Ga PSMA 11 PET/CT images with SUV_max of 4.08.

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Figure 1 Maximum intensity projection image of the whole body ([a] green arrow) and brain (c) shows increased metabolism in the left frontal lobe. Positron emission tomography (PET) images [b – orange arrow] show hypermetabolism in the left frontal region. Computed tomography (CT) and ⁶⁸Ga PSMA 11 PET/ CT scan ([d and e], axial CT and fused PET/CT; [f and g – green arrow], coronal CT and fused PET/CT) shows intense tracer uptake along the periphery of an irregular hypodense lesion in the left frontal lobe

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Discussion

Glioblastoma is the most common and most aggressive primary tumor of the brain with a poor prognosis and median survival of approximately 14–15 months from diagnosis with a high recurrence rate.[1] Gadolinium-enhanced MRI is the imaging modality of choice for recurrence, but it’s difficult to differentiate between radiation necrosis and recurrence. The prospective role of ⁶⁸Ga PSMA 11 PET/CT brain imaging in high-grade gliomas has been assessed in various studies and found to be very useful in the evaluation of glioma recurrence.[23] Unlike 18F-FDG PET/CT, which has high physiological uptake in the brain parenchyma, ⁶⁸Ga PSMA 11 has no physiologic tracer uptake in the normal brain parenchyma, which helps in tumor delineation. From a theranostic perspective, the lesion uptake was equal to or slightly more than the liver.[4] The findings of our case underscore the utility of ⁶⁸Ga PSMA 11 PET/CT imaging of suspected glioblastoma recurrence cases and for potential theranostic applications using alpha or beta emitters.[5]