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Ga-68 PSMA PET-CT in Staging Brain Tumors

Bright Awadh Sangiwa*12, Caroline Swai1 Frank Akida1, Baraka Fundo1 and Swaibu Ramadhani1

1Ocean Road Cancer Institute, Dar es salaam, Tanzania
2Department of Clinical Oncology, Muhimbili University of Health Allied Sciences (MUHAS), Dar es Salaam, Tanzania

*Corresponding author

*Akhil Mehrotra, Chief, Pediatric and Adult Cardiology, Prakash Heart Station, Nirala Nagar, Lucknow, UP, India

Abstract

PET molecular imaging has become a noble imaging modality with numerous tracers for different cancers. Ga-68 PSMA PET is a gold standard in imaging of prostate cancer as it is a prostate specific membrane antigen, however neovascular tumors including brain tumors have shown PSMA tracer avidity. Existing literature has reported the role of Ga-68 PSMA PET in diagnosis and early prognosis of brain tumors arising from glial cells. This case report illustrates role of Ga-PSMA PET in a 68‑year‑old female with high grade tumor (glioblastoma) confirmed by biopsy after a positive PSMA PET study.

Key words: Ga-68 PSMA-11, PSMA PET/CT, Glioblastoma

Introduction

Brain tumors (Gliomas) are tumors that can either be primary tumors, these originate in the brain or secondary/metastatic, these spread to the brain from tumors that originate elsewhere in the body. Primary tumors largely develop from glial cells which is the backbone structure of the brain supporting function
of neurons that control thought, sensation, muscle control and coordination [1]. The diagnosis of gliomas is by biopsy which determines the grade of the tumor, this is done through surgery or stereotactic needle biopsy (SNB). SNB is preferred when tumor is localized within critical area of the brain or when patient is very sick [2].
The gliomas are classified into benign (low grade gliomas, grade 1 and 2) and malignant (high grade gliomas, grade 3: anaplastic astrocytoma, anaplastic oligodendroglioma, anaplastic ependymoma, grade 4: glioblastoma). The higher the grade the poorer the prognosis. The treatment options for gliomas include surgery, radiotherapy, chemotherapy and electric fields [1].

The imaging modalities in glioma includes both anatomical imaging (CT and MRI) as well as molecular imaging (PET- CT/PET-MRI). Imaging contributes to the anatomical and molecular details of these tumors [3].

Description

68-year-old female with history of chronic general headache for 3 years, she reported to be taking natural herbs and at times anti-headache drugs which gave her relief. She recently reported worsen of her headache severely on the right side above the right ear for the past one month, on and off, aggravated by bending her head facing down. The pain was associated with numbness of her right side of the body (right side of the head, right lower and upper limbs), mild body weakness, difficulty in walking and mild loss of memory. No other clinical
symptoms were reported. She attended primary district hospital where she was diagnosed with high blood pressure and was kept on anti-hypertensive. CT brain was also performed and revealed ill-defined heterogeneous enhancing right temporo-parietal mass with surrounding massive vasogenic edema and mass
effect, provision diagnosis of high-grade glioma was made and MRI brain was recommended. The patient visited our institute for further work up and she was seen by the Oncologist and Nuclear Medicine Physician, further work up on imaging was ordered, MRI [Figure 2] and Ga-68 PSMA PET-CT [Figure 1]. The
Ga-68 PSMA PET-CT was ordered as a complimentary imaging, at time of imaging no other PET tracers were available.

Figure 1a: Axial PET (figure 1a) demonstrating intense PSMA circumferential uptake on the right side of the head, localizing to the right hemisphere on axial fused PET-CT image (figure 1b) with non- enhancing contrast axial CT (figure 1c) demonstrating an ill-defined hypo to iso-dense brain mass in right temporo-parietal region.

Figure 2: An irregular mass with vasogenic edema in the subcortical white matter of the right temporal lobe, measured about 6.3 x 4.6 x 4.5 cm, the mass appears hypo-intense in T1W (figure 2a), hyper to isointense in T2W (figure 2b) and showed irregular rim of enhancement in post contrast. Focal areas of signal voids were seen in hemo sequence (figure 2c), focal areas of restriction were also seen in ADC/DWI map, there was positive mass effect with midline shift by 1.0 cm to the contralateral side and partial effacement of the right lateral ventricle.

Discussion

Imaging modalities in brain tumors include both anatomical (CT /MRI) and molecular imaging (PET-CT/PET-MRI). When it comes to anatomical imaging, MRI is preferred over CT due to its ability in soft tissue description at staging as well as in evaluation of post treatment response differentiating between necrosis and viable residual tumor. However, CT still plays a primary role in brain imaging and provides complimentary information as well as is widely available [3]. Molecular imaging (PET-CT/PET-MRI) with different radiotracers have also shown to play a role in brain tumors both at staging and post treatment evaluation. PET scan at staging has ability to predict grading of the tumor from low grade (low tracer uptake) to high grade (intense tracer uptake) therefore may act as prognostic imaging. PET scan in post treatment evaluation of brain
tumors have as well demonstrated high diagnostic value in differentiation of post treatment necrosis (no tracer uptake) from viable residual tumor or disease progression (variable tracer uptake corresponding to metabolic activity of the viable tumor) [4].

Ga-68 PSMA PET, is a gold standard molecular imaging in prostate cancer, however the studies have shown its role in neovascular tumors including renal cell and brain tumors. Patients who are suspected of glial cells origin brain tumors, Ga-68 PSMA PET has shown to have a role in diagnosis and early prognosis of these tumors before surgery [5]. The patient had both MRI and Ga-68 PSMA PET at our institute. The Ga-68 PSMA PET-CT (Figure 1) showed intense PSMA circumferential uptake in the brain lesion, this lesion was also identified on MRI (Figure 2) with findings suggestive of a right temporal lobe brain tumor (Glioblastoma/Oligodendroglioma). The intensity of PSMA uptake was also highly suggestive of high grade brain tumor. The patient was then referred to neurosurgeon, she underwent surgery to debulk the tumor with final diagnosis of glioblastoma confirmed on biopsy.

In conclusion, our case report adds to literature on demonstration of the use of a-68 PSMA PET in patients who are suspected of high grade brain tumors, highlighting its great value in diagnosis and early prognosis of these tumors. In addition gallium based radiotracers need no patient preparation and can be performed in centers/ regions that do not have access to cyclotron based tracers.

Declaration of patient consent: The authors certify that they have obtained all appropriate patient consent
forms including consent for his images and other clinical information. The patient was guaranteed that his names and initials will not be disclosed.

Financial support and sponsorship
Nil.

Conflicts of interest
There are no conflicts of interest.

REFERENCES

  1. Ricardo J, Mc Faline-Figueroa, Eudocia Q Lee (2018) Brain Tumors. The American Journal of Medicine 131: 8.
  2. Matthew J, McGirt BS, Alan T Villavicencio, Ketan R Bulsara, Allan H Friedman (2003) MRI-guided stereotactic biopsy in the diagnosis of glioma: comparison of biopsy and surgical resection specimen. Surgical Neurology 59: 4.
  3. James R. Fink, Mark Muzi, Melinda Peck, Kenneth A Krohn (2015) Multimodality Brain Tumor Imaging: MR Imaging, PET, and PET/MR Imaging. Journal of Nuclear Medicine 56(10): 1554 1561.
  4. Giorgio Treglia, Barbara Muoio, Gianluca Trevisi (2019) Diagnostic Performance and Prognostic Value of PET/CT with Different Tracers for Brain Tumors: A Systematic Review of Published Meta-Analyses. Int J Mol Sci.
  5. Preoperative [68Ga] Ga-PSMA-11 PET/CT in patients with suspected brain tumors of glial origin – imply on diagnosis and early prognosis - a prospective clinical trial, Research Square 2025, Nuclear Medicine Department, Medical University of Warsaw.

JCMCRI
ISSN: 3064-8025

Journal of Clinical & Medical Case Reports, Images (JCMCRI) ISSN: 3064-8025 is a peer-reviewed journal dedicated to publishing clinical images from all sectors of medicine. The goal of this magazine is to disseminate information about new discoveries and treatments in science and medicine.

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