PET tracers in glioblastoma: Toward neurotheranostics as an individualized medicine approach

Clinical Theranostics in Recurrent Gliomas: A Review

Gliomas represent the most commonly occurring tumors in the central nervous system and account for approximately 80% of all malignant primary brain tumors. With a high malignancy and recurrence risk, the prognosis of high-grade gliomas is poor, with a mean survival time of 12-18 months. While contrast-enhanced MRI serves as the standard diagnostic imaging modality for gliomas, it faces limitations in the evaluation of recurrent gliomas, failing to distinguish between treatment-related changes and tumor progression, and offers no direct therapeutic options. Recent advances in imaging modalities have attempted to address some of these limitations, including positron emission tomography (PET), which has demonstrated success in delineating tumor margins and guiding the treatment of recurrent gliomas. Additionally, with the advent of theranostics in nuclear medicine, PET tracers, when combined with therapeutic agents, have also evolved beyond a purely diagnostic modality, serving both diagnostic and therapeutic roles. This review will discuss the growing involvement of theranostics in diagnosing and treating recurrent gliomas and address the associated impact on quality of life and functional recovery.

Glioblastoma Therapy: Past, Present and Future

Glioblastoma (GB) stands out as the most prevalent and lethal form of brain cancer. Although great efforts have been made by clinicians and researchers, no significant improvement in survival has been achieved since the Stupp protocol became the standard of care (SOC) in 2005. Despite multimodality treatments, recurrence is almost universal with survival rates under 2 years after diagnosis. Here, we discuss the recent progress in our understanding of GB pathophysiology, in particular, the importance of glioma stem cells (GSCs), the tumor microenvironment conditions, and epigenetic mechanisms involved in GB growth, aggressiveness and recurrence. The discussion on therapeutic strategies first covers the SOC treatment and targeted therapies that have been shown to interfere with different signaling pathways (pRB/CDK4/RB1/P16ink4, TP53/MDM2/P14arf, PI3k/Akt-PTEN, RAS/RAF/MEK, PARP) involved in GB tumorigenesis, pathophysiology, and treatment resistance acquisition. Below, we analyze several immunotherapeutic approaches (i.e., checkpoint inhibitors, vaccines, CAR-modified NK or T cells, oncolytic virotherapy) that have been used in an attempt to enhance the immune response against GB, and thereby avoid recidivism or increase survival of GB patients. Finally, we present treatment attempts made using nanotherapies (nanometric structures having active anti-GB agents such as antibodies, chemotherapeutic/anti-angiogenic drugs or sensitizers, radionuclides, and molecules that target GB cellular receptors or open the blood-brain barrier) and non-ionizing energies (laser interstitial thermal therapy, high/low intensity focused ultrasounds, photodynamic/sonodynamic therapies and electroporation). The aim of this review is to discuss the advances and limitations of the current therapies and to present novel approaches that are under development or following clinical trials.

[177Lu]Lu-DOTAGA.Glu.(FAPi)2 Radionuclide Therapy: a New Treatment Option for Patients with Glioblastoma Multiforme

In this case report, we present the clinical management of a 52-year-old female patient with a recurrent right temporo-parietal glioblastoma multiforme (GBM). The patient presented with symptoms of headache and loss of balance and recurrence on magnetic resonance imaging (MRI). To evaluate the fibroblast activation protein inhibitor (FAPi) expression in the recurrent lesion, an exploratory [68 Ga]Ga-DOTA.SA.FAPi PET/CT scan was performed. The imaging results revealed FAPi expression in the lesion located in the right temporo-parietal region. Based on the findings of FAPi expression, the patient underwent [177Lu]Lu-DOTAGA.Glu.(FAPi)2 treatment. After completing two cycles of [177Lu]Lu-DOTAGA.Glu.(FAPi)2 therapy, a follow-up [68 Ga]Ga-DOTA.SA.FAPi PET/CT scan was conducted. The post-treatment imaging showed a significant reduction in FAPi uptake and regression in the size of the lesion, as well as a decrease in perilesional edema, as observed on the MRI. Furthermore, the patient experienced an improvement in symptoms and performance status. These results suggest that [68 Ga]Ga-DOTA.SA.FAPi monomer imaging and [177Lu]Lu-DOTAGA.Glu.(FAPi)2 dimer therapeutics hold promise for patients with recurrent GBM when other standard-line therapeutic options have been exhausted. This case highlights the potential of using FAPi-based theranostics in the management of recurrent GBM, providing a potential avenue for personalized treatment in patients who have limited treatment options available.