Resolution of radiation necrosis with bevacizumab following radiation therapy for primary CNS lymphoma

Intra-arterial Bevacizumab in Adult Patients With Steroid-Refractory Cerebral Radiation Necrosis: An Observational Study of Clinical Indications and Outcomes

Background Cerebral radiation necrosis (RN) is a chronic inflammatory process that may develop following radiotherapy for a primary or metastatic brain tumor or arteriovenous malformation (AVM). A single infusion dose of intra-arterial (IA) bevacizumab (BV) is a viable option. The aim of this study was to assess the safety and efficacy of IA BV infusion in patients with steroid-refractory cerebral RN.  Materials and methods A total of 33 patients with imaging-confirmed brain RN underwent at least one IA BV infusion over a 9-year duration. BV was administered as a single 2.5 mg/kg (n=24) or 5.0 mg/kg (n=9) infusion dose.  Results Diagnoses included brain metastasis (17 (51.5%)), AVM (10 (30.3%)), and primary brain tumors (six (18%)). All patients experienced either complete relief or significant symptom improvement after the IA IV infusion. The initial brain MRIs performed following the IA BV infusion revealed a decreased size of the RN in all patients. Two patients had minimal side effects. Of the 16 (48.5%) patients who experienced an RN recurrence, 10 underwent a repeat IA BV infusion. The mean duration between the first IA BV infusion and last follow-up was 23.2 months (range: 0.1-85.2 months). Age (p = 0.00587), tumor pathology (p = 0.03509), and BV dosage (p = 0.02420) were significant predictors of RN recurrence. Conclusions IA infusion of BV was well-tolerated by all patients, with substantial clinical and radiological improvement. Further research is needed to explore additional factors that may impact the effectiveness of BV treatment in RN patients.

A Synthetic Steroid 5α-Androst-3β, 5, 6β-triol Alleviates Radiation-Induced Brain Injury in Mice via Inhibiting GBP5/NF-κB/NLRP3 Signal Axis

Radiotherapy for head and neck tumors can lead to a severe complication known as radiation-induced brain injury (RIBI). However, the underlying mechanism of RIBI development remains unclear, and limited prevention and treatment options are available. Neuroactive steroids have shown potential in treating neurological disorders. 5α-Androst-3β, 5, 6β-triol (TRIOL), a synthetic neuroprotective steroid, holds promise as a treatment candidate for RIBI patients. However, the neuroprotective effects and underlying mechanism of TRIOL on RIBI treatment are yet to be elucidated. In the present study, our findings demonstrate TRIOL's potential as a neuroprotective agent against RIBI. In gamma knife irradiation mouse model, TRIOL treatment significantly reduced brain necrosis volume, microglial activation, and neuronal loss. RNA-sequencing, immunofluorescence, real-time quantitative polymerase chain reaction, siRNA transfection, and western blotting techniques revealed that TRIOL effectively decreased microglial activation, proinflammatory cytokine release, neuron loss, and guanylate-binding protein 5 (GBP5) expression, along with its downstream signaling pathways NF-κB and NLRP3 activation in vitro. In summary, TRIOL effectively alleviate RIBI by inhibiting the GBP5/NF-κB/NLRP3 signal axis, reducing microglia activation and pro-inflammation cytokines release, rescuing neuron loss. This study highlights the potential of TRIOL as a novel and promising therapy drug for RIBI treatment.

Inhibiting astrocyte connexin-43 hemichannels blocks radiation-induced vesicular VEGF-A release and blood-brain barrier dysfunction

Therapeutic brain irradiation with ionizing radiation exerts multiple side effects including barrier leakage that disturbs glial-neuronal functioning and may affect cognition. Astrocytes contribute to barrier leakage by endfeet release of various vasoactive substances acting on capillary endothelial cells forming the barrier. Here, we investigated X-ray effects on astrocytic vesicular transport in mice and determined whether interfering with astrocyte connexins affects radiation-induced barrier leakage. We found that astrocytic VEGF-A-loaded VAMP3 vesicles drastically reorganize starting from 6 h post-irradiation and move in a calcium- and Cx43-dependent manner towards endfeet where VEGF-A is released, provoking barrier leakage. Vesicular transport activation, VEGF-A release and leakage 24 h post-irradiation were all potently inhibited by astrocytic Cx43 KO, Cx43S255/262/279/282A (MK4) mutant mice and TATGap19 inhibition of Cx43 hemichannel opening. Astrocyte VEGF release is a major player in complications of brain irradiation, which can be mitigated by anti-VEGF treatments. Targeting Cx43 hemichannels allows to prevent astrocyte VEGF release at an early stage after brain irradiation.

Refractory seizures secondary to radiation-induced focal cortical dysplasia/neuronal gigantism: illustrative case

BACKGROUND

Focal cortical dysplasia is a structural cause of drug-resistant epilepsy commonly identified in childhood. In rare cases, radiation-induced injury has led to radiation-induced cortical dysplasia, also known as "focal neuronal gigantism."

OBSERVATIONS

The authors present a 53-year-old woman with recurrent status epilepticus events after she had radiation therapy and surgery for a left frontal meningioma several years prior. Imaging revealed findings consistent with radiation necrosis and possible recurrence. The patient's status epilepticus events required escalating therapies to manage. Scalp electroencephalography indicated that the seizure's origin was in the left hemisphere. A craniotomy was performed to remove the left frontal lesion, and histopathology was consistent with radiation-induced focal cortical dysplasia/neuronal gigantism. The patient's seizures ceased following the surgery, and she remains on maintenance antiseizure medications.

LESSONS

Radiation-induced focal cortical dysplasia/neuronal gigantism is an incredibly rare complication of therapy. However, it warrants consideration in the context of radiation necrosis and intractable epilepsy.

Mitigating Radiotoxicity in the Central Nervous System: Role of Proton Therapy

OPINION STATEMENT

Central nervous system (CNS) radiotoxicity remains a challenge in neuro-oncology. Dose distribution advantages of protons over photons have prompted increased use of brain-directed proton therapy. While well-recognized among pediatric populations, the benefit of proton therapy among adults with CNS malignancies remains controversial. We herein discuss the role of protons in mitigating late CNS radiotoxicities in adult patients. Despite limited clinical trials, evidence suggests toxicity profile advantages of protons over conventional radiotherapy, including retention of neurocognitive function and brain volume. Modelling studies predict superior dose conformality of protons versus state-of-the-art photon techniques reduces late radiogenic vasculopathies, endocrinopathies, and malignancies. Conversely, potentially higher brain tissue necrosis rates following proton therapy highlight a need to resolve uncertainties surrounding the impact of variable biological effectiveness of protons on dose distribution. Clinical trials comparing best photon and particle-based therapy are underway to establish whether protons substantially improve long-term treatment-related outcomes in adults with CNS malignancies.

Novel Mechanisms and Future Opportunities for the Management of Radiation Necrosis in Patients Treated for Brain Metastases in the Era of Immunotherapy

Radiation necrosis, also known as treatment-induced necrosis, has emerged as an important adverse effect following stereotactic radiotherapy (SRS) for brain metastases. The improved survival of patients with brain metastases and increased use of combined systemic therapy and SRS have contributed to a growing incidence of necrosis. The cyclic GMP-AMP (cGAMP) synthase (cGAS) and stimulator of interferon genes (STING) pathway (cGAS-STING) represents a key biological mechanism linking radiation-induced DNA damage to pro-inflammatory effects and innate immunity. By recognizing cytosolic double-stranded DNA, cGAS induces a signaling cascade that results in the upregulation of type 1 interferons and dendritic cell activation. This pathway could play a key role in the pathogenesis of necrosis and provides attractive targets for therapeutic development. Immunotherapy and other novel systemic agents may potentiate activation of cGAS-STING signaling following radiotherapy and increase necrosis risk. Advancements in dosimetric strategies, novel imaging modalities, artificial intelligence, and circulating biomarkers could improve the management of necrosis. This review provides new insights into the pathophysiology of necrosis and synthesizes our current understanding regarding the diagnosis, risk factors, and management options of necrosis while highlighting novel avenues for discovery.