Clinical Trials in Brain Tumor Surgery

Numerical simulation of neural excitation during brain tumor ablation by microsecond pulses

Replacing monopolar pulse with bipolar pulses of the same energized time can minimize unnecessary neurological side effects during irreversible electroporation (IRE). An improved neural excitation model that considers dynamic conductivity and thermal effects during brain tumor IRE ablation was proposed for the first time in this study. Nerve fiber excitation during IRE ablation by applying a monopolar pulse (100 μs) and a burst of bipolar pulses (energized time of 100 μs with both the sub-pulse length and interphase delay of 1 μs) was investigated. Our results suggest that both thermal effects and dynamic conductivity change the onset time of action potential (AP), and dynamic conductivity also changes the hyperpolarization amplitude. Considering both thermal effects and dynamic conductivity, the hyperpolarization amplitude in nerve fibers located 2 cm from the tumor center was reduced by approximately 23.8 mV and the onset time of AP was delayed by approximately 17.5 μs when a 500 V monopolar pulse was applied. Moreover, bipolar pulses decreased the excitable volume of brain tissue by approximately 68.8 % compared to monopolar pulse. Finally, bipolar pulses cause local excitation with lesser damage to surrounding healthy tissue in complete tumor ablation, demonstrating the potential benefits of bipolar pulses in brain tissue ablation.

MicroRNA-219 loaded chitosan nanoparticles for treatment of glioblastoma

Recent evidence has implicated microRNA-219 (miR-219) in regulation of gene contributed in glioblastoma (GBM) pathogenesis. This study aimed to prepare miR-219 in chitosan (CS) nanoparticles (NPs), characterize and investigate their efficacy on human GBM cell line (U87 MG). NPs were prepared using ionic gelation method. The influence of process parameters on physicochemical characteristics of NPs was investigated. Apoptotic effect of miR-219 was examined on U87 MG cells. Formulated NPs showed particle size of 109 ± 2.18 nm, with poly dispersity index equal to 0.2 ± 0.05, and zeta potential of +20.5 ± 0.7 mV. Entrapment efficiency of miR-219 in loaded NP has reached 95%. The in vitro release study demonstrated sustained release pattern of miR-219 from CS-NPs. Gel retardation assay has confirmed the integrity of miR-219 after production process. The fabricated NPs reduced the survival of U87 MG cells to 78% after 24 h of post-transfection, and into 67.5% after 48 h. However, fibroblasts were not affected by the NPs, revealing their specificity for GBM cells. Given the tumour suppressing function of miR-219, and advantage of CS-NPs for gene delivery to the central nervous system, the presented NPs have a great potential for treatment of GBM.

Electroporation-Based Therapy for Brain Tumors: A Review

Electroporation-based therapy (EBT), as a high-voltage-pulse technology has been prevalent with favorable clinical outcomes in the treatment of various solid tumors. This review paper aims to promote the clinical translation of EBT for brain tumors. First, we briefly introduced the mechanism of pore formation in a cell membrane activated by external electric fields using a single cell model. Then, we summarized and discussed the current in vitro and in vivo preclinical studies, in terms of (1) the safety and effectiveness of EBT for brain tumors in animal models, and (2) the blood-brain barrier (BBB) disruption induced by EBT. Two therapeutic effects could be achieved in EBT for brain tumors simultaneously, i.e., the tumor ablation induced by irreversible electroporation (IRE) and transient BBB disruption induced by reversible electroporation (RE). The BBB disruption could potentially improve the uptake of antitumor drugs thereby enhancing brain tumor treatment. The challenges that hinder the application of EBT in the treatment of human brain tumors are discussed in the review paper as well.

High Precision Imaging of Microscopic Spread of Glioblastoma with a Targeted Ultrasensitive SERRS Molecular Imaging Probe

The dismal prognosis of patients with malignant brain tumors such as glioblastoma multiforme (GBM) is attributed mostly to their diffuse growth pattern and early microscopic tumor spread to distant regions of the brain. Because the microscopic tumor foci cannot be visualized with current imaging modalities, it remains impossible to direct treatments optimally. Here we explored the ability of integrin-targeted surface-enhanced resonance Raman spectroscopy (SERRS) nanoparticles to depict the true tumor extent in a GBM mouse model that closely mimics the pathology in humans. The recently developed SERRS-nanoparticles have a sensitivity of detection in the femtomolar range. An RGD-peptide-conjugated version for integrin-targeting (RGD-SERRS) was compared directly to its non-targeted RAD-SERRS control in the same mice via Raman multiplexing. Pre-blocking with RGD peptide before injection of RGD-SERRS nanoparticles was used to verify the specificity of integrin-targeting. In contrast to the current belief that the enhanced permeability and retention (EPR) effect results in a baseline uptake of nanoparticles regardless of their surface chemistry, integrin-targeting was shown to be highly specific, with markedly lower accumulation after pre-blocking. While the non-targeted SERRS particles enabled delineation of the main tumor, the RGD-SERRS nanoparticles afforded a major improvement in visualization of the true extent and the diffuse margins of the main tumor. This included the detection of unexpected tumor areas distant to the main tumor, tracks of migrating cells of 2-3 cells in diameter, and even isolated distant tumor cell clusters of less than 5 cells. This Raman spectroscopy-based nanoparticle-imaging technology holds promise to allow high precision visualization of the true extent of malignant brain tumors.

Guiding brain tumor resection using surface-enhanced Raman scattering nanoparticles and a hand-held Raman scanner

The current difficulty in visualizing the true extent of malignant brain tumors during surgical resection represents one of the major reasons for the poor prognosis of brain tumor patients. Here, we evaluated the ability of a hand-held Raman scanner, guided by surface-enhanced Raman scattering (SERS) nanoparticles, to identify the microscopic tumor extent in a genetically engineered RCAS/tv-a glioblastoma mouse model. In a simulated intraoperative scenario, we tested both a static Raman imaging device and a mobile, hand-held Raman scanner. We show that SERS image-guided resection is more accurate than resection using white light visualization alone. Both methods complemented each other, and correlation with histology showed that SERS nanoparticles accurately outlined the extent of the tumors. Importantly, the hand-held Raman probe not only allowed near real-time scanning, but also detected additional microscopic foci of cancer in the resection bed that were not seen on static SERS images and would otherwise have been missed. This technology has a strong potential for clinical translation because it uses inert gold-silica SERS nanoparticles and a hand-held Raman scanner that can guide brain tumor resection in the operating room.

Clinical trials in neurosurgical oncology

Brain tumors such as diffuse infiltrating gliomas continue to represent a major clinical challenge. Overall survival for patients diagnosed with glioblastoma, the most common primary brain tumor, remains less than 2 years despite intensive multimodal therapy with surgery, radiation, and chemotherapy. However, advances have been made in standard therapies and novel treatments that are showing great potential. These advances reflect careful study performed in the context of clinical trials. Neurosurgeons have played and will continue to play key parts in these studies. In this manuscript, we review clinical trials in neuro-oncology from a neurosurgical point of view and discuss potential roles for neurosurgeons in advancing glioma therapy in the future.

Glioblastoma multiforme: State of the art and future therapeutics

BACKGROUND

Glioblastoma multiforme (GBM) is the most common and lethal primary malignancy of the central nervous system (CNS). Despite the proven benefit of surgical resection and aggressive treatment with chemo- and radiotherapy, the prognosis remains very poor. Recent advances of our understanding of the biology and pathophysiology of GBM have allowed the development of a wide array of novel therapeutic approaches, which have been developed. These novel approaches include molecularly targeted therapies, immunotherapies, and gene therapy.

METHODS

We offer a brief review of the current standard of care, and a survey of novel therapeutic approaches for treatment of GBM.

RESULTS

Despite promising results in preclinical trials, many of these therapies have demonstrated limited therapeutic efficacy in human clinical trials. Thus, although survival of patients with GBM continues to slowly improve, treatment of GBM remains extremely challenging.

CONCLUSION

Continued research and development of targeted therapies, based on a detailed understanding of molecular pathogenesis can reasonably be expected to yield improved outcomes for patients with GBM.

Surgical outcomes in recurrent glioma

Object

The object of this study was to assess outcomes after surgery for recurrent intracranial glioma.

Methods

The authors retrospectively reviewed cases involving adult patients with intracranial glioma patients undergoing initial surgery (biopsy or resection) and one or more additional surgeries at their institution.

Results

A total of 323 operations were performed in 131 patients. The median survival was 76 months after first surgery, 36 months after second, 24 months after third, and 26.5 months after 4 or more surgeries. The overall complication rate was 12.8% after first surgery, 27.0% after second (OR 2.52, p = 0.0068), 22.0% after third (OR 1.92, not statistically significant [NS]), and 22.2% after 4 or more (OR 1.95, NS). Neurological complications occurred in 4.8% of patients at first surgery, 12.1% at second (OR 2.7, p = 0.0437), 8.2% at third (OR 1.75, NS), and 11.1% at 4 or more surgeries (OR 2.4583, NS). Regional complications occurred in 6.2% after first surgery, 9.9% after second surgery (OR 2.30, p = 0.095), 13.7% after third surgery (OR 3.31, p = 0.015), and 22.2% after 4 or more surgeries (OR 5.95, p = 0.056). Systemic complications occurred in 3.2% after first surgery, in 7.3% after second surgery (OR 2.3, p = 0.NS), in 4.1% after third surgery (OR 1.3, NS), and 0% after 4 or more surgeries. Reduction in Karnofsky Performance Status score occurred in 0% after first surgery, 8.1% after second surgery (OR 3.13, p = 0.0018), 10.2% after third surgery (OR 5.52, p < 0.0001), and 11.1% after 4 or more surgeries (OR 1.037, NS).

Conclusions

Postoperative survival is relatively prolonged but complication risk increases in patients with glioma who undergo multiple cranial surgeries. The largest increase in neurological risk occurs between the first and second surgery. In contrast, regional complication risk increases consistently with each surgery. The risk of systemic complications is not significantly altered with increasing surgeries. However, these complications only result in a modestly increased risk of functional decline after 2 or more surgeries. These findings may help counsel patients considering multiple glioma surgeries.

Combination therapy of surgical tumor resection with implantation of a hydrogel containing camptothecin-loaded poly(lactic-co-glycolic acid) microspheres in a C6 rat glioma model

We have developed a drug-loaded poly(lactic-co-glycolic acid) (PLGA) microsphere-containing thermoreversible gelation polymer (TGP) (drug/PLGA/TGP) formulation as a novel device for implantation after surgical glioma resection. TGP is a thermosensitive polymer that is a gel at body temperature and a sol at room temperature. When a drug/PLGA/TGP formulation is injected into a target site, PLGA microspheres in TGP gel localize at the injection site and do not diffuse across the entire brain tissue, and thus, sustained drug release from the PLGA microspheres at the target site is expected. Using in vivo imaging, we confirmed that the implantation of indocyanine green (ICG)/PLGA/TGP formulation exhibited a stronger localization of ICG at the injection site 28 d after injection compared with that of ICG/PLGA formulation. The therapeutic effect (mean survival) was evaluated in a C6 rat glioma model. Surgical tumor resection alone showed almost no effect on survival (controls, 18 d; surgical resection; 18.5 d). Survival was prolonged after the treatment with a camptothecin (CPT; 10 µg)/PLGA/TGP formulation (24 d). The combination treatment of surgical tumor resection and CPT/PLGA/TGP showed almost the same therapeutic effect (24 d) compared with CPT/PLGA/TGP alone, while the combination treatment produced long term survivors (>60 d). Therefore, the CPT/PLGA/TGP formulation can be an effective candidate for localized and sustained long-term glioma therapy.