CCR2 and CCR5 co-inhibition modulates immunosuppressive myeloid milieu in glioma and synergizes with anti-PD-1 therapy

Immunotherapy has revolutionized the treatment of cancers. Reinvigorating lymphocytes with checkpoint blockade has become a cornerstone of immunotherapy for multiple tumor types, but the treatment of glioblastoma has not yet shown clinical efficacy. A major hurdle to treat GBM with checkpoint blockade is the high degree of myeloid-mediated immunosuppression in brain tumors that limits CD8 T-cell activity. A potential strategy to improve anti-tumor efficacy against glioma is to use myeloid-modulating agents to target immunosuppressive cells, such as myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment. We found that the co-inhibition of the chemokine receptors CCR2 and CCR5 in murine model of glioma improves the survival and synergizes robustly with anti-PD-1 therapy. Moreover, the treatment specifically reduced the infiltration of monocytic-MDSCs (M-MDSCs) into brain tumors and increased lymphocyte abundance and cytokine secretion by tumor-infiltrating CD8 T cells. The depletion of T-cell subsets and myeloid cells abrogated the effects of CCR2 and CCR5 blockade, indicating that while broad depletion of myeloid cells does not improve survival, specific reduction in the infiltration of immunosuppressive myeloid cells, such as M-MDSCs, can boost the anti-tumor immune response of lymphocytes. Our study highlights the potential of CCR2/CCR5 co-inhibition in reducing myeloid-mediated immunosuppression in GBM patients.

The Hospital Frailty Risk Score Independently Predicts Postoperative Outcomes in Glioblastoma Patients

OBJECTIVE

The Hospital Frailty Risk Score (HFRS) is a tool for quantifying patient frailty using International Classification of Diseases, Tenth Revision codes. This study aimed to determine the utility of the HFRS in predicting surgical outcomes after resection of glioblastoma (GBM) and compare its prognostic ability with other validated indices such as American Society of Anesthesiologists score and Charlson Comorbidity Index.

METHODS

A retrospective analysis was conducted using a GBM patient database (2017-2019) at a single institution. HFRS was calculated using International Classification of Diseases, Tenth Revision codes. Bivariate logistic regression was used to model prognostic ability of each frailty index, and model discrimination was assessed using area under the receiver operating characteristic curve. Multivariate linear and logistic regression models were used to assess for significant associations between HFRS and continuous and binary postoperative outcomes, respectively.

RESULTS

The study included 263 patients with GBM. The HFRS had a significantly greater area under the receiver operating characteristic curve compared with American Society of Anesthesiologists score (P = 0.016) and Charlson Comorbidity Index (P = 0.037) for predicting 30-day readmission. On multivariate analysis, the HFRS was significantly and independently associated with hospital length of stay (P = 0.0038), nonroutine discharge (P = 0.018), and 30-day readmission (P = 0.0051).

CONCLUSIONS

The HFRS has utility in predicting postoperative outcomes for patients with GBM and more effectively predicts 30-day readmission than other frailty indices. The HFRS may be used as a tool for optimizing clinical decision making to reduce adverse postoperative outcomes in patients with GBM.

Soluble PD-L1 reprograms blood monocytes to prevent cerebral edema and facilitate recovery after ischemic stroke

Acute cerebral ischemia triggers a profound inflammatory response. While macrophages polarized to an M2-like phenotype clear debris and facilitate tissue repair, aberrant or prolonged macrophage activation is counterproductive to recovery. The inhibitory immune checkpoint Programmed Cell Death Protein 1 (PD-1) is upregulated on macrophage precursors (monocytes) in the blood after acute cerebrovascular injury. To investigate the therapeutic potential of PD-1 activation, we immunophenotyped circulating monocytes from patients and found that PD-1 expression was upregulated in the acute period after stroke. Murine studies using a temporary middle cerebral artery (MCA) occlusion (MCAO) model showed that intraperitoneal administration of soluble Programmed Death Ligand-1 (sPD-L1) significantly decreased brain edema and improved overall survival. Mice receiving sPD-L1 also had higher performance scores short-term, and more closely resembled sham animals on assessments of long-term functional recovery. These clinical and radiographic benefits were abrogated in global and myeloid-specific PD-1 knockout animals, confirming PD-1+ monocytes as the therapeutic target of sPD-L1. Single-cell RNA sequencing revealed that treatment skewed monocyte maturation to a non-classical Ly6Clo, CD43hi, PD-L1+ phenotype. These data support peripheral activation of PD-1 on inflammatory monocytes as a therapeutic strategy to treat neuroinflammation after acute ischemic stroke.

GPR68-ATF4 signaling is a novel prosurvival pathway in glioblastoma activated by acidic extracellular microenvironment

BACKGROUND

Glioblastoma multiforme (GBM) stands as a formidable challenge in oncology because of its aggressive nature and severely limited treatment options. Despite decades of research, the survival rates for GBM remain effectively stagnant. A defining hallmark of GBM is a highly acidic tumor microenvironment, which is thought to activate pro-tumorigenic pathways. This acidification is the result of altered tumor metabolism favoring aerobic glycolysis, a phenomenon known as the Warburg effect. Low extracellular pH confers radioresistant tumors to glial cells. Notably GPR68, an acid sensing GPCR, is upregulated in radioresistant GBM. Usage of Lorazepam, which has off target agonism of GPR68, is linked to worse clinical outcomes for a variety of cancers. However, the role of tumor microenvironment acidification in GPR68 activation has not been assessed in cancer. Here we interrogate the role of GPR68 specifically in GBM cells using a novel highly specific small molecule inhibitor of GPR68 named Ogremorphin (OGM) to induce the iron mediated cell death pathway: ferroptosis.

METHOD

OGM was identified in a non-biased zebrafish embryonic development screen and validated with Morpholino and CRISPR based approaches. Next, A GPI-anchored pH reporter, pHluorin2, was stably expressed in U87 glioblastoma cells to probe extracellular acidification. Cell survival assays, via nuclei counting and cell titer glo, were used to demonstrate sensitivity to GPR68 inhibition in twelve immortalized and PDX GBM lines. To determine GPR68 inhibition's mechanism of cell death we use DAVID pathway analysis of RNAseq. Our major indication, ferroptosis, was then confirmed by western blotting and qRT-PCR of reporter genes including TFRC. This finding was further validated by transmission electron microscopy and liperfluo staining to assess lipid peroxidation. Lastly, we use siRNA and CRISPRi to demonstrate the critical role of ATF4 suppression via GPR68 for GBM survival.

RESULTS

We used a pHLourin2 probe to demonstrate how glioblastoma cells acidify their microenvironment to activate the commonly over expressed acid sensing GPCR, GPR68. Using our small molecule inhibitor OGM and genetic means, we show that blocking GPR68 signaling results in robust cell death in all thirteen glioblastoma cell lines tested, irrespective of genetic and phenotypic heterogeneity, or resistance to the mainstay GBM chemotherapeutic temozolomide. We use U87 and U138 glioblastoma cell lines to show how selective induction of ferroptosis occurs in an ATF4-dependent manner. Importantly, OGM was not-acutely toxic to zebrafish and its inhibitory effects were found to spare non-malignant neural cells.

CONCLUSION

These results indicate GPR68 emerges as a critical sensor for an autocrine pro-tumorigenic signaling cascade triggered by extracellular acidification in glioblastoma cells. In this context, GPR68 suppresses ATF4, inhibition of GPR68 increases expression of ATF4 which leads to ferroptotic cell death. These findings provide a promising therapeutic approach to selectively induce ferroptosis in glioblastoma cells while sparing healthy neural tissue.

An asynchronous web-based intervention for neurosurgery residents to improve education on cost-effective care

OBJECTIVE

To gauge resident knowledge in the socioeconomic aspects of neurosurgery and assess the efficacy of an asynchronous, longitudinal, web-based, socioeconomics educational program tailored for neurosurgery residents.

METHODS

Trainees completed a 20-question pre- and post-intervention knowledge examination including four educational categories: billing/coding, procedure-specific concepts, material costs, and operating room protocols. Structured data from 12 index cranial neurosurgical operations were organized into 5 online, case-based modules sent to residents within a single training program via weekly e-mail. Content from each educational category was integrated into the weekly modules for resident review.

RESULTS

Twenty-seven neurosurgical residents completed the survey. Overall, there was no statistically significant difference between pre- vs post-intervention resident knowledge of billing/coding (79.2 % vs 88.2 %, p = 0.33), procedure-specific concepts (34.3 % vs 39.2 %, p = 0.11), material costs (31.7 % vs 21.6 %, p = 0.75), or operating room protocols (51.7 % vs 35.3 %, p = 0.61). However, respondents' accuracy increased significantly by 40.8 % on questions containing content presented more than 3 times during the 5-week study period, compared to an increased accuracy of only 2.2 % on questions containing content presented less often during the same time period (p = 0.05).

CONCLUSIONS

Baseline resident knowledge in socioeconomic aspects of neurosurgery is relatively lacking outside of billing/coding. Our socioeconomic educational intervention demonstrates some promise in improving socioeconomic knowledge among neurosurgery trainees, particularly when content is presented frequently. This decentralized, web-based approach to resident education may serve as a future model for self-driven learning initiatives among neurosurgical residents with minimal disruption to existing workflows.

Management and Molecular Characterization of Intraventricular Glioblastoma: A Single-Institution Case Series

While the central nervous system (CNS) tumor classification has increasingly incorporated molecular parameters, there is a paucity of literature reporting molecular alterations found in intraventricular glioblastoma (IVGBM), which are rare. We present a case series of nine IVGBMs, including molecular alterations found in standardized next-generation sequencing (NGS). We queried the clinical charts, operative notes, pathology reports, and radiographic images of nine patients with histologically confirmed IVGBM treated at our institution (1995-2021). Routine NGS was performed on resected tumor tissue of two patients. In this retrospective case series of nine patients (22% female, median (range) age: 64.3 (36-85) years), the most common tumor locations were the atrium of the right lateral ventricle (33%) and the septum pellucidum (33%). Five patients had preoperative hydrocephalus, which was managed with intraoperative external ventricular drains in three patients and ventriculoperitoneal shunts in one patient. Hydrocephalus was managed with subtotal resection of a fourth ventricular IVGBM in one patient. The most common surgical approach was transcortical intraventricular (56%). Gross total resection was achieved in two patients, subtotal resection was achieved in six patients, and one patient received a biopsy only. Immunohistochemistry for IDH1 R132H mutant protein was performed in four cases and was negative in all four. Genetic alterations common in glioblastoma, IDH-wildtype, were seen in two cases with available NGS data, including EGFR gene amplification, TERT promoter mutation, PTEN mutation, trisomy of chromosome 7, and monosomy of chromosome 10. Following surgical resection, four patients received adjuvant chemoradiation. Median survival among our cohort was 4.7 months (IQR: 0.9-5.8 months). Management of IVGBM is particularly challenging due to their anatomical location, presentation with obstructive hydrocephalus, and fast growth, necessitating prompt intervention. Additional studies are needed to better understand the genetic landscape of IVGBM compared to parenchymal glioblastoma and may further elucidate the unique pathophysiology of these rare tumors.

The mFI-5 and postoperative outcomes in brain tumor patients: A Bayesian approach to quantifying uncertainty

OBJECTIVE

Prior research has not investigated the uncertainty in the relationship between patient frailty and postoperative outcomes after brain tumor surgery. The present study used Bayesian methods to quantify the statistical uncertainty between the 5-factor modified frailty index (mFI-5) and postoperative outcomes in patients undergoing brain tumor resection.

METHODS

The present study utilized retrospective data collected from patients undergoing brain tumor resection over a two-year period (2017-2019). Posterior probability distributions were used to estimate means of model parameters that are most likely given the priors and the data. Additionally, 95% credible intervals (95% CrI) were constructed for each parameter estimate.

RESULTS

Our patient cohort included 2,519 patients with a mean age of 55.27 years. Our multivariate analysis demonstrated that each point increase in mFI-5 score was associated with an 18.76% (95% CrI=[14.35%-23.36%]) increase in hospital LOS and a 9.37% (CrI=[6.82%-12.07%]) increase in hospital charges. We also noted an association between increasing mFI-5 score and greater odds of experiencing a postoperative complication (OR=1.58, CrI=[1.34-1.87]) and experiencing nonroutine discharge (OR=1.54, CrI=[1.34-1.80]). However, there was no meaningful statistical association between mFI-5 score and 90-day hospital readmission (OR=1.16, CrI=[0.98-1.36]) or between mFI-5 score and 90-day mortality (OR=1.12, CrI=[0.83-1.50]).

CONCLUSION

While mFI-5 scores may be able to effectively predict short term outcomes such as LOS, our results demonstrate no meaningful association between mFI-5 scores and 90-day readmission or 90-day mortality. Our study highlights the need for rigorously quantifying statistical uncertainty in order to safely risk-stratify neurosurgical patients.

Establishing proof of concept for sonolucent cranioplasty and point of care ultrasound imaging after posterior fossa decompression for Chiari malformation

BACKGROUND

Evaluation after posterior fossa decompression for Chiari malformation can require repeated imaging, particularly with persistent symptoms. Typically, CT or MRI is used. However, CT carries radiation risk and MRI is costly. Ultrasound is an inexpensive, radiation-free, point-of-care modality that has, thus far, been limited by intact skull and traditional cranioplasty materials. Ultrasound also allows for imaging in different head positions and body postures, which may lend insight into cause for persistent symptoms despite adequate decompression on traditional neutral static CT or MRI. We evaluate safety and feasibility of ultrasound as a post-operative imaging modality in patients reconstructed with sonolucent cranioplasty during posterior fossa decompression for Chiari malformation.

METHODS

Outcomes were analyzed for 26 consecutive patients treated with a Chiari-specific sonolucent cranioplasty. This included infection, need for revision, CSF leak, and pseudomeningocele. Ultrasound was performed point-of-care in the outpatient clinic by the neurosurgery team to assess feasibility.

RESULTS

In eight months mean follow up, there were no surgical site infections or revisions with this novel sonolucent cranioplasty. Posterior fossa anatomy was discernable via transcutaneous ultrasound obtained point-of-care in the clinic setting at follow up visits.

CONCLUSION

We demonstrate proof of concept for ultrasound as a post-operative imaging modality after posterior fossa decompression for Chiari malformation. With further investigation, ultrasound may prove to serve as an alternative to CT and MRI in this patient population, or as an adjunct to provide positional and dynamic information. Use of sonolucent cranioplasty is safe. This technique deserves further study.

Deoxyhypusine hydroxylase: A novel therapeutic target differentially expressed in short-term vs long-term survivors of glioblastoma

Glioblastoma (GB) is the most aggressive neoplasm of the brain. Poor prognosis is mainly attributed to tumor heterogeneity, invasiveness and drug resistance. Only a small fraction of GB patients survives longer than 24 months from the time of diagnosis (ie, long-term survivors [LTS]). In our study, we aimed to identify molecular markers associated with favorable GB prognosis as a basis to develop therapeutic applications to improve patients' outcome. We have recently assembled a proteogenomic dataset of 87 GB clinical samples of varying survival rates. Following RNA-seq and mass spectrometry (MS)-based proteomics analysis, we identified several differentially expressed genes and proteins, including some known cancer-related pathways and some less established that showed higher expression in short-term (<6 months) survivors (STS) compared to LTS. One such target found was deoxyhypusine hydroxylase (DOHH), which is known to be involved in the biosynthesis of hypusine, an unusual amino acid essential for the function of the eukaryotic translation initiation factor 5A (eIF5A), which promotes tumor growth. We consequently validated DOHH overexpression in STS samples by quantitative polymerase chain reaction (qPCR) and immunohistochemistry. We further showed robust inhibition of proliferation, migration and invasion of GB cells following silencing of DOHH with short hairpin RNA (shRNA) or inhibition of its activity with small molecules, ciclopirox and deferiprone. Moreover, DOHH silencing led to significant inhibition of tumor progression and prolonged survival in GB mouse models. Searching for a potential mechanism by which DOHH promotes tumor aggressiveness, we found that it supports the transition of GB cells to a more invasive phenotype via epithelial-mesenchymal transition (EMT)-related pathways.

Self-assembling paclitaxel-mediated stimulation of tumor-associated macrophages for postoperative treatment of glioblastoma

The unique cancer-associated immunosuppression in brain, combined with a paucity of infiltrating T cells, contributes to the low response rate and poor treatment outcomes of T cell-based immunotherapy for patients diagnosed with glioblastoma multiforme (GBM). Here, we report on a self-assembling paclitaxel (PTX) filament (PF) hydrogel that stimulates macrophage-mediated immune response for local treatment of recurrent glioblastoma. Our results suggest that aqueous PF solutions containing aCD47 can be directly deposited into the tumor resection cavity, enabling seamless hydrogel filling of the cavity and long-term release of both therapeutics. The PTX PFs elicit an immune-stimulating tumor microenvironment (TME) and thus sensitizes tumor to the aCD47-mediated blockade of the antiphagocytic "don't eat me" signal, which subsequently promotes tumor cell phagocytosis by macrophages and also triggers an antitumor T cell response. As adjuvant therapy after surgery, this aCD47/PF supramolecular hydrogel effectively suppresses primary brain tumor recurrence and prolongs overall survivals with minimal off-target side effects.

Abstract 443: Therapeutic targeting of GPR68 activated by acidic extracellular microenvironment induces ferroptosis in glioblastoma cells

The Warburg Effect is a common feature of cancer cells characterized by increased glucose uptake and fermentation of glucose to lactate even in the presence of oxygen. While it is commonly accepted that Warburg Effect promotes the growth, survival, proliferation, and long-term maintenance of cancers, its precise function and its downstream mediators remain unclear. A key physiological consequence of the Warburg effect is lactate secretion, which acidifies the tumor milieu, thought to promote oncogenesis and confer tumor resistance to chemotherapy and radiotherapy. Glioblastoma multiforme (GBM) is one of the most aggressive and deadly cancers, characterized by cellular heterogeneity and plasticity, which are thought to drive extreme therapeutic resistance. Despite their heterogeneity, common hallmarks of GBM tumors are high levels of aerobic glycolysis (“Warburg Effect”) and a resultant acidic tumor microenvironment (TME), which promotes tumor progression. In an in vivo zebrafish developmental screen, we identified ogremorphin (OGM), a small molecule inhibitor of GPR68/OGR-1, a G-protein coupled receptor (GPCR) which is activated by extracellular protons. Using ogremorphin and pHluorin2-GPI, a novel sensor of extracellular acidification, we demonstrate that glioblastoma cells acidify their own environment in vitro and activate GPR68, and visualize, for the first time, the establishment of the acidic extracellular microenvironment during the formation of GBM spheroids in vitro. Selective inhibition of GPR68 causes robust cell death in all 12 glioblastoma cell lines tested to date, despite genetic and molecular heterogeneity, without toxicity on healthy cells in whole animals. Mechanistically, GPR68 inhibition activates ferroptosis, a programmed cell death characterized by lipid peroxidation, in an ATF4 (activating transcription factor 4)-dependent manner. Finally, in GBM cells, ogremorphin treatment demonstrates strong synergistic effects with the frontline therapeutics temozolomide and ionizing radiation. Our results indicate that GPR68 activation by extracellular acidification is a key cancer survival pathway downstream of the Warburg Effect, and that GPR68 inhibition, either alone or in combination with temozolomide and radiation therapy, is a promising therapeutic approach to selectively induce ferroptosis in GBM tumors.

Citation Format: Charles H. Williams, Leif R. Neitzel, Jessica Cornell, Samantha Rea, Ian Mills, Maya Silver-Isenstadt, Jovanni D. Ahmad, Henry Brem, Betty Tyler, Eli E. Bar, Charles C. Hong. Therapeutic targeting of GPR68 activated by acidic extracellular microenvironment induces ferroptosis in glioblastoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 443.

First Experience With Postoperative Transcranial Ultrasound Through Sonolucent Burr Hole Covers in Adult Hydrocephalus Patients

BACKGROUND

Managing patients with hydrocephalus and cerebrospinal fluid (CSF) disorders requires repeated head imaging. In adults, it is typically computed tomography (CT) or less commonly magnetic resonance imaging (MRI). However, CT poses cumulative radiation risks and MRI is costly. Ultrasound is a radiation-free, relatively inexpensive, and optionally point-of-care alternative, but is prohibited by very limited windows through an intact skull.

OBJECTIVE

To describe our initial experience with transcutaneous transcranial ultrasound through sonolucent burr hole covers in postoperative hydrocephalus and CSF disorder patients.

METHODS

Using cohort study design, infection and revision rates were compared between patients who underwent sonolucent burr hole cover placement during new ventriculoperitoneal shunt placement and endoscopic third ventriculostomy over the 1-year study time period and controls from the period 1 year before. Postoperatively, trans-burr hole ultrasound was performed in the clinic, at bedside inpatient, and in the radiology suite to assess ventricular anatomy.

RESULTS

Thirty-seven patients with sonolucent burr hole cover were compared with 57 historical control patients. There was no statistically significant difference in infection rates between the sonolucent burr hole cover group (1/37, 2.7%) and the control group (0/57, P = .394). Revision rates were 13.5% vs 15.8% (P = 1.000), but no revisions were related to the burr hole or cranial hardware.

CONCLUSION

Trans-burr hole ultrasound is feasible for gross evaluation of ventricular caliber postoperatively in patients with sonolucent burr hole covers. There was no increase in infection rate or revision rate. This imaging technique may serve as an alternative to CT and MRI in the management of select patients with hydrocephalus and CSF disorders.

Patient Safety Indicator 04 Does Not Consistently Identify Failure to Rescue in the Neurosurgical Population

BACKGROUND

Improving neurosurgical quality metrics necessitates the analysis of patient safety indicator (PSI) 04, a measure of failure to rescue (FTR).

OBJECTIVE

To demonstrate that PSI 04 is not an appropriate measure for capturing FTR within neurosurgery.

METHODS

We conducted a single-center retrospective cohort study. Patients from January 1, 2017 to June 1, 2021, who sustained a PSI 04-attributed complication (pneumonia, deep vein thrombosis/pulmonary embolism, sepsis, shock/cardiac arrest, or gastrointestinal hemorrhage/acute ulcer), underwent a neurosurgical procedure, had inpatient mortality, and were identified using patient safety indicator 04 (PSI 04) tracking algorithm. The primary outcome was whether the attributed PSI 04 designation was the primary driver of mortality.

RESULTS

We identified 67 patients who met the PSI 04 criteria (median age, 61 years; female sex, 43.4%). Nearly 20% of patients met the PSI complication criteria before admission. Patients who underwent emergent bedside procedures were more likely to present with a poor Glasgow Coma Scale ( P = .016), more likely to be intubated before admission ( P = .016), and less likely to have mortality due to a PSI 04-related complication ( P = .002). PSI 04-related complications were identified as the cause of death in only 43.2% of cases. Procedures occurring in the interventional radiology suite (odds ratio, 23.2; 95% CI, 3.5-229.3; P = .003) or the operating room (odds ratio, 6.2; 95% CI, 1.25-39.5; P = .03) were more likely to have mortality because of a PSI 04-related complication compared with bedside procedures.

CONCLUSION

In total, 65.7% of patients were inappropriately flagged as meeting PSI 04 criteria. PSI 04 currently identifies patients with complications unrelated to operating room procedures. Improvement in patient safety within neurosurgery necessitates the development of a subspecialty specific measure to capture FTR.

Recruitment of women in neurosurgery: a 7-year quantitative analysis

OBJECTIVE

The authors aimed to characterize which US medical schools have the most female neurosurgery residents and to identify potential associations between medical school characteristics and successful recruitment of women pursuing a neurosurgery career.

METHODS

The authors evaluated a total of 1572 residents in US neurosurgery programs accredited by the Accreditation Council for Graduate Medical Education as of February 2021, representing match cohorts from 2014 to 2020. The authors extracted US medical school characteristics and ranked schools based on the percentages of women graduates entering neurosurgery. They additionally studied yearly trends of the percentage of women constituting incoming neurosurgery resident cohorts as well as associations between female recruitment percentage and medical school characteristics using univariable and stepwise multivariable linear regression (including significant univariable factors).

RESULTS

The cohort consisted of 1255 male and 317 (20%) female residents. Yearly trends indicated a significant drop in incoming female residents in 2016, followed by significant increases in 2017 and 2019. On multivariable analysis, the following factors were associated with a higher average percentage of female graduates entering neurosurgery: total affiliated neurosurgery clinical faculty (β = 0.006, 95% CI 0.001-0.011, p = 0.01), allopathic versus osteopathic schools (β = 0.231, 95% CI 0.053-0.409, p = 0.01), and top 10 U.S. News & World Report ranking (β = 0.380, 95% CI 0.129-0.589, p < 0.01). When the number of female clinical faculty was added to the model, the variable was not statistically significant. Multivariable bibliometric analyses indicated a higher mean preresidency H-index for men, with an even greater gender difference identified in the 2021 H-index.

CONCLUSIONS

This study characterizes which medical schools are most successful at recruiting female students who constituted the total neurosurgery resident workforce of the 2020-2021 academic year. The overall number of clinical neurosurgery faculty rather than faculty gender was independently associated with female recruitment. Gender differences in research productivity persisted with control for confounders and increased between preresidency and 2021 time points. Such understanding of factors that influence the recruitment of women can help improve female representation in neurosurgery residency training moving forward.

Automatic detection of foreign body objects in neurosurgery using a deep learning approach on intraoperative ultrasound images: From animal models to first in-human testing

Objects accidentally left behind in the brain following neurosurgical procedures may lead to life-threatening health complications and invasive reoperation. One of the most commonly retained surgical items is the cotton ball, which absorbs blood to clear the surgeon’s field of view yet in the process becomes visually indistinguishable from the brain parenchyma. However, using ultrasound imaging, the different acoustic properties of cotton and brain tissue result in two discernible materials. In this study, we created a fully automated foreign body object tracking algorithm that integrates into the clinical workflow to detect and localize retained cotton balls in the brain. This deep learning algorithm uses a custom convolutional neural network and achieves 99% accuracy, sensitivity, and specificity, and surpasses other comparable algorithms. Furthermore, the trained algorithm was implemented into web and smartphone applications with the ability to detect one cotton ball in an uploaded ultrasound image in under half of a second. This study also highlights the first use of a foreign body object detection algorithm using real in-human datasets, showing its ability to prevent accidental foreign body retention in a translational setting.

SURG-40. SINGLE-STAGE RECONSTRUCTION FOLLOWING ONCOLOGIC RESECTION OF BRAIN TUMORS WITH SKULL INVASION

BACKGROUND: Craniectomies requiring skull reconstruction are indicated following oncological resection of masses involving the underlying brain and/or skull. Immediate cranioplasties have previously been performed using suboptimal hand-bending or molding techniques using ‘‘off – the – shelf’’ products. Today with computer – aided design, customized craniofacial implants have become widely available for personalized reconstruction of resected bone and soft tissue. We present the largest series to date of single stage reconstruction using alloplastic biomaterials in consecutive patient series with oversized customized implants.In total, 56 patients underwent resection of skull neoplasms and subsequent cranioplasty reconstruction using customized implants. The most common neoplasms were meningiomas (39%). The most common complications seen among patients were dehiscence – (7%), and extrusion of implant – (3.5%). There was no significant difference in the incidence of postoperative complications between patients who had postoperative chemotherapy/radiotherapy versus those that did not (22.2% versus 13.1%, P 0.39). One-year follow-up revealed acceptable cranial contour and symmetry in all 56 cases.

Predictors of surgical site infection in glioblastoma patients undergoing craniotomy for tumor resection

OBJECTIVE

Surgical site infections (SSIs) burden patients and healthcare systems, often requiring additional intervention. The objective of this study was to identify the relationship between preoperative predictors inclusive of scalp incision type and postoperative SSI following glioblastoma resection.

METHODS

The authors retrospectively reviewed cases of glioblastoma resection performed at their institution from December 2006 to December 2019 and noted preoperative demographic and clinical presentations, excluding patients missing these data. Preoperative nutritional indices were available for a subset of cases. Scalp incisions were categorized as linear/curvilinear, reverse question mark, trapdoor, or frontotemporal. Patients were dichotomized by SSI incidence. Multivariable logistic regression was used to determine predictors of SSI.

RESULTS

A total of 911 cases of glioblastoma resection were identified, 30 (3.3%) of which demonstrated postoperative SSI. There were no significant differences in preoperative malnutrition or number of surgeries between SSI and non-SSI cases. The SSI cases had a significantly lower preoperative Karnofsky Performance Status (KPS) than the non-SSI cases (63.0 vs 75.1, p < 0.0001), were more likely to have prior radiation history (43.3% vs 26.4%, p = 0.042), and were more likely to have received steroids both preoperatively and postoperatively (83.3% vs 54.5%, p = 0.002). Linear/curvilinear incisions were more common in non-SSI than in SSI cases (56.9% vs 30.0%, p = 0.004). Trapdoor scalp incisions were more frequent in SSI than non-SSI cases (43.3% vs 24.2%, p = 0.012). On multivariable analysis, a lower preoperative KPS (OR 1.04, 95% CI 1.02–1.06), a trapdoor scalp incision (OR 3.34, 95% CI 1.37–8.49), and combined preoperative and postoperative steroid administration (OR 3.52, 95% CI 1.41–10.7) were independently associated with an elevated risk of postoperative SSI.

CONCLUSIONS

The study findings indicated that SSI risk following craniotomy for glioblastoma resection may be elevated in patients with a low preoperative KPS, a trapdoor scalp incision during surgery, and steroid treatment both preoperatively and postoperatively. These data may help guide future operative decision-making for these patients.

Predictors and Impact of Postoperative 30-Day Readmission in Glioblastoma

BACKGROUND

Postoperative 30-day readmissions have been shown to negatively affect survival and other important outcomes in patients with glioblastoma (GBM).

OBJECTIVE

To further investigate patient readmission risk factors of primary and recurrent patients with GBM.

METHODS

The authors retrospectively reviewed records of 418 adult patients undergoing 575 craniotomies for histologically confirmed GBM at an academic medical center. Patient demographics, comorbidities, and clinical characteristics were collected and compared by patient readmission status using chi-square and Mann-Whitney U testing. Multivariable logistic regression was performed to identify risk factors that predicted 30-day readmissions.

RESULTS

The cohort included 69 (12%) 30-day readmissions after 575 operations. Readmitted patients experienced significantly lower median overall survival (11.3 vs 16.4 months, P = .014), had a lower mean Karnofsky Performance Scale score (66.9 vs 74.2, P = .005), and had a longer initial length of stay (6.1 vs 5.3 days, P = .007) relative to their nonreadmitted counterparts. Readmitted patients experienced more postoperative deep vein thromboses or pulmonary embolisms (12% vs 4%, P = .006), new motor deficits (29% vs 14%, P = .002), and nonhome discharges (39% vs 22%, P = .005) relative to their nonreadmitted counterparts. Multivariable analysis demonstrated increased odds of 30-day readmission with each 10-point decrease in Karnofsky Performance Scale score (odds ratio [OR] 1.32, P = .002), each single-point increase in 5-factor modified frailty index (OR 1.51, P = .016), and initial presentation with cognitive deficits (OR 2.11, P = .013).

CONCLUSION

Preoperatively available clinical characteristics strongly predicted 30-day readmissions in patients undergoing surgery for GBM. Opportunities may exist to optimize preoperative and postoperative management of at-risk patients with GBM, with downstream improvements in clinical outcomes.

MCP-1/CCR2 axis inhibition sensitizes the brain microenvironment against melanoma brain metastasis progression

Development of resistance to chemo- and immunotherapies often occurs following treatment of melanoma brain metastasis (MBM). The brain microenvironment (BME), particularly astrocytes, cooperate toward MBM progression by upregulating secreted factors, among which we found that monocyte chemoattractant protein-1 (MCP-1) and its receptors, CCR2 and CCR4, were overexpressed in MBM compared with primary lesions. Among other sources of MCP-1 in the brain, we show that melanoma cells altered astrocyte secretome and evoked MCP-1 expression and secretion, which in turn induced CCR2 expression in melanoma cells, enhancing in vitro tumorigenic properties, such as proliferation, migration, and invasion of melanoma cells. In vivo pharmacological blockade of MCP-1 or molecular knockout of CCR2/CCR4 increased the infiltration of cytotoxic CD8⁺ T cells and attenuated the immunosuppressive phenotype of the BME as shown by decreased infiltration of Tregs and tumor-associated macrophages/microglia in several models of intracranially injected MBM. These in vivo strategies led to decreased MBM outgrowth and prolonged the overall survival of the mice. Our findings highlight the therapeutic potential of inhibiting interactions between BME and melanoma cells for the treatment of this disease.

Home Program Matching in Neurosurgical Residency Programs: A 7-Year Study

OBJECTIVE

To determine home program matching percentage (staying in a program affiliated with one's medical school) for each neurosurgical residency program in the United States. Secondarily, to elucidate both program-level and resident characteristics associated with home program matching.

METHODS

Demographic and bibliometric characteristics were collected for 1572 residents in US-based and Accreditation Council for Graduate Medical Education (ACGME)-accredited neurosurgery programs over the 2014 to 2020 match period using publicly available websites. Program characteristics were collected, including number of clinical faculty, top 20 Doximity research ranking, top 10 Doximity reputation ranking, top 10 U.S. News department ranking, affiliation with a U.S. News top 10 medical school, and geographic region. Programs were ranked according to home program matching percentage and associations were statistically evaluated.

RESULTS

The average home program matching percentage per residency was 18.6%. New York Presbyterian/Columbia retained the largest percentage of its own medical students with a home program matching percentage of 57.14%. From the resident frame of reference, only a higher preresidency H-index (3.7 ± 4.0 vs. 3.2 ± 3.7, p=0.033) was significantly associated with home program matching. From a program perspective, program size (standardized β=0.234, p=0.006), Doximity research (standardized β=0.206, p=0.031), Doximity reputation (standardized β=0.196, p=0.040), and U.S. News program rankings (standardized β=0.200, p=0.036) were all significantly associated with home program matching. Overall home program matching percentage remained relatively constant over the 2014-2020 time period.

CONCLUSIONS

The results of this study delineate home program matching patterns on a program-by-program level for U.S. neurosurgical residency programs.

Impact of virtual vs. in-person interviews among neurosurgery residency applicants

BACKGROUND

The interview is considered a key factor in selecting residents in various medical and surgical specialties. However, the reliability of the interview process in selecting neurosurgery training program applicants remains largely under-investigated.

OBJECTIVE

To investigate the reliability of the interview process for neurosurgery residency applicants and to evaluate the impact of virtual interviews on this process.

METHODS

We analyzed the records of neurosurgery residency applicant interviews at our institution between 2016 and 2021. An average of 20 neurosurgery faculty members (clinical and research) interviewed each applicant and graded them 1 (best) to 4 (worst). Intraclass correlation coefficient (ICC) and Levene's test were used to assess the inter-rater and intra-rater reliability, respectively.

RESULTS

214 neurosurgery residency applicants were interviewed at a single institution between 2016 and 2021. The mean applicant rating each year ranged from 1.77 to 1.92. Inter-rater agreement was relatively poor in each year, (ICC < 0.5, P < 0.05). Among 60% of the raters, variability of scores significantly changed from year to year, (p < 0.05). When comparing the scores submitted during the virtual interview process (2021) with the scores submitted in the previous years (2016-2020), 2 interviewers (10%) had less variability using the virtual process.

CONCLUSION

Our analysis found that the current interview process for neurosurgery residency applicants' selection suffers from poor inter- and intra-rater reliability. Virtual interviews may be part of a cost-effective strategy to improve the reliability of the interview process. Further validation is needed, as well as identification of novel strategies to maximize the reliability of the selection process.

Clinical features and surgical outcomes of intracranial and spinal cord subependymomas

OBJECTIVE

Subependymomas are low-grade ependymal tumors whose clinical characteristics, radiographic features, and postsurgical outcomes are incompletely characterized due to their rarity. The authors present an institutional case series and a systematic literature review to achieve a better understanding of subependymomas.

METHODS

Adult patients with histologically confirmed subependymoma or mixed subependymoma-ependymoma surgically treated at a tertiary hospital between 1992 and 2020 were identified. A systematic literature review of the PubMed, Embase, Web of Science, and Google Scholar databases from inception until December 4, 2020, was conducted according to PRISMA guidelines. Data extracted from both groups included demographics, radiographic features, tumor characteristics, management, and follow-up variables.

RESULTS

Forty-eight unique patients with subependymoma were identified by chart review; of these patients, 8 (16.7%) had mixed subependymoma-ependymoma tumors. The median age at diagnosis was 49 years (IQR 19.8 years), and 26 patients (54.2%) were male. Forty-two patients (87.5%) had intracranial subependymomas, and 6 (12.5%) had spinal tumors. The most common presentation was headache (n = 20, 41.7%), although a significant number of tumors were diagnosed incidentally (n = 16, 33.3%). Among the 42 patients with intracranial tumors, 15 (35.7%) had hydrocephalus, and the most common surgical strategy was a suboccipital approach with or without C1 laminectomy (n = 26, 61.9%). Gross-total resection (GTR) was achieved in 33 cases (68.7%), and 2 patients underwent adjuvant radiotherapy. Most patients had no major postsurgical complications (n = 34, 70.8%), and only 1 (2.1%) had recurrence after GTR. Of 2036 reports initially identified in the systematic review, 39 were eligible for inclusion, comprising 477 patients. Of 462 patients for whom tumor location was reported, 406 (87.9%) were intracranial, with the lateral ventricle as the most common location (n = 214, 46.3%). Spinal subependymomas occurred in 53 patients (11.5%), with 3 cases (0.6%) in multiple locations. Similar to the case series at the authors' institution, headache was the most common presenting symptom (n = 231, 54.0%) among the 428 patients whose presentation was reported. Twenty-seven patients (6.3%) were diagnosed incidentally, and 36 cases (8.4%) were found at autopsy. Extent of resection was reported for 350 patients, and GTR was achieved in 250 (71.4%). Fifteen of 337 patients (4.5%) had recurrence or progression.

CONCLUSIONS

The authors' case series and literature review demonstrate that patients with subependymoma are well managed with resection and generally have a favorable prognosis.

Synergy between glutamate modulation and anti-programmed cell death protein 1 immunotherapy for glioblastoma

OBJECTIVE

Immune checkpoint inhibitors such as anti-programmed cell death protein 1 (anti-PD-1) have shown promise for the treatment of cancers such as melanoma, but results for glioblastoma (GBM) have been disappointing thus far. It has been suggested that GBM has multiple mechanisms of immunosuppression, indicating a need for combinatorial treatment strategies. It is well understood that GBM increases glutamate in the tumor microenvironment (TME); however, the significance of this is not well understood. The authors posit that glutamate upregulation in the GBM TME is immunosuppressive. The authors utilized a novel glutamate modulator, BHV-4157, to determine synergy between glutamate modulation and the well-established anti-PD-1 immunotherapy for GBM.

METHODS

C57BL/6J mice were intracranially implanted with luciferase-tagged GL261 glioma cells. Mice were randomly assigned to the control, anti-PD-1, BHV-4157, or combination anti-PD-1 plus BHV-4157 treatment arms, and median overall survival was assessed. In vivo microdialysis was performed at the tumor site with administration of BHV-4157. Intratumoral immune cell populations were characterized with immunofluorescence and flow cytometry.

RESULTS

The BHV-4157 treatment arm demonstrated improved survival compared with the control arm (p < 0.0001). Microdialysis demonstrated that glutamate concentration in TME significantly decreased after BHV-4157 administration. Immunofluorescence and flow cytometry demonstrated increased CD4+ T cells and decreased Foxp3+ T cells in mice that received BHV-4157 treatment. No survival benefit was observed when CD4+ or CD8+ T cells were depleted in mice prior to BHV-4157 administration (p < 0.05).

CONCLUSIONS

In this study, the authors showed synergy between anti-PD-1 immunotherapy and glutamate modulation. The authors provide a possible mechanism for this synergistic benefit by showing that BHV-4157 relies on CD4+ and CD8+ T cells. This study sheds light on the role of excess glutamate in GBM and provides a basis for further exploring combinatorial approaches for the treatment of this disease.

Impact of international research fellows in neurosurgery: results from a single academic center

OBJECTIVE

International research fellows have been historically involved in academic neurosurgery in the United States (US). To date, the contribution of international research fellows has been underreported. Herein, the authors aimed to quantify the academic output of international research fellows in the Department of Neurosurgery at The Johns Hopkins University School of Medicine.

METHODS

Research fellows with Doctor of Medicine (MD), Doctor of Philosophy (PhD), or MD/PhD degrees from a non-US institution who worked in the Hopkins Department of Neurosurgery for at least 6 months over the past decade (2010-2020) were included in this study. Publications produced during fellowship, number of citations, and journal impact factors (IFs) were analyzed using ANOVA. A survey was sent to collect information on personal background, demographics, and academic activities.

RESULTS

Sixty-four international research fellows were included, with 42 (65.6%) having MD degrees, 17 (26.6%) having PhD degrees, and 5 (7.8%) having MD/PhD degrees. During an average 27.9 months of fellowship, 460 publications were produced in 136 unique journals, with 8628 citations and a cumulative journal IF of 1665.73. There was no significant difference in total number of publications, first-author publications, and total citations per person among the different degree holders. Persons holding MD/PhDs had a higher number of citations per publication per person (p = 0.027), whereas those with MDs had higher total IFs per person (p = 0.048). Among the 43 (67.2%) survey responders, 34 (79.1%) had nonimmigrant visas at the start of the fellowship, 16 (37.2%) were self-paid or funded by their country of origin, and 35 (81.4%) had mentored at least one US medical student, nonmedical graduate student, or undergraduate student.

CONCLUSIONS

International research fellows at the authors' institution have contributed significantly to academic neurosurgery. Although they have faced major challenges like maintaining nonimmigrant visas, negotiating cultural/language differences, and managing self-sustainability, their scientific productivity has been substantial. Additionally, the majority of fellows have provided reciprocal mentorship to US students.

Combined Intracranial Acriflavine, Temozolomide and Radiation Extends Survival in a Rat Glioma Model

Glioblastomas have been historically difficult to treat with poor long-term survival. With novel strategies focused on targeting hypoxia-inducible factor (HIF) regulatory pathways, recent evidence has shown that Acriflavine (ACF) can effectively target glioma invasiveness and recurrence. However, local delivery of ACF and its combinatory effects with Temozolomide (TMZ) and radiation therapy (XRT) have not yet been optimized. In this study we test a novel polymeric matrix that can gradually release ACF at the tumor bed site in combination with systemic TMZ and XRT. In vitro cytotoxicity assays of ACF in combination with TMZ and XRT were performed on rodent and human cell lines with CCK-8 and flow cytometry. In vitro drug release was measured and intracranial safety was assessed in tumor-free animals. Finally, efficacy was assessed in an intracranial gliosarcoma model and combination therapy with TMZ and XRT evaluated. Combination therapy of ACF, TMZ, and XRT was able to reduce cell viability and induce apoptosis in glioma cells. In vitro and in vivo release of ACF was measured in benchtop and animal models. Efficacy was established in an in vivo gliosarcoma model in which intracranial ACF (p<0.01) significantly improved median survival and the combination therapy of ACF, TMZ and XRT (p<0.01) significantly improved median survival and led to long-term survival (LTS). We provide evidence that ACF, combined with TMZ and XRT, led to LTS in an intracranial model of rat gliosarcoma. These findings, in combination with the use of a novel polymeric matrix that allows more gradual drug delivery, constitute a first step in the translation of this novel strategy to human use.

Predicting High-Value Care Outcomes After Surgery for Non-Skull Base Meningiomas

OBJECTIVE

A need exists to better understand the prognostic factors that influence high-value care outcomes after meningioma surgery. The goal of the present study was to develop predictive models to determine the patients at risk of experiencing an extended hospital length of stay (LOS), nonroutine discharge disposition, and/or a 90-day hospital readmission after non-skull base meningioma resection.

METHODS

In the present study, we analyzed the data from 396 patients who had undergone surgical resection of non-skull base meningiomas at a single institution between January 1, 2005 and December 31, 2020. The Mann-Whitney U test was used for bivariate analysis of the continuous variables and the Fisher exact test for bivariate analysis of the categorical variables. A multivariate analysis was conducted using logistic regression models.

RESULTS

Most patients had had a falcine or parasagittal meningioma (66.2%), with the remainder having convexity (31.8%) or intraventricular (2.0%) tumors. Nonelective surgery (P < 0.0001) and an increased tumor volume (P = 0.0022) were significantly associated with a LOS >4 days on multivariate analysis. The independent predictors of a nonroutine discharge disposition included male sex (P = 0.0090), nonmarried status (P = 0.024), nonelective surgery (P = 0.0067), tumor location within the parasagittal or intraventricular region (P = 0.0084), and an increased modified frailty index score (P = 0.039). Hospital readmission within 90 days was independently associated with nonprivate insurance (P = 0.010) and nonmarried status (P = 0.0081). Three models predicting for a prolonged LOS, nonroutine discharge disposition, and 90-day readmission were implemented in the form of an open-access, online calculator (available at: https://neurooncsurgery3.shinyapps.io/non_skull_base_meningiomas/).

CONCLUSIONS

After external validation, our open-access, online calculator could be useful for assessing the likelihood of adverse postoperative outcomes for patients undergoing surgery of non-skull base meningioma.

The role of anticoagulation for superior sagittal sinus thrombosis following craniotomy for resection of parasagittal/parafalcine meningiomas

OBJECTIVE

The safety and efficacy of anticoagulation in managing superior sagittal sinus (SSS) thrombosis remains unclear. The present study investigated the relationship between anticoagulation and cerebrovascular complications in parasagittal/parafalcine meningioma patients presenting with post-surgical SSS thrombosis.

METHODS

We analyzed 266 patients treated at a single institution between 2005 and 2020. Bivariate analysis was conducted using the Mann-Whitney U test and Fisher's exact test. Multivariate analysis was conducted using a logistic regression model. Blood thinning medications investigated included aspirin, warfarin, heparin, apixaban, rivaroxaban, and other novel oral anticoagulants (NOACs). A symptomatic SSS thrombosis was defined as a radiographically apparent thrombosis with new headaches, seizures, altered sensorium, or neurological deficits.

RESULTS

Our patient cohort was majority female (67.3%) with a mean age ([Formula: see text] SD) of 58.82 [Formula: see text] 13.04 years. A total of 15 (5.6%) patients developed postoperative SSS thrombosis and 5 (1.9%) were symptomatic; 2 (0.8%) symptomatic patients received anticoagulation. None of these 15 patients developed cerebrovascular complications following observation or anticoagulative treatment of asymptomatic SSS thrombosis. While incidence of any other postoperative complications was significantly associated with SSS thrombosis in bivariate analysis (p = 0.015), this association was no longer observed in multivariate analysis (OR = 2.15, p = 0.16) when controlling for patient age, sex, and anatomical location of the tumor along the SSS.

CONCLUSIONS

Our single-institution study examining the incidence of SSS thrombosis and associated risk factors highlights the need for further research efforts better prognosticate this adverse outcome. Conservative management may represent a viable treatment strategy for patients with SSS thrombosis.

Which medical schools produce the most neurosurgery residents? An analysis of the 2014-2020 cohort

OBJECTIVE

In this study, the authors sought to determine which US medical schools have produced the most neurosurgery residents and to evaluate potential associations between recruitment and medical school characteristics.

METHODS

Demographic and bibliometric characteristics were collected for 1572 residents in US-based and Accreditation Council for Graduate Medical Education (ACGME)-accredited neurosurgery programs over the 2014 to 2020 match period using publicly available websites. US medical school characteristics were collected, including class size, presence of a home neurosurgery program, number of clinical neurosurgery faculty, research funding, presence of a neurosurgery interest group, and a top 10 ranking via U.S. News & World Report or Doximity. Correlations and associations were then evaluated using Pearson's correlation coefficient (PCC), independent-samples t-test, and univariable or stepwise multivariable linear regression, as appropriate.

RESULTS

Vanderbilt University produced the most neurosurgery residents as a percentage of medical graduates at 3.799%. Case Western Reserve University produced the greatest absolute number of neurosurgery residents (n = 40). The following factors were shown to be associated with a higher mean percentage of graduates entering neurosurgery: number of clinical neurosurgery faculty (PCC 0.509, p < 0.001), presence of a neurosurgery interest group (1.022% ± 0.737% vs 0.351% ± 0.327%, p < 0.001) or home neurosurgery program (1.169% ± 0.766% vs 0.428% ± 0.327%, p < 0.001), allopathic compared with osteopathic school (0.976% ± 0.719% vs 0.232% ± 0.272%, p < 0.001), U.S. News top 10 ranking for neurology and neurosurgery (1.923% ± 0.924% vs 0.757% ± 0.607%, p < 0.001), Doximity top 10 residency program ranking (1.715% ± 0.803% vs 0.814% ± 0.688%, p < 0.001), and amount of NIH funding (PCC 0.528, p < 0.001).

CONCLUSIONS

The results of this study have delineated which medical schools produced the most neurosurgery residents currently in training, and the most important independent factors predicting the percentage of graduates entering neurosurgery and the preresidency h-index.

Disulfiram and copper combination therapy targets NPL4, cancer stem cells and extends survival in a medulloblastoma model

Background

Medulloblastoma (MB) is the most common brain malignancy in children, and is still responsible for significant mortality and morbidity. The aim of this study was to assess the safety and efficacy of Disulfiram (DSF), an FDA-approved inhibitor of Aldehyde-Dehydrogenase (ALDH), and Copper (Cu⁺⁺) in human SSH-driven and Group 3 MB. The molecular mechanisms, effect on cancer-stem-cells (CSC) and DNA damage were investigated in xenograft models.

Methods

The cytotoxic and anti-CSC effects of DSF/Cu⁺⁺ were evaluated with clonogenic assays, flow-cytometry, immunofluorescence, western-blotting. ONS76, UW228 (SHH-driven with Tp53m), D425med, D283 and D341 (Group 3) cell-lines were used. In vivo survival and nuclear protein localization protein-4 (NPL4), Ki67, Cleaved-Caspase-3, GFAP and NeuN expression were assessed in two Group 3 MB xenografts with immunohistochemistry and western-blotting.

Results

Significant in vitro cytotoxicity was demonstrated at nanomolar concentrations. DSF/Cu⁺⁺ induced cell-death through NPL4 accumulation in cell-nucleus and buildup of poly-ubiquitylated proteins. Flow-cytometry demonstrated a significant decrease in ALDH⁺, Nestin⁺ and CD133⁺ following treatment, anti-CSC effect was confirmed in vitro and in vivo. DSF/Cu⁺⁺ prolonged survival, and increased nuclear NPL4 expression in vivo.

Conclusions

Our data suggest that this combination may serve as a novel treatment, as monotherapy or in combination with existing therapies, for aggressive subtypes of pediatric MB.

The safety and efficacy of dexamethasone in the perioperative management of glioma patients

OBJECTIVE

In this single-institution retrospective cohort study, the authors evaluated the effect of dexamethasone on postoperative complications and overall survival in patients with glioma undergoing resection.

METHODS

A total of 435 patients who underwent resection of a primary glioma were included in this retrospective cohort study. The inclusion criterion was all patients who underwent resection of a primary glioma at a tertiary medical center between 2014 and 2019.

RESULTS

The use of both pre- and postoperative dexamethasone demonstrated a trend toward the development of postoperative wound infections (3% vs 0% in single use or no use, p = 0.082). No association was detected between dexamethasone use and the development of new-onset hyperglycemia (p = 0.149). On multivariable Cox proportional hazards analysis, dexamethasone use was associated with a greater hazard of death (overall p = 0.017); this effect was most pronounced for preoperative (only) dexamethasone use (hazard ratio 3.0, p = 0.062).

CONCLUSIONS

Combined pre- and postoperative dexamethasone use may increase the risk of postoperative wound infection, and dexamethasone use, specifically preoperative use, may negatively impact survival. These findings highlight the potential for serious negative consequences with dexamethasone use.

Combination checkpoint therapy with anti-PD-1 and anti-BTLA results in a synergistic therapeutic effect against murine glioblastoma

Clinical trials involving anti-programmed cell death protein-1 (anti-PD-1) failed to demonstrate improved overall survival in glioblastoma (GBM) patients. This may be due to the expression of alternative checkpoints such as B- and T- lymphocyte attenuator (BTLA) on several immune cell types including regulatory T cells. Murine GBM models indicate that there is significant upregulation of BTLA in the tumor microenvironment (TME) with associated T cell exhaustion. We investigate the use of antibodies against BTLA and PD-1 on reversing immunosuppression and increasing long-term survival in a murine GBM model. C57BL/6 J mice were implanted with the murine glioma cell line GL261 and randomized into 4 arms: (i) control, (ii) anti-PD-1, (iii) anti-BTLA, and (iv) anti-PD-1 + anti-BTLA. Kaplan–Meier curves were generated for all arms. Flow cytometric analysis of blood and brains were done on days 11 and 16 post-tumor implantation. Tumor-bearing mice treated with a combination of anti-PD-1 and anti-BTLA therapy experienced improved overall long-term survival (60%) compared to anti-PD-1 (20%) or anti-BTLA (0%) alone (P = .003). Compared to monotherapy with anti-PD-1, mice treated with combination therapy also demonstrated increased expression of CD4+ IFN-γ (P < .0001) and CD8+ IFN-γ (P = .0365), as well as decreased levels of CD4+ FoxP3+ regulatory T cells on day 16 in the brain (P = .0136). This is the first preclinical investigation into the effects of combination checkpoint blockade with anti-PD-1 and anti-BTLA treatment in GBM. We also show a direct effect on activated immune cell populations such as CD4+ and CD8 + T cells and immunosuppressive regulatory T cells through this combination therapy.

Targeting of cyclin-dependent kinases in atypical teratoid rhabdoid tumors with multikinase inhibitor TG02

OBJECTIVE

Atypical teratoid rhabdoid tumors (ATRTs) are aggressive pediatric brain tumors with no current standard of care and an estimated median patient survival of 12 to 18 months. Previous genetic analyses have implicated cyclin D1 and enhancer of zeste homolog 2 (EZH2), a histone methyltransferase that is implicated in many cancers, as key drivers of tumorigenicity in ATRTs. Since the effects of EZH2 and cyclin D1 are facilitated by a host of cyclin-dependent kinases (CDKs), the authors sought to investigate the potential therapeutic effects of targeting CDKs in ATRTs with the multi-CDK inhibitor, TG02.

METHODS

Human ATRT cell lines BT12, BT37, CHLA05, and CHLA06 were selected for investigation. The effects of TG02 on cell viability, proliferation, clonogenicity, and apoptosis were assessed via Cell Counting Kit-8 assays, cell counting, clonogenic assays, and flow cytometry, respectively. Similar methods were used to determine the effects of TG02 combined with radiation therapy (RT) or cisplatin. Synergism indices for TG02-cisplatin combination therapy were calculated using CompuSyn software.

RESULTS

TG02 was observed to significantly impair ATRT cell growth in vitro by limiting cell proliferation and clonogenicity, and by inducing apoptosis. TG02 inhibited ATRT cell proliferation and decreased cell viability in a dose-dependent manner with nanomolar half maximal effective concentration (EC50) values (BT12, 207.0 nM; BT37, 127.8 nM; CHLA05, 29.7 nM; CHLA06, 18.7 nM). TG02 (150 nM) dramatically increased the proportion of apoptotic ATRT cells 72 hours posttreatment (TG02 8.50% vs control 1.52% apoptotic cells in BT12, p < 0.0001; TG02 70.07% vs control 15.36%, p < 0.0001). Combination therapy studies revealed that TG02 acted as a potent radiosensitizer in ATRT cells (BT12 surviving fraction, RT 51.2% vs RT + TG02 21.7%). Finally, CompuSyn analysis demonstrated that TG02 acted synergistically with cisplatin against ATRT cells at virtually all therapeutic doses. These findings were consistent in cell lines that cover all three molecular subgroups of ATRTs.

CONCLUSIONS

The results of this investigation have established that TG02 is an effective therapeutic against ATRTs in vitro. Given the lack of standard therapy for ATRTs, these findings help fill an unmet need and support further study of TG02 as a potential therapeutic option for patients with this deadly disease.

Patient-Specific Factors Drive Intensive Care Unit and Total Hospital Length of Stay in Operative Patients with Brain Tumor

BACKGROUND

Hospital length of stay (LOS) is an important cost driver in neurosurgery. Broader surgical literature has shown that patient-related factors, including comorbidities, and procedure-related factors, such surgeon experience, may be associated with LOS. Because value optimization strategies may be targeted toward either domain, this study investigated the contributions of patient-related and procedure-related factors in predicting prolonged intensive care unit LOS (iLOS) and total hospital LOS (tLOS).

METHODS

Data for adult patients undergoing brain tumor surgery (2017-2019) were collected. Bivariate analyses for iLOS and tLOS were performed using the Mann-Whitney U test and Fisher exact test. Variables associated with either outcome with P < 0.10 were included in patient-only, procedure-only, and patient+procedure factor multivariate linear regression models. Model discrimination was quantified using C-statistics.

RESULTS

Our 654 patients had a mean age of 57.54 years (standard deviation, ± 14.34 years). For iLOS, the patient-only model significantly outperformed the procedure-only model (P < 0.0001) and performed similarly to the patient+procedure model (P = 0.50). Other than tumor diagnosis, 5-Factor Modified Frailty Index score was the only factor associated with iLOS (P < 0.001) and tLOS (P < 0.001) on multivariate analysis. When predicting prolonged tLOS, the patient-only model significantly outperformed the procedure-only model (P < 0.0001), and performed similarly to patient+procedure models (P = 0.49).

CONCLUSIONS

Patient-specific factors are the main drivers of prolonged iLOS and tLOS among patients with brain tumor. Frailty was significantly associated with both iLOS and tLOS on multivariate analysis. Efforts to improve care value should focus on strategies to optimize patient status, such as prehabilitation and enhanced recovery after surgery.

Abstract 2716: P-selectin axis plays a key role in microglia immunophenotype and glioblastoma progression

Glioblastoma (GB) is an aggressive type of brain cancer with high mortality rate. It is a highly angiogenic tumor exhibiting an extremely invasive nature. As such, its brain microenvironment plays a crucial role in its progression. Microglia are the brain resident immune cells which have been shown to facilitate GB cell invasion and immune suppression. The mechanism by which GB cells alter microglia behavior is yet to be fully understood. One proposed mechanism involves adhesion molecules such as the Selectins family of proteins which are expressed on the surface of endothelial and immune cells and are involved in immune modulation and cancer immunity. We have previously shown that P-Selectin (SELP) is expressed by GB cells. Here, we investigated the factional role of SELP in GB-microglia interactions. First, we found that microglia cells facilitate the expression and secretion of SELP by GB cells, and that GB cells facilitate the expression of P-Selectin ligand by microglia. We then showed that SELP mediates microglia-enhanced GB invasion and proliferation in 2D and 3D in vitro models and has a role in microglia activation state. These findings were validated in vivo, showing that inhibition or downregulation of SELP leads to reduced tumor growth, increased overall survival and improved immune response. Single-Cells RNA-seq analysis of the tumors revealed an increase in pro-inflammatory microglia signature, reduction in cancer cell tumorigenesis potential and improved T cell activation. Our results indicated that SELP has an important role in GB progression and microenvironment activation. This work can improve our understanding of tumor-associated microglia function and the mechanisms by which GB cells suppress the immune system and invade the brain tissue.

Citation Format: Eilam Yeini, Paula Ofek, Sabina Pozzi, Nitzan Albeck, Dikla Ben-Shushan, Galia Tiram, Sapir Golan, Ron Kleiner, Ron Sheinin, Shlomit Reich-Zeliger, Rachel Grossman, Zvi Ram, Henry Brem, Thomas Hyde, Prerna Magod, Dinorah Friedmann-Morvinski, Asaf Madi, Ronit Satchi-Fainaro. P-selectin axis plays a key role in microglia immunophenotype and glioblastoma progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2716.

Captopril inhibits Matrix Metalloproteinase-2 and extends survival as a temozolomide adjuvant in an intracranial gliosarcoma model

BACKGROUND

Captopril is a well-characterized, FDA-approved drug that has demonstrated promise as a repurposed oncology therapeutic. Captopril's known anti-cancer effects include inhibition of Matrix Metalloproteinase-2 (MMP-2), an endopeptidase which selectively breaks down the extracellular matrix to promote cell migration. MMP-2 is a known therapeutic target in gliomas, tumors with significant clinical need. Using an aggressive gliosarcoma model, we assessed captopril's effects on MMP-2 expression in vitro and in vivo as well as its efficacy as an adjuvant in combination therapy regimens in vivo.

METHODS

Following captopril treatment, MMP-2 protein expression and migratory capabilities of 9 L gliosarcoma cells were assessed in vitro via western blots and scratch wound assays, respectively. Rats were intracranially implanted with 9 L gliosarcoma tumors, and survival was assessed in the following groups: control; captopril (30 mg/kg/day); temozolomide (TMZ) (50 mg/kg/day), and captopril+TMZ. In vivo experiments were accompanied by immunohistochemistry for MMP-2 from brain tissue.

RESULTS

In vitro, captopril decreased MMP-2 protein expression and reduced migratory capacity in 9 L gliosarcoma cells. In a gliosarcoma animal model, captopril decreased MMP-2 protein expression and extended survival as a TMZ adjuvant relative to untreated controls, captopril monotherapy, and TMZ monotherapy groups (27.5 versus 14 (p < 0.001), 16 (p < 0.001), and 23 (p = 0.018) days, respectively).

CONCLUSIONS

Captopril decreases gliosarcoma cell migration, which may be mediated by reduction in MMP-2 protein expression. Captopril provided a survival advantage as a TMZ adjuvant in a rat intracranial gliosarcoma model. Captopril may represent a promising potential adjuvant to TMZ therapy in gliosarcoma as a modulator of the MMP-2 pathway.

Predictors of Academic Neurosurgical Career Trajectory among International Medical Graduates Training Within the United States

BACKGROUND

Within the literature, there has been limited research tracking the career trajectories of international medical graduates (IMGs) following residency training.

OBJECTIVE

To compare the characteristics of IMG and US medical school graduate (USMG) neurosurgeons holding academic positions in the United States and also analyze factors that influence IMG career trajectories following US-based residency training.

METHODS

We collected data on 243 IMGs and 2506 USMGs who graduated from Accreditation Council for Graduate Medical Education (ACGME)-accredited neurosurgery residency programs. We assessed for significant differences between cohorts, and a logistic regression model was used for the outcome of academic career trajectory.

RESULTS

Among the 2749 neurosurgeons in our study, IMGs were more likely to pursue academic neurosurgery careers relative to USMGs (59.7% vs 51.1%; P = .011) and were also more likely to complete a research fellowship before beginning residency (odds ratio [OR] = 9.19; P < .0001). Among current US academic neurosurgeons, USMGs had significantly higher pre-residency h-indices relative to IMGs (1.23 vs 1.01; P < .0001) with no significant differences between cohorts when comparing h-indices during (USMG = 5.02, IMG = 4.80; P = .67) or after (USMG = 14.05, IMG = 13.90; P = .72) residency. Completion of a post-residency clinical fellowship was the only factor independently associated with an academic career trajectory among IMGs (OR = 1.73, P = .046).

CONCLUSION

Our study suggests that while IMGs begin their US residency training with different research backgrounds and achievements relative to USMG counterparts, they attain similar levels of academic productivity following residency. Furthermore, IMGs are more likely to pursue academic careers relative to USMGs. Our work may be useful for better understanding IMG career trajectories following US-based neurosurgery residency training.

PD-1+ Monocytes Mediate Cerebral Vasospasm Following Subarachnoid Hemorrhage

BACKGROUND

Cerebral vasospasm is a major source of morbidity and mortality following aneurysm rupture and has limited treatment options.

OBJECTIVE

To evaluate the role of programmed death-1 (PD-1) in cerebral vasospasm.

METHODS

Endovascular internal carotid artery perforation (ICAp) was used to induce cerebral vasospasm in mice. To evaluate the therapeutic potential of targeting PD-1, programmed death ligand-1 (PD-L1) was administered 1 h after ICAp and vasospasm was measured histologically at the level of the ICA bifurcation bilaterally. PD-1 expressing immune cell populations were evaluated by flow cytometry. To correlate these findings to patients and evaluate the potential of PD-1 as a biomarker, monocytes were isolated from the peripheral blood and analyzed by flow cytometry in a cohort of patients with ruptured cerebral aneurysms. The daily frequency of PD-1+ monocytes in the peripheral blood was correlated to transcranial Doppler velocities as well as clinical and radiographic vasospasm.

RESULTS

We found that PD-L1 administration prevented cerebral vasospasm by inhibiting ingress of activated Ly6c+ and CCR2+ monocytes into the brain. Human correlative studies confirmed the presence of PD-1+ monocytes in the peripheral blood of patients with ruptured aneurysms and the frequency of these cells corresponded with cerebral blood flow velocities and clinical vasospasm.

CONCLUSION

Our results identify PD-1+ monocytes as mediators of cerebral vasospasm and support PD-1 agonism as a novel therapeutic strategy.

P-selectin axis plays a key role in microglia immunophenotype and glioblastoma progression

Glioblastoma (GB) is a highly invasive type of brain cancer exhibiting poor prognosis. As such, its microenvironment plays a crucial role in its progression. Among the brain stromal cells, the microglia were shown to facilitate GB invasion and immunosuppression. However, the reciprocal mechanisms by which GB cells alter microglia/macrophages behavior are not fully understood. We propose that these mechanisms involve adhesion molecules such as the Selectins family. These proteins are involved in immune modulation and cancer immunity. We show that P-selectin mediates microglia-enhanced GB proliferation and invasion by altering microglia/macrophages activation state. We demonstrate these findings by pharmacological and molecular inhibition of P-selectin which leads to reduced tumor growth and increased survival in GB mouse models. Our work sheds light on tumor-associated microglia/macrophage function and the mechanisms by which GB cells suppress the immune system and invade the brain, paving the way to exploit P-selectin as a target for GB therapy.

Preclinical efficacy of ribavirin in SHH and group 3 medulloblastoma

OBJECTIVE

Medulloblastoma, the most common pediatric brain malignancy, has Sonic Hedgehog (SHH) and group 3 (Myc driven) subtypes that are associated with the activity of eukaryotic initiation factor 4E (eIF4E), a critical mediator of translation, and enhancer of zeste homolog 2 (EZH2), a histone methyltransferase and master regulator of transcription. Recent drug repurposing efforts in multiple solid and hematologic malignancies have demonstrated that eIF4E and EZH2 are both pharmacologically inhibited by the FDA-approved antiviral drug ribavirin. Given the molecular overlap between medulloblastoma biology and known ribavirin activity, the authors investigated the preclinical efficacy of repurposing ribavirin as a targeted therapeutic in cell and animal models of medulloblastoma.

METHODS

Multiple in vitro assays were performed using human ONS-76 (a primitive SHH model) and D425 (an aggressive group 3 model) cells. The impacts of ribavirin on cellular growth, death, migration, and invasion were quantified using proliferation and Cell Counting Kit-8 (CCK-8) assays, flow cytometry with annexin V (AnnV) staining, scratch wound assays, and Matrigel invasion chambers, respectively. Survival following daily ribavirin treatment (100 mg/kg) was assessed in vivo in immunodeficient mice intracranially implanted with D425 cells.

RESULTS

Compared to controls, ribavirin treatment led to a significant reduction in medulloblastoma cell growth (ONS-76 proliferation assay, p = 0.0001; D425 CCK-8 assay, p < 0.0001) and a significant increase in cell death (flow cytometry for AnnV, ONS-76, p = 0.0010; D425, p = 0.0284). In ONS-76 cells, compared to controls, ribavirin significantly decreased cell migration and invasion (Matrigel invasion chamber assay, p = 0.0012). In vivo, ribavirin significantly extended survival in an aggressive group 3 medulloblastoma mouse model compared to vehicle-treated controls (p = 0.0004).

CONCLUSIONS

The authors demonstrate that ribavirin, a clinically used drug known to inhibit eIF4E and EZH2, has significant antitumor effects in multiple preclinical models of medulloblastoma, including an aggressive group 3 animal model. Ribavirin may represent a promising targeted therapeutic in medulloblastoma.

Automatic detection of cotton balls during brain surgery: Where deep learning meets ultrasound imaging to tackle foreign objects

Cotton balls are a versatile and efficient tool commonly used in neurosurgical procedures to absorb fluids and manipulate delicate tissues. However, the use of cotton balls is accompanied by the risk of accidental retention in the brain after surgery. Retained cotton balls can lead to dangerous immune responses and potential complications, such as adhesions and textilomas. In a previous study, we showed that ultrasound can be safely used to detect cotton balls in the operating area due to the distinct acoustic properties of cotton compared with the acoustic properties of surrounding tissue. In this study, we enhance the experimental setup using a 3D-printed custom depth box and a Butterfly IQ handheld ultrasound probe. Cotton balls were placed in variety of positions to evaluate size and depth detectability limits. Recorded images were then analyzed using a novel algorithm that implements recently released YOLOv4, a state-of-the-art, real-time object recognition system. As per the radiologists' opinion, the algorithm was able to detect the cotton ball correctly 61% of the time, at approximately 32 FPS. The algorithm could accurately detect cotton balls up to 5mm in diameter, which corresponds to the size of surgical balls used by neurosurgeons, making the algorithm a promising candidate for regular intraoperative use.

Development of new brain metastases in triple negative breast cancer

BACKGROUND

Brain metastases are common in patients with breast cancer, and those with triple negative status have an even higher risk. Triple negative status is currently not considered when managing brain metastases.

OBJECTIVE

To determine whether triple negative breast cancer (TNBC) patients with brain metastases have a higher burden of intracranial disease and whether WBRT has a survival benefit in this cohort of patients.

METHODS

We conducted a retrospective cohort study with 85 patients meeting the inclusion criteria.

RESULTS

25% of patients had TNBC. 95% of the patients in this study received SRS and 48% received WBRT. The average number of new brain metastases from time of initial brain imaging to radiation therapy was 0.67 ± 1.1 in the non-TNBC status patients and 2.6 ± 3.7 in the triple negative status patients (p = 0.001). A cox proportional hazards model showed that WBRT does not significantly affect overall survival in patients with TNBC (HR 1.48; 95% CI 0.47-4.67; p = 0.50).

CONCLUSION

Our findings highlight the highly aggressive intracranial nature of TNBC. The rate of new brain metastasis formation is higher in TNBC patients compared to non-TNBC patients. Furthermore, there is no survival benefit for WBRT in TNBC patients. These findings are relevant for clinicians planning brain radiation for TNBC patients as they may find more brain metastases at the time of brain radiation than they anticipated based on initial brain imaging.

Retraction: Ghali MGZ, et al. Mechanisms underlying the generation of autonomorespiratory coupling amongst the respiratory central pattern generator, sympathetic oscillators, and cardiovagal premotoneurons. Journal of Integrative Neuroscience. 2020; 19: 521-560

No abstract present.