Robot-Assisted Stereotactic Biopsy of Diffuse Intrinsic Pontine Glioma: A Single-Center Experience

Safety and Technical Efficacy of Pediatric Brainstem Biopsies: An Updated Meta-Analysis of 1000+ Children

BACKGROUND

Brainstem tumors represent ∼10% of pediatric brain tumors, ∼80% of these are diffuse midline glioma. Given invariably poor prognosis in diffuse midline glioma, there continues to be immense variation worldwide in performing biopsy of these lesions. Several contemporary studies in recent years have provided new data to elucidate the safety profile of biopsy and an updated meta-analysis is thus indicated.

METHODS

We found 29 studies of pediatric brainstem biopsy in the last 20 years (2003-2023, 1002 children). We applied meta-analysis of proportions using a random-effects model to generate point estimates, confidence intervals, and measures of heterogeneity.

RESULTS

Eighty-seven percent of procedures were stereotactic needle biopsies (of these, 62% with a frame, 14% without frame, and 24% robotic.) Biopsy resulted in a histological diagnosis ("technical yield") in 96.8% of cases (95% CI 95.4-98.2). Temporary complications were seen in 6% (95 CI 4-8), with the most common neurological complications being 1) cranial nerve dysfunction, 2) worsening or new ataxia, and 3) limb weakness. Permanent complications (excluding death) were seen in 1% (95% CI 0.5-2), most commonly including cranial nerve dysfunction and limb weakness. Five deaths were reported in the entire pooled cohort of 1002 children (0.5%).

CONCLUSIONS

When counseling families on the merits of brainstem biopsy in children, it is reasonable to state that permanent morbidity is rare (<2%). If biopsy is performed specifically to facilitate enrollment in clinical trials requiring a molecular diagnosis, the risks of biopsy outlined here should be weighed against potential benefits of trial enrollment.

The Landscape of Pediatric High-Grade Gliomas: The Virtues and Pitfalls of Pre-Clinical Models

Pediatric high-grade gliomas (pHGG) are malignant and usually fatal central nervous system (CNS) WHO Grade 4 tumors. The majority of pHGG consist of diffuse midline gliomas (DMG), H3.3 or H3.1 K27 altered, or diffuse hemispheric gliomas (DHG) (H3.3 G34-mutant). Due to diffuse tumor infiltration of eloquent brain areas, especially for DMG, surgery has often been limited and chemotherapy has not been effective, leaving fractionated radiation to the involved field as the current standard of care. pHGG has only been classified as molecularly distinct from adult HGG since 2012 through Next-Generation sequencing approaches, which have shown pHGG to be epigenetically regulated and specific tumor sub-types to be representative of dysregulated differentiating cells. To translate discovery research into novel therapies, improved pre-clinical models that more adequately represent the tumor biology of pHGG are required. This review will summarize the molecular characteristics of different pHGG sub-types, with a specific focus on histone K27M mutations and the dysregulated gene expression profiles arising from these mutations. Current and emerging pre-clinical models for pHGG will be discussed, including commonly used patient-derived cell lines and in vivo modeling techniques, encompassing patient-derived xenograft murine models and genetically engineered mouse models (GEMMs). Lastly, emerging techniques to model CNS tumors within a human brain environment using brain organoids through co-culture will be explored. As models that more reliably represent pHGG continue to be developed, targetable biological and genetic vulnerabilities in the disease will be more rapidly identified, leading to better treatments and improved clinical outcomes.

Robotic alignment system Cirq (Brainlab) for navigated brain tumor biopsies in children

INTRODUCTION

The Cirq robotic alignment system (Brainlab, Munich, Germany) is a manually adjustable electronic arm with a robotic alignment module on its distal end, enabling the neurosurgeon to automatically and accurately align surgical instruments to a preoperatively planned trajectory. In this study, we share our first experiences and results using Cirq for intracranial tumor biopsy in children.

METHODS

From May 2021 until October 2022, all consecutive patients that underwent a brain tumor biopsy using Cirq were included and compared to a historical cohort of patients biopsied with the non-robotic system Varioguide (Brainlab, Munich, Germany). Patient-related data, tumor-related data, and surgery-related data were collected. Registration accuracy was calculated for different patient-to-image registration methods. Pre- and postoperative images were fused, and entry error, target error, and angulation error were calculated.

RESULTS

Thirty-seven patients, aged 1-19 years, were included (14 with Cirq and 23 with Varioguide). An integrated histopathological and molecular diagnosis was acquired in all cases. Patient-to-image registration was significantly more accurate when based on bone screw fiducials combined with intraoperative CT, as compared to surface matching or skin fiducials. The target error (Euclidian distance) was 5.3 mm for Cirq as compared to 8.3 mm for Varioguide, but this was not statistically significant. Entry error and angulation error were also not significantly different between both groups.

CONCLUSION

Intracranial biopsy with the Cirq robotic system is feasible and safe, and its accuracy does not differ from the Varioguide system.

Surgical Characteristics of Intracranial Biopsy Using a Frameless Stereotactic Robotic Platform: A Single-Center Experience

BACKGROUND AND OBJECTIVES

Cranial robotics are a burgeoning field of neurosurgery. To date, all cranial robotic systems described have been computerized, arm-based instruments that take up significant space in the operating room. The Medtronic Stealth Autoguide robot has a smaller operating room footprint and offers multiaxial, frame-based surgical targeting. The authors set out to define the surgical characteristics of a novel robotic platform for brain biopsy in a large patient cohort.

METHODS

Patients who underwent stereotactic biopsy using the Stealth Autoguide cranial robotic platform from July 2020 to March 2023 were included in this study. Clinical, surgical, and histological data were collected and analyzed.

RESULTS

Ninety-six consecutive patients (50 female, 46 male) were included. The mean age at biopsy was 53.7 ± 18.0 years. The mean target depth was 68.2 ± 15.3 mm. The biopsy diagnostic tissue acquisition rate was 100%. The mean time from incision to biopsy tissue acquisition was 15.4 ± 9.9 minutes. Target lesions were located throughout the brain: in the frontal lobe (n = 32, 33.3%), parietal lobe (n = 21, 21.9%), temporal lobe (n = 22, 22.9%), deep brain nuclei/thalamus (n = 13, 13.5%), cerebellum (n = 7, 7.3%), and brainstem (n = 1, 1.0%). Most cases were gliomas (n = 75, 78.2%). Patients were discharged home on postoperative day 0 or 1 in 62.5% of cases. A total of 7 patients developed postoperative complications (7.2%).

CONCLUSION

This cranial robotic platform can be used for efficient, safe, and accurate cranial biopsies that allow for reliable diagnosis of intracranial pathology in a minimally invasive setting.

Clinical outcomes of stereotactic biopsy on children with pontine diffuse midline glioma

INTRODUCTION

Diffuse midline glioma (DMG) of the pons occurs in pediatric patients and carries a dismal prognosis. Biopsy is not necessary for diagnosis but provides information, particularly H3K27M status, with prognostic implications. Additionally, biopsy information may open therapeutic options such as clinical trials that require mutation status. Therefore, we sought to assess the safety of surgical biopsy in DMG patients as well as its potential impact on clinical course.

METHODS

Retrospective analysis of patients who were radiographically and clinically diagnosed with pontine DMG in the last 5 years was performed. We assessed demographic, clinical, radiographic, surgical, and follow-up data.

RESULTS

25 patients were included; 18 (72%) underwent biopsy while 7 (28%) declined. 12 biopsies (67%) were performed with robotic arm and 5 (27%) with frameless stereotaxy. Three biopsied patients (17%) experienced new post-operative neurologic deficits (1 facial palsy, 1 VI nerve palsy and 1 ataxia) that all resolved at 2-week follow-up. All biopsies yielded diagnostic tissue. Fourteen patients (78%) had H3K27M mutation. Median OS for H3K27M patients was 10 months compared to 11 months in the wild-type patients (p = 0.30, log-rank test). Median OS for patients enrolled in clinical trials was 12 months compared to 8 months for non-trial patients (p = 0.076).

CONCLUSION

In our series, stereotactic pontine DMG biopsies did not carry any permanent deficit or complication and yielded diagnostic tissue in all patients. Similar post-operative course was observed in both robot-assisted and frameless stereotactic approaches. There was no significant difference in survival based on mutation status or clinical trial enrollment.

A Comparison of the Safety, Efficacy, and Accuracy of Frame-Based versus Remebot Robot-Assisted Stereotactic Systems for Biopsy of Brainstem Tumors

BACKGROUND

Brainstem tumors are rare and extremely heterogeneous and present significant challenges in surgical treatment. Thus, biopsies often set the foundation for the diagnosis of brainstem tumors. Multimodal, image-guided, robot-assisted frameless stereotactic biopsies are increasingly popular in neurosurgery centers. This study aimed to compare the safety, efficacy, and duration of the Remebot robot-assisted (Remebot) frameless brainstem tumor biopsy versus those of frame-based stereotactic biopsy.

METHOD

A retrospective analysis of 33 patients with brainstem tumors who underwent stereotactic brainstem biopsies in the department of neurosurgery from January 2016 to January 2021 was conducted. The patients were divided into two groups: the Remebot group (n = 22) and the frame-based group (n = 11). The clinical characteristics, trajectory strategy, duration of procedure, diagnostic yielding, histopathological diagnosis, and postoperative complications were retrospectively analyzed and compared between the groups.

RESULTS

More pediatric patients performed Remebot frameless brainstem tumor biopsy than frame-based biopsy, with a mean age of 17.3 ± 18.7 vs. 32.8 ± 17.1 (p = 0.027). The diagnostic yield had no significant difference in the two groups, with the diagnostic yield of frame-based biopsy and Remebot frameless brain biopsy being 90.9% and 95.5%, respectively. The time of the total process was 124.5 min for the frame-based biopsy and 84.7 min for the Remebot frameless brain biopsy (p < 0.001). There were no significant differences with respect to the occurrence of complication or the duration of the operation between the two groups.

CONCLUSION

Remebot frameless stereotactic brainstem biopsy is as safe and efficacious as frame-based stereotactic biopsy. However, Remebot frameless biopsy can reduce the total duration of the procedure and has better application in young pediatric patients. Remebot frameless stereotactic biopsies can be a better option towards the safe and efficient treatment of brainstem tumors.

Pediatric diffuse midline glioma H3K27- altered: A complex clinical and biological landscape behind a neatly defined tumor type

The 2021 World Health Organization Classification of Tumors of the Central Nervous System, Fifth Edition (WHO-CNS5), has strengthened the concept of tumor grade as a combination of histologic features and molecular alterations. The WHO-CNS5 tumor type "Diffuse midline glioma, H3K27-altered," classified within the family of "Pediatric-type diffuse high-grade gliomas," incarnates an ideally perfect integrated diagnosis in which location, histology, and genetics clearly define a specific tumor entity. It tries to evenly characterize a group of neoplasms that occur primarily in children and midline structures and that have a dismal prognosis. Such a well-defined pathological categorization has strongly influenced the pediatric oncology community, leading to the uniform treatment of most cases of H3K27-altered diffuse midline gliomas (DMG), based on the simplification that the mutation overrides the histological, radiological, and clinical characteristics of such tumors. Indeed, multiple studies have described pediatric H3K27-altered DMG as incurable tumors. However, in biology and clinical practice, exceptions are frequent and complexity is the rule. First of all, H3K27 mutations have also been found in non-diffuse gliomas. On the other hand, a minority of DMGs are H3K27 wild-type but have a similarly poor prognosis. Furthermore, adult-type tumors may rarely occur in children, and differences in prognosis have emerged between adult and pediatric H3K27-altered DMGs. As well, tumor location can determine differences in the outcome: patients with thalamic and spinal DMG have significantly better survival. Finally, other concomitant molecular alterations in H3K27 gliomas have been shown to influence prognosis. So, when such additional mutations are found, which one should we focus on in order to make the correct clinical decision? Our review of the current literature on pediatric diffuse midline H3K27-altered DMG tries to address such questions. Indeed, H3K27 status has become a fundamental supplement to the histological grading of pediatric gliomas; however, it might not be sufficient alone to exhaustively define the complex biological behavior of DMG in children and might not represent an indication for a unique treatment strategy across all patients, irrespective of age, additional molecular alterations, and tumor location.

Robotics in Interventional Radiology: Review of Current and Future Applications

This review is a brief overview of the current status and the potential role of robotics in interventional radiology. Literature published in the last decades, with an emphasis on the last 5 years, was reviewed and the technical developments in robotics and navigational systems using CT-, MR- and US-image guidance were analyzed. Potential benefits and disadvantages of their current and future use were evaluated. The role of fusion imaging modalities and artificial intelligence was analyzed in both percutaneous and endovascular procedures. A few hundred articles describing results of single or several systems were included in our analysis.

Frameless Robotic-Assisted Biopsy of Pediatric Brainstem Lesions: A Systematic Review and Meta-Analysis of Efficacy and Safety

BACKGROUND

Pediatric brainstem lesions are diagnoses that require tissue sampling to advance our understanding of them and their management. Frameless, robot-assisted biopsy of these lesions has emerged as a novel, viable biopsy approach. Correspondingly, the aim of this study was to quantitively and qualitatively summarize the contemporary literature regarding the likelihood of achieving tumor diagnosis and experiencing any postoperative complications.

METHODS

Searches of 7 electronic databases from inception to September 2022 were conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Articles were screened against prespecified criteria. Outcomes were pooled by random-effects meta-analyses of proportions where possible.

RESULTS

A total of 8 cohort studies satisfied all criteria. They described 99 pediatric patients with brainstem lesions in whom frameless, robot-assisted biopsy was involved in their work-up. There were 62 (63%) male and 37 (37%) female patients with a median age of 9 years at time of biopsy. Overall, all patients had sufficient tissue obtained by initial biopsy for evaluation. Pooled estimate of achieving tumor diagnosis was 100% (95% confidence interval [CI] 97%-100%) across all studies with a high degree of certainty. Across all studies, there were no cases of procedure-related mortality. The pooled estimates of transient and permanent complications after biopsy were 10% (95% CI 4%-19%) and 0% (95% CI 0%-2%), respectively, of very low and low degrees of certainty each.

CONCLUSIONS

The contemporary metadata demonstrates the frameless, robot-assisted biopsy of pediatric brainstem lesions is both effective and safe when performed in an experienced setting. Further research is needed to augment robot and automated technologies into workup algorithms.

Targeted therapy for pediatric diffuse intrinsic pontine glioma: a single-center experience

Background:

Diffuse intrinsic pontine glioma (DIPG) is a fatal disease with a median overall survival (OS) of less than 12 months after diagnosis. Radiotherapy (RT) still remains the mainstay treatment. Several other therapeutic strategies have been attempted in the last years without a significant effect on OS. Although radiological imaging is the gold standard for DIPG diagnosis, the urgent need to improve the survival has led to the reconsideration of biopsy with the aim to better understand the molecular profile of DIPG and support personalized treatment.

Methods:

In this study, we present a single-center experience in treating DIPG patients at disease progression combining targeted therapies with standard of care. Biopsy was proposed to all patients at diagnosis or disease progression. First-line treatment included RT and nimotuzumab/vinorelbine or temozolomide. Immunohistochemistry-targeted research included study of mTOR/p-mTOR pathway and BRAFv600E. Molecular analyses included polymerase chain reaction, followed by Sanger sequences and/or next-generation sequencing.

Results:

Based on the molecular profile, targeted therapy was administered in 9 out of 25 patients, while the remaining 16 patients were treated with standard of care. Personalized treatment included inhibition of the PI3K/AKT/mTOR pathway (5/9), PI3K/AKT/mTOR pathway and BRAFv600E (1/9), ACVR1 (2/9) and PDGFRA (1/9); no severe side effects were reported during treatment. Response to treatment was evaluated according to Response Assessment in Pediatric Neuro-Oncology criteria, and the overall response rate within the cohort was 66%. Patients treated with targeted therapies were compared with the control cohort of 16 patients. Clinical and pathological characteristics of the two cohorts were homogeneous. Median OS in the personalized treatment and control cohort was 20.26 and 14.18 months, respectively (p = 0.032). In our experience, the treatment associated with the best OS was everolimus.

Conclusion:

Despite the small simple size of our study, our data suggest a prognostic advantage and a safe profile of targeted therapies in DIPG patients, and we strongly advocate to reconsider the role of biopsy for these patients.

Frameless robot-assisted stereotactic biopsy: an effective and minimally invasive technique for pediatric diffuse intrinsic pontine gliomas

PURPOSE

Diffuse intrinsic pontine gliomas (DIPGs) are prone to high surgical risks, and they could even lead to death due to their specific sites. To determine the value of frameless robot-assisted stereotactic biopsies of DIPGs, when compared it with microsurgical biopsies.

METHODS

We conducted a retrospective study of 71 pediatric patients who underwent biopsies from January 2016 to January 2021. (i) group 1: microsurgical biopsies, and (ii) group 2: frameless robot-assisted stereotactic biopsies. Demographic information, neuroimaging characteristics, pathological diagnoses, operation time, postoperative intensive care unit (ICU) stay time, postoperative hospitalization time, complications, cost, and perioperative mortality rate (POMR) were collected for analyses.

RESULTS

32 Cases underwent microsurgical biopsies (group 1) and 39 cases underwent frameless robot-assisted stereotactic biopsies (group 2). All cases were accurately diagnosed after surgery. There was no significant difference in gender, age, symptom times and tumor volumes between the two groups (p > 0.05); operation time, postoperative ICU, stay time and postoperative hospitalization time were longer in group 1 than in group 2 (p < 0.001); the intraoperative bleeding volumes and cost were higher in group 1 than in group 2 (p < 0.001). Group 1 patients required more perioperative blood transfusion than group 2 (p = 0.001), and the new neurological impairments were more frequent in group 1 than in group 2 (p = 0.003). The POMR was 9.38% (3/32) in group 1 and 0 in group 2 (p = 0.087).

CONCLUSIONS

Frameless robot-assisted stereotactic biopsy was an effective and minimally invasive technique for pediatric DIPGs.

A Comparation Between Frame-Based and Robot-Assisted in Stereotactic Biopsy

Introduction

Frame-based stereotactic biopsy is well-established to play an essential role in neurosurgery. In recent years, different robotic devices have been introduced in neurosurgery centers. This study aimed to compare the SINO surgical robot-assisted frameless brain biopsy with standard frame-based stereotactic biopsy in terms of efficacy, accuracy and complications.

Methods

A retrospective analysis was performed on 151 consecutive patients who underwent stereotactic biopsy at Chongqing Sanbo Jiangling Hospital between August 2017 and December 2021. All patients were divided into the frame-based group (n = 47) and the SINO surgical robot-assisted group (n = 104). The data collected included clinical characteristics, diagnostic yield, operation times, accuracy, and postoperative complications.

Results

There was no significant difference in diagnostic yield between the frame-based group and the SINO surgical robot-assisted group (95.74 vs. 98.08%, p > 0.05). The mean operation time in the SINO surgical robot-assisted group was significantly shorter than in the frame-based group (29.36 ± 13.64 vs. 50.57 ± 41.08 min). The entry point error in the frame-based group was significantly higher than in the robot-assisted group [1.33 ± 0.40 mm (0.47–2.30) vs. 0.92 ± 0.27 mm (0.35–1.65), P < 0.001]. The target point error in the frame-based group was also significantly higher than in the robot-assisted group [1.63 ± 0.41 mm (0.74–2.65) vs. 1.10 ± 0.30 mm (0.69–2.03), P < 0.001]. Finally, there was no significant difference in postoperative complications between the two groups.

Conclusion

Robot-assisted brain biopsy becomes an increasingly mainstream tool in the neurosurgical procedure. The SINO surgical robot-assisted platform is as efficient, accurate and safe as standard frame-based stereotactic biopsy and provides a reasonable alternative to stereotactic biopsy in neurosurgery.

The Role of Stereotactic Frame-Based Biopsy for Brainstem Tumors in the Era of Molecular-Based Diagnosis and Treatment Decisions

Stereotactic frame-based brain tumor biopsy (SFB) is a potent diagnostic tool considering its minimal invasiveness, though its diagnostic power and safety for brainstem lesions remain to be discussed. Here, we aimed to examine the usefulness of SFB for brainstem tumors. Twenty-two patients with brainstem tumors underwent 23 SFBs at our institution during 2002–2021. We retrospectively analyzed patient characteristics, tumor pathology, surgical procedures, and outcomes, including surgery-related complications and the diagnostic value. Seven (32%) tumors were located from the midbrain to the pons, eleven (50%) in the pons only, and four (18%) from the pons to the medulla oblongata. The target lesions were in the middle cerebellar peduncles in sixteen procedures (70%), the cerebellum in four (17%), the inferior cerebellar peduncles in two (9%), and the superior cerebellar peduncles in one (4%). A definitive diagnosis was made in 21 patients (95%) at the first SFB. The diagnoses were glioma in seventeen (77%) cases, primary central nervous system lymphoma in four (18%), and a metastatic brain tumor in one (5%). The postoperative complications (cranial nerve palsy in three [13%] cases, ataxia in one [4%]) were all transient. SFB for brainstem tumors yields a high diagnostic rate with a low risk of morbidity.

Frameless robot-assisted stereotactic biopsies for lesions of the brainstem-a series of 103 consecutive biopsies

PURPOSE

Targeted treatment for brainstem lesions requires above all a precise histopathological and molecular diagnosis. In the current technological era, robot-assisted stereotactic biopsies represent an accurate and safe procedure for tissue diagnosis. We present our center's experience in frameless robot-assisted biopsies for brainstem lesions.

METHODS

We performed a retrospective analysis of all patients benefitting from a frameless robot-guided stereotactic biopsy at our University Hospital, from 2001 to 2017. Patients consented to the use of data and/or images. The NeuroMate® robot (Renishaw™, UK) was used. We report on lesion location, trajectory strategy, histopathological diagnosis and procedure safety.

RESULTS

Our series encompasses 96 patients (103 biopsies) treated during a 17 years period. Mean age at biopsy: 34.0 years (range 1-78). Most common location: pons (62.1%). Transcerebellar approach: 61 procedures (59.2%). Most common diagnoses: diffuse glioma (67.0%), metastases (7.8%) and lymphoma (6.8%). Non conclusive diagnosis: 10 cases (9.7%). After second biopsy this decreased to 4 cases (4.1%). Overall biopsy diagnostic yield: 95.8%. Permanent disability was recorded in 3 patients (2.9%, all adults), while transient complications in 17 patients (17.7%). Four cases of intra-tumoral hematoma were recorded (one case with rapid decline and fatal issue). Adjuvant targeted treatment was performed in 72.9% of patients. Mean follow-up (in the Neurosurgery Department): 2.2 years.

CONCLUSION

Frameless robot-assisted stereotactic biopsies can provide the initial platform towards a safe and accurate management for brainstem lesions, offering a high diagnostic yield with low permanent morbidity.

Glioma Imaging by O-(2-18F-Fluoroethyl)-L-Tyrosine PET and Diffusion-Weighted MRI and Correlation With Molecular Phenotypes, Validated by PET/MR-Guided Biopsies

Gliomas exhibit high intra-tumoral histological and molecular heterogeneity. Introducing stereotactic biopsy, we achieved a superior molecular analysis of glioma using O-(2-18F-fluoroethyl)-L-tyrosine (FET)-positron emission tomography (PET) and diffusion-weighted magnetic resonance imaging (DWI). Patients underwent simultaneous DWI and FET-PET scans. Correlations between biopsy-derived tumor tissue values, such as the tumor-to-background ratio (TBR) and apparent diffusion coefficient (ADC)/exponential ADC (eADC) and histopathological diagnoses and those between relevant genes and TBR and ADC values were determined. Tumor regions with human telomerase reverse transcriptase (hTERT) mutation had higher TBR and lower ADC values. Tumor protein P53 mutation correlated with lower TBR and higher ADC values. α-thalassemia/mental-retardation-syndrome-X-linked gene (ATRX) correlated with higher ADC values. 1p/19q codeletion and epidermal growth factor receptor (EGFR) mutations correlated with lower ADC values. Isocitrate dehydrogenase 1 (IDH1) mutations correlated with higher TBRmean values. No correlation existed between TBRmax/TBRmean/ADC/eADC values and phosphatase and tensin homolog mutations (PTEN) or O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation. Furthermore, TBR/ADC combination had a higher diagnostic accuracy than each single imaging method for high-grade and IDH1-, hTERT-, and EGFR-mutated gliomas. This is the first study establishing the accurate diagnostic criteria for glioma based on FET-PET and DWI.

New Developments in the Pathogenesis, Therapeutic Targeting, and Treatment of H3K27M-Mutant Diffuse Midline Glioma

H3K27M-mutant diffuse midline gliomas (DMGs) are rare childhood central nervous system tumors that carry a dismal prognosis. Thus, innovative treatment approaches are greatly needed to improve clinical outcomes for these patients. Here, we discuss current trends in research of H3K27M-mutant diffuse midline glioma. This review highlights new developments of molecular pathophysiology for these tumors, as they relate to epigenetics and therapeutic targeting. We focus our discussion on combinatorial therapies addressing the inherent complexity of treating H3K27M-mutant diffuse midline gliomas and incorporating recent advances in immunotherapy, molecular biology, genetics, radiation, and stereotaxic surgical diagnostics.

[Diffuse brainstem tumors in children. Tumor biology and hope for a better outcome. Current state of the problem]

Diffuse brainstem tumor is a fatal disease and the main cause of child mortality from neoplasms of central nervous system. So far, no effective therapy has been found for this disease. The authors discuss the modern aspects of clinical data, biology, diagnosis and treatment of patients with diffuse brainstem tumors.

A Bulk Retrospective Study of Robot-Assisted Stereotactic Biopsies of Intracranial Lesions Guided by Videometric Tracker

Background: Biopsies play an important role in the diagnosis of intracranial lesions, and robot-assisted procedures are increasingly common in neurosurgery centers. This research investigates the diagnoses, complications, and technology yield of 700 robotic frameless intracranial stereotactic biopsies conducted with the Remebot system. Method: This research considered 700 robotic biopsies performed between 2016 and 2020 by surgeons from the Department of Functional Neurosurgery in Beijing's Tiantan Hospital. The data collected included histological diagnoses, postoperative complications, operation times, and the accuracy of robotic manipulation. Results: Among the 700 surgeries, the positive rate of the biopsies was 98.2%. The most common histological diagnoses were gliomas, which accounted for 62.7% of cases (439/700), followed by lymphoma and germinoma, which accounted for 18.7% (131/700) and 7.6% (53/700). Bleeding was found in 14 patients (2%) by post-operation computed tomography scans. A total of 29 (4.14%) patients had clinical impairments after the operation, and 9 (1.29%) experienced epilepsy during the operation. The post-biopsy mortality rate was 0.43%. Operation time-from marking the cranial point to suturing the skin-was 16.78 ± 3.31 min (range 12-26 min). The target error was 1.13 ± 0.30 mm, and the entry point error was 0.99 ± 0.24 mm. Conclusion: A robot-assisted frameless intracranial stereotactic biopsy guided by a videometric tracker is an efficient, safe, and accurate method for biopsies.

Robotic guidance platform for laser interstitial thermal ablation and stereotactic needle biopsies: a single center experience

While laser ablation has become an increasingly important tool in the neurosurgical oncologist's armamentarium, deep seated lesions, and those located near critical structures require utmost accuracy during stereotactic laser catheter placement. Robotic devices have evolved significantly over the past two decades becoming an accurate and safe tool for stereotactic neurosurgery. Here, we present our single center experience with the MedTech ROSA ONE Brain robot for robotic guidance in laser interstitial thermal therapy (LITT) and stereotactic biopsies. We retrospectively analyzed the first 70 consecutive patients treated with ROSA device at a single academic medical center. Forty-three patients received needle biopsy immediately followed by LITT with the catheter placed with robotic guidance and 27 received stereotactic needle biopsy alone. All the procedures were performed frameless with skull bone fiducials for registration. We report data regarding intraoperative details, mortality and morbidity, diagnostic yield and lesion characteristics on MRI. Also, we describe the surgical workflow for both procedures. The mean age was 60.3 ± 15 years. The diagnostic yield was positive in 98.5% (n = 69). Sixty-three biopsies (90%) were supratentorial and seven (10%) were infratentorial. Gliomas represented 54.3% of the patients (n = 38). There were two postoperative deaths (2.8%). No permanent morbidity related to surgery were observed. We did not find intraoperative technical problems with the device. There was no need to reposition the needle after the initial placement. Stereotactic robotic guided placement of laser ablation catheters and biopsy needles is safe, accurate, and can be implemented into a neurosurgical workflow.

Robot-Assisted Image-Guided Interventions

Image guidance is a common methodology of minimally invasive procedures. Depending on the type of intervention, various imaging modalities are available. Common imaging modalities are computed tomography, magnetic resonance tomography, and ultrasound. Robotic systems have been developed to enable and improve the procedures using these imaging techniques. Spatial and technological constraints limit the development of versatile robotic systems. This paper offers a brief overview of the developments of robotic systems for image-guided interventions since 2015 and includes samples of our current research in this field.

Robot-assisted stereoelectroencephalography electrode placement in twenty-three pediatric patients: a high-resolution analysis of individual lead placement time and accuracy at a single institution

PURPOSE

We describe a detailed evaluation of predictors associated with individual lead placement efficiency and accuracy for 261 stereoelectroencephalography (sEEG) electrodes placed for epilepsy monitoring in twenty-three children at our institution.

METHODS

Intra- and post-operative data was used to generate a linear mixed model to investigate predictors associated with three outcomes (lead placement time, lead entry error, lead target error) while accounting for correlated observations from the same patients. Lead placement time was measured using electronic time-stamp records stored by the ROSA software for each individual electrode; entry and target site accuracy was measured using postoperative stereotactic CT images fused with preoperative electrode trajectory planning images on the ROSA computer software. Predictors were selected from a list of variables that included patient demographics, laterality of leads, anatomic location of lead, skull thickness, bolt cap device used, and lead sequence number.

RESULTS

Twenty-three patients (11 female, 48%) of mean age 11.7 (± 6.1) years underwent placement of intracranial sEEG electrodes (median 11 electrodes) at our institution over a period of 1 year. There were no associated infections, hemorrhages, or other adverse events, and successful seizure capture was obtained in all monitored patients. The mean placement time for individual electrodes across all patients was 6.56 (± 3.5) min; mean target accuracy was 4.5 (± 3.5) mm. Lesional electrodes were associated with 25.7% (95% CI: 6.7-40.9%, p = 0.02) smaller target point errors. Larger skull thickness was associated with larger error: for every 1-mm increase in skull thickness, there was a 4.3% (95% CI: 1.2-7.5%, p = 0.007) increase in target error. Bilateral lead placement was associated with 26.0% (95% CI: 9.9-44.5%, p = 0.002) longer lead placement time. The relationship between placement time and lead sequence number was nonlinear: it decreased consistently for the first 4 electrodes, and became less pronounced thereafter.

CONCLUSIONS

Variation in sEEG electrode placement efficiency and accuracy can be explained by phenomena both within and outside of operator control. It is important to keep in mind the factors that can lead to better or worse lead placement efficiency and/or accuracy in order to maximize patient safety while maintaining the standard of care.

THE SAFETY AND EFFICACY OF ROBOT-ASSISTED STEREOTACTIC BIOPSY FOR BRAIN GLIOMA: EARLIEST INSTITUTIONAL EXPERIENCES AND EVALUATION OF LITERATURE

Robot-assisted brain tumor biopsy is becoming one of the most important innovative technologies in neurosurgical practice. The idea behind its engagement is to advance the safety and efficacy of the biopsy procedure, which is much in demand when planning the management of endocranial tumor pathology. Herein, we provide our earliest institutional experiences in utilizing this mesmerizing technology. Cranial robotic device was employed for stereotactic robot-assisted brain glioma biopsy in three consecutive patients from our series: an anaplastic isocitrate dehydrogenase (IDH) negative astrocytoma (WHO grade III) located in the right trigone region of the periventricular white matter; a low grade diffuse astrocytoma (WHO grade II) of bilateral thalamic region spreading into the right mesencephalic area; and an IDH-wildtype glioblastoma (WHO grade IV) of the right frontal lobe producing a contralateral midline shifting. Robot-assisted tumor biopsy was successfully performed to get tissue samples for histopathologic and immunohistochemical analysis. The adjacent tissue iatrogenic damage of the eloquent cortical areas was minimal, while the immediate postoperative recovery was satisfactory in all patients. In conclusion, considering the preliminary results of our early experiences, robot-assisted tumor biopsy was proven to be a feasible and accurate procedure when surgery for brain glioma was not an option. It may increase safety and precision, without expanding surgical time, being similarly effective when compared to standard stereotactic and manual biopsy. Using this method to provide accurate sampling for histopathologic and immunohistochemical analysis is a safe and easy way to determine management strategies and outcome of different types of brain glioma.

A Unique Case of Bilateral Thalamic High-Grade Glioma in a Pediatric Patient with LI-Fraumeni Syndrome: Case Presentation and Review of the Literature

Li-Fraumeni syndrome (LFS) is a rare high-penetrance and autosomal-dominant pathological condition caused by the germline mutation of the TP53 gene, predisposing to the development of tumors from pediatric age. We conducted a qualitative systematic review following the ENTREQ (Enhancing Transparency in Reporting the Synthesis of Qualitative Research) framework. A search was made in MEDLINE/Pubmed and MeSH Database using the terms "Li-Fraumeni" AND "pediatric high-grade glioma (HGG)", identifying six cases of HGGs in pediatric patients with LFS. We added a further case with peculiar features such as no familiar history of LFS, association of embryonal rhabdomyosarcoma and bithalamic HGG, whose immunohistochemical profile was accurately defined by Next Generation Sequencing. Knowledge synthesis and case analysis grounded the discussion about challenges in the management of this pathology in pediatric age.

Robot-assisted stereotactic biopsy of pediatric brainstem and thalamic lesions

OBJECTIVE

Biopsies of tumors located in deep midline structures require highly accurate stereotaxy to safely obtain lesional tissue suitable for molecular and histological analysis. Versatile platforms are needed to meet a broad range of technical requirements and surgeon preferences. The authors present their institutional experience with the robotic stereotactic assistance (ROSA) system in a series of robot-assisted biopsies of pediatric brainstem and thalamic tumors.

METHODS

A retrospective analysis was performed of 22 consecutive patients who underwent 23 stereotactic biopsies of brainstem or thalamic lesions using the ROSA platform at Rady Children's Hospital in San Diego between December 2015 and January 2020.

RESULTS

The ROSA platform enabled rapid acquisition of lesional tissue across various combinations of approaches, registration techniques, and positioning. No permanent deficits, major adverse outcomes, or deaths were encountered. One patient experienced temporary cranial neuropathy, and 3 developed small asymptomatic hematomas. The diagnostic success rate of the ROSA system was 91.3%.

CONCLUSIONS

Robot-assisted stereotactic biopsy of these lesions may be safely performed using the ROSA platform. This experience comprises the largest clinical series to date dedicated to robot-assisted biopsies of brainstem and diencephalic tumors.

Progress in diffuse intrinsic pontine glioma: advocating for stereotactic biopsy in the standard of care

Diffuse intrinsic pontine glioma (DIPG) is a universally fatal pediatric brainstem tumor affecting approximately 300 children in the US annually. Median survival is less than 1 year, and radiation therapy has been the mainstay of treatment for decades. Recent advances in the biological understanding of the disease have identified the H3K27M mutation in nearly 80% of DIPGs, leading to the 2016 WHO classification of diffuse midline glioma H3K27M-mutant, a grade IV brainstem tumor. Developments in epigenetic targeting of transcriptional tendencies have yielded potential molecular targets for clinical trials. Chimeric antigen receptor T cell therapy has also shown preclinical promise. Recent clinical studies, including prospective trials, have demonstrated the safety and feasibility of pediatric brainstem biopsy in the setting of DIPG and other brainstem tumors. Given developments in the ability to analyze DIPG tumor tissue to deepen biological understanding of this disease and develop new therapies for treatment, together with the increased safety of stereotactic brainstem biopsy, the authors present a case for offering biopsy to all children with suspected DIPG. They also present their standard operative techniques for image-guided, frameless stereotactic biopsy.

Frameless Stereotactic Biopsy with DTI-Based Tractography Integration: How to Adjust the Trajectory-A Case Series

BACKGROUND

Frameless stereotactic biopsy represents a minimally invasive procedure used for the histopathological diagnosis of brain tumors or to safely approach deep-seated lesions near eloquent areas not amenable for classical neurosurgical procedures. Traditionally, biopsy is performed relying on anatomical landmarks, but it can lead itself to intra- and postoperative complications, such as hemorrhage and fiber disruption. Diffusion tensor imaging (DTI) tractography represents a useful tool that can analyze the individual fiber tract conformation in cases of brain tumor and consequently identify the best biopsy trajectory, preserving white matter pathways. In our study, we present a novel technique that is based on the use of preoperative DTI for biopsy.

METHODS

Between January 2018 and January 2020, data about patients who underwent frameless biopsy using DTI tractography were retrospectively reviewed. The inclusion criterion was adult patients eligible for elective surgery for a single or multiple deep-seated lesions with contraindications to complete surgical resection.

RESULTS

We included 12 patients (mean age of 67.9 [±9.6] years). A single cranial lesion was detected in 7 cases, and multiple lesions in 5 cases. The use of DTI enabled the identification of white matter pathways in all cases and adjustment of the biopsy trajectory based on anatomical landmarks in 7 cases. Postoperative hematoma was reported in 1 case, and histological diagnosis was obtained in 11 cases.

CONCLUSION

According to our results, tractography is a useful tool that can enhance the safety of cerebral lesions biopsy sparing any fiber tract damages.

Robotic Stereotactic Assistance (ROSA) for Pediatric Epilepsy: A Single-Center Experience of 23 Consecutive Cases

Robotic assisted neurosurgery has become increasingly utilized for its high degree of precision and minimally invasive approach. Robotic stereotactic assistance (ROSA^®) for neurosurgery has been infrequently reported in the pediatric population. The goal of this case series was to describe the clinical experience, anesthetic and operative management, and treatment outcomes for pediatric patients with intractable epilepsy undergoing ROSA^® neurosurgery at a single-center institution. Patients who underwent implantation of stereoelectroencephalography (SEEG) leads for intractable epilepsy with ROSA^® were retrospectively evaluated between August 2016 and June 2018. Demographics, perioperative management details, complications, and preliminary seizure outcomes after resective or ablative surgery were reviewed. Nineteen children who underwent 23 ROSA^® procedures for SEEG implantation were included in the study. Mean operative time was 148 min. Eleven patients had subsequent resective or ablative surgery, and ROSA^® was used to assist with laser probe insertion in five patients for seizure foci ablation. In total, 148 SEEG electrodes were placed without any perioperative complications. ROSA^® is minimally invasive, provides superior accuracy for electrode placement, and requires less time than traditional surgical approaches for brain mapping. This emerging technology may improve the perioperative outcomes for pediatric patients with intractable epilepsy since large craniotomies are avoided; however, long-term follow-up studies are needed.

Robotic Surgical Assistant (ROSA™) Rehearsal: Using 3-Dimensional Printing Technology to Facilitate the Introduction of Stereotactic Robotic Neurosurgical Equipment

BACKGROUND

The use of frameless stereotactic robotic technology has rapidly expanded since the Food and Drug Administration's approval of the Robotic Surgical Assistant (ROSA™) in 2012. Although the safety and accuracy of the ROSA platform has been well-established, the introduction of complex robotic technology into an existing surgical practice poses technical and logistical challenges particular to a given institution.

OBJECTIVES

To better facilitate the integration of new surgical equipment into the armamentarium of a thriving pediatric neurosurgery practice by describing the use of a three-dimensional (3D)-printed patient model with in situ 3D-printed tumor for presurgical positioning and trajectory optimization in the stereotactic biopsy of a pontine lesion in a pediatric patient.

METHODS

A 3D model was created with an added silicone mock tumor at the anatomical position of the lesion. In a preoperative rehearsal session, the patient model was pinned and registered using the ROSA platform, and a mock biopsy was performed targeting the in Situ silicone tumor.

RESULTS

Utilization of the 3D-printed model enabled workflow optimization and increased staff familiarity with the logistics of the robotic technology. Biopsy trajectory successfully reached intralesional tissue on the 3D-printed model. The rehearsal maneuvers decreased operative and intubation time for the patient and improved operative staff familiarity with the robotic setup.

CONCLUSION

Use of a 3D-printed patient model enhanced presurgical positioning and trajectory planning in the biopsy of a difficult to reach pontine lesion in a pediatric patient. The ROSA rehearsal decreased operative time and increased staff familiarity with a new complex surgical equipment.

Robotic Surgical Assistant Rehearsal: Combining 3-Dimensional-Printing Technology With Preoperative Stereotactic Planning for Placement of Stereoencephalography Electrodes

BACKGROUND

The use of frameless stereotactic robotic technology has rapidly expanded since the Food and Drug Administration's approval of the Robotic Surgical Assistant (ROSA) in 2012. Although the use of the ROSA robot has greatly augmented stereotactic placement of intracerebral stereoelectroencephalography (sEEG) for the purposes of epileptogenic focus identification, the preoperative planning stages remain limited to computer software.

OBJECTIVE

To describe the use of a 3-dimensionally (3D)-printed patient model in the preoperative planning of ROSA-assisted depth electrode placement for epilepsy monitoring in a pediatric patient.

METHODS

An anatomically accurate 3D model was created and registered in a preoperative rehearsal session using the ROSA platform. After standard software-based electrode trajectory planning, sEEG electrodes were sequentially placed in the 3D model.

RESULTS

Utilization of the 3D-printed model enabled workflow optimization and increased staff familiarity with the logistics of the robotic technology as it relates to depth electrode placement. The rehearsal maneuvers enabled optimization of patient head positioning as well as identification of physical conflicts between 2 electrodes. This permitted revision of trajectory planning in anticipation of the actual case, thereby improving patient safety and decreasing operative time.

CONCLUSION

Use of a 3D-printed patient model enhanced presurgical positioning and trajectory planning in the placement of stereotactic sEEG electrodes for epilepsy monitoring in a pediatric patient. The ROSA rehearsal decreased operative time and increased efficiency of electrode placement.

Structural design of a positioning spherical parallel manipulator to be utilized in brain biopsy

BACKGROUND

During the last decades, there has been a great increase in the usage of robotic systems during surgeries in order to reach increased operational precision, reduced operation times, enhanced recovery periods, low infection risks, and limited scar formations for aesthetic reasons. In light of this, the current study focuses on the field of robotic surgery by introducing the kinematic structure of the precise robotic positioning manipulator for brain biopsy.

METHODOLOGY

Throughout the study, two degrees of freedom spherical parallel robot manipulator was proposed in order to position brain biopsy needle precisely during the brain biopsy operation on the target workspace.

RESULTS

Direct and inverse kinematics of the manipulator were carried out parametrically by using quaternion algebra. The prototype of the manipulator was manufactured by rapid prototyping for hardware verification.

CONCLUSIONS

Hardware verification of the manufactured prototype was completed distinctly by using motion capture cameras and manufactured mock-up setup that mimics tumour locations inside the brain. Successful verification results in terms of precision were achieved.

Direct Involvement of Cranial Nerve V at Diagnosis in Patients With Diffuse Intrinsic Pontine Glioma: A Potential Magnetic Resonance Predictor of Short-Term Survival

Background: Diffuse intrinsic pontine glioma (DIPG) has a dismal prognosis. Magnetic resonance imaging (MRI) remains the gold standard for non-invasive DIPG diagnosis. MRI features have been tested as surrogate biomarkers. We investigated the direct involvement of cranial nerve V (CN V) in DIPG at diagnosis and its utility as predictor of poor overall survival. Materials and Methods: We examined MRI scans of 35 consecutive patients with radiological diagnosis of DIPG. Direct involvement of CN V was assessed on the diagnostic scans. Differences in overall survival (OS) and time to progression (TTP) were analyzed for involvement of CN V, sex, age, tumor size, ring enhancement, and treatment regimen. Correlations between involvement of CN V and disease dissemination, magnet strength and slice thickness were analyzed. Statistical analyses included Kaplan-Meier curves, log-rank test and Spearman's Rho. Results: After excluding six long-term survivors, 29 patients were examined (15 M, 14 F). Four patients presented direct involvement of CN V. Histological data were available in 12 patients. Median OS was 11 months (range 3-23 months). Significant differences in OS were found for direct involvement of CN V (median OS: 7 months, 95% CI 1.1-12.9 months for involvement of CN V vs. 13 months, 95% CI 10.2-15.7 for lack of involvement of CN V, respectively, p < 0.049). Significant differences in TTP were found for the two treatment regimens (median TTP: 4 months, 95% CI 2.6-5.3 vs. 7 months, 95% CI 5.9-8.1, respectively, p < 0.027). No significant correlation was found between involvement of CN V and magnet strength or slice thickness (r = -0.201; p = NS). A trend toward positive correlation was found between direct involvement of CN V at diagnosis and dissemination of disease at follow-up (r = 0.347; p < 0.065). Conclusions: In our cohort, direct involvement of CN V correlated with poor prognosis. Based on our data, we suggest that in DIPG direct involvement of CN V should be routinely evaluated on diagnostic scans.

Safety and efficacy of Endoscopic Third Ventriculostomy in Diffuse Intrinsic Pontine Glioma related hydrocephalus: a Systematic Review

OBJECT

Diffuse Intrinsic Pontine Gliomas (DIPG) related hydrocephalus occurs as the result of tumor growth and Aqueduct obstruction. There is no consensus about the best surgical option, thus a review has been performed to clarify the rate of success, complications and possible issues of Endoscopic Third Ventriculostomy (ETV) in comparison to the other available techniques.

METHODS

This systematic review followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement and it was registered with the PROSPERO International Prospective Register of Systematic Reviews(CRD42018089001). MEDLINE, Web of Knowledge and EMBASE were searched for published series in which ETV was performed to treat hydrocephalus in DIPG patients.

RESULTS

Six studies were included. Two further cases coming from our experience were added, for a total amount of 55 patients treated through either ETV, VPS or Ventriculocisternal shunt according to Torkildsen. 86% of patients who underwent ETV experienced clinical improvement after surgery (p-value 0.03). Torkildsen shunt placement was associated to 50% failure rate. Two patients implanted with VPS developed symptoms of shunt malfunction and increased ventricular sizes (10%). Fisher's exact test was applied to compare efficacy of VPS and ETV with no statistical difference between the two group (p-value 0,17). Patients who underwent ETV did not experienced major complications and no procedural abortion was observed.

CONCLUSIONS

ETV is an effective and safe treatment option, associated to a low complications rate and a high success rate. Evidences from this review suggest to consider ETV as the first line treatment of hydrocephalus in DIPG patients.

Robot-assisted stereotactic brainstem biopsy in children: prospective cohort study

Tumours located within the brainstem comprise approximately a tenth of all paediatric brain tumours. Surgical biopsy of these tumours is technically challenging and has historically been associated with considerable risk. To this end, robot-assisted surgery theoretically allows for increased accuracy and precision. In this study we report our experience using the Neuromate robot (Renishaw, Gloucestershire, UK) to perform robot-assisted stereotactic biopsy in children with tumours located within the brainstem. An uncontrolled prospective cohort study was performed (phase II) according to the IDEAL model for safe surgical innovation. All cases were recorded on a prospectively maintained database. The database was searched over a 2-year period between the 1st December 2015 and the 31st November 2017 to identify all children with brainstem tumours that underwent robot-assisted stereotactic brain biopsy. When accessible, the post-operative MRI scans and pre-operative plans were compared to assess the target point localisation error (TPLE). Adverse events were recorded prospectively according to whether they resulted in increased hospital stay, caused neurological injury, or lead to death. In all, 11 consecutive children were identified with brain tumours located within the brainstem. In 10/11 cases specimens were diagnostic; in the remaining case a further biopsy was successful. The most frequent pathology was DIPG (7/15). Seven patients underwent an early post-operative volumetric MRI; the calculated median TPLE was 2.7 mm (range 0.5-4.2 mm). There were no surgical complications noted. Robot-assisted stereotactic biopsy in children appears to be feasible and safe. Research databases and comparative studies are warranted to further assess the technique.

Cutting Edge Therapeutic Insights Derived from Molecular Biology of Pediatric High-Grade Glioma and Diffuse Intrinsic Pontine Glioma (DIPG)

Pediatric high-grade glioma (pHGG) and brainstem gliomas are some of the most challenging cancers to treat in children, with no effective therapies and 5-year survival at ~2% for diffuse intrinsic pontine glioma (DIPG) patients. The standard of care for pHGG as a whole remains surgery and radiation combined with chemotherapy, while radiation alone is standard treatment for DIPG. Unfortunately, these therapies lack specificity for malignant glioma cells and have few to no reliable biomarkers of efficacy. Recent discoveries have revealed that epigenetic disruption by highly conserved mutations in DNA-packaging histone proteins in pHGG, especially DIPG, contribute to the aggressive nature of these cancers. In this review we pose unanswered questions and address unexplored mechanisms in pre-clinical models and clinical trial data from pHGG patients. Particular focus will be paid towards therapeutics targeting chromatin modifiers and other epigenetic vulnerabilities that can be exploited for pHGG therapy. Further delineation of rational therapeutic combinations has strong potential to drive development of safe and efficacious treatments for pHGG patients.

Clinically Relevant and Minimally Invasive Tumor Surveillance of Pediatric Diffuse Midline Gliomas Using Patient-Derived Liquid Biopsy

PURPOSE

Pediatric diffuse midline glioma (DMG) are highly malignant tumors with poor clinical outcomes. Over 70% of patients with DMG harbor the histone 3 p.K27M (H3K27M) mutation, which correlates with a poorer clinical outcome, and is also used as a criterion for enrollment in clinical trials. Because complete surgical resection of DMG is not an option, biopsy at presentation is feasible, but rebiopsy at time of progression is rare. While imaging and clinical-based disease monitoring is the standard of care, molecular-based longitudinal characterization of these tumors is almost nonexistent. To overcome these hurdles, we examined whether liquid biopsy allows measurement of disease response to precision therapy.

EXPERIMENTAL DESIGN

We established a sensitive and specific methodology that detects major driver mutations associated with pediatric DMGs using droplet digital PCR (n = 48 subjects, n = 110 specimens). Quantification of circulating tumor DNA (ctDNA) for H3K27M was used for longitudinal assessment of disease response compared with centrally reviewed MRI data.

RESULTS

H3K27M was identified in cerebrospinal fluid (CSF) and plasma in 88% of patients with DMG, with CSF being the most enriched for ctDNA. We demonstrated the feasibility of multiplexing for detection of H3K27M, and additional driver mutations in patient's tumor and matched CSF, maximizing the utility of a single source of liquid biome. A significant decrease in H3K27M plasma ctDNA agreed with MRI assessment of tumor response to radiotherapy in 83% (10/12) of patients.

CONCLUSIONS

Our liquid biopsy approach provides a molecularly based tool for tumor characterization, and is the first to indicate clinical utility of ctDNA for longitudinal surveillance of DMGs.

Robot-assisted stereotactic brain biopsy: systematic review and bibliometric analysis

INTRODUCTION

Stereotactic brain biopsy represents one of the earliest applications of surgical robotics. The aim of the present systematic review and bibliometric analysis was to evaluate the literature supporting robot-assisted brain biopsy and the extent to which the scientific community has accepted the technique.

METHODS

The Cochrane and PubMed databases were searched over a 30-year period between 1st of January 1988 and 31st of December 2017. Titles and abstracts were screened to identify publications that met the following criteria: (1) featured patients with brain pathology, (2) undergoing stereotactic brain biopsy, (3) reporting robot-assisted surgery, and (4) outcome data were provided. The reference lists of selected studies were also sought, and expert opinion sought to identify further eligible publications. Selected manuscripts were then reviewed, and data extracted on effectiveness and safety. The status of scientific community acceptance was determined using a progressive scholarly acceptance analysis.

RESULTS

All identified studies were non-randomised, including 1 retrospective cohort study and 14 case series or reports. The diagnostic biopsy rate varied from 75 to 100%, and the average target accuracy varied from 0.9 to 4.5 mm. Use of the robot was aborted in two operations owing to geometric inaccessibility and an error in image registration but no associated adverse events were reported. A compounding progressive scholarly acceptance analysis suggested a trend towards acceptance of the technique by the scientific community.

CONCLUSIONS

In conclusion, robot-assisted stereotactic brain biopsy is an increasingly mainstream tool in the neurosurgical armamentarium. Further evaluation should proceed along the IDEAL framework with research databases and comparative trials.

Potential New Therapies for Pediatric Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine glioma (DIPG) is an extensively invasive malignancy with infiltration into other regions of the brainstem. Although large numbers of specific targeted therapies have been tested, no significant progress has been made in treating these high-grade gliomas. Therefore, the identification of new therapeutic approaches is of great importance for the development of more effective treatments. This article reviews the conventional therapies and new potential therapeutic approaches for DIPG, including epigenetic therapy, immunotherapy, and the combination of stem cells with nanoparticle delivery systems.