Basic surgical techniques in the resection of malignant gliomas

Shaping the brain vasculature in development and disease in the single-cell era

The CNS critically relies on the formation and proper function of its vasculature during development, adult homeostasis and disease. Angiogenesis - the formation of new blood vessels - is highly active during brain development, enters almost complete quiescence in the healthy adult brain and is reactivated in vascular-dependent brain pathologies such as brain vascular malformations and brain tumours. Despite major advances in the understanding of the cellular and molecular mechanisms driving angiogenesis in peripheral tissues, developmental signalling pathways orchestrating angiogenic processes in the healthy and the diseased CNS remain incompletely understood. Molecular signalling pathways of the 'neurovascular link' defining common mechanisms of nerve and vessel wiring have emerged as crucial regulators of peripheral vascular growth, but their relevance for angiogenesis in brain development and disease remains largely unexplored. Here we review the current knowledge of general and CNS-specific mechanisms of angiogenesis during brain development and in brain vascular malformations and brain tumours, including how key molecular signalling pathways are reactivated in vascular-dependent diseases. We also discuss how these topics can be studied in the single-cell multi-omics era.

Perilesional resection technique of glioblastoma: intraoperative ultrasound and histological findings of the resection borders in a single center experience

INTRODUCTION

The surgical goal in glioblastoma treatment is the maximal safe resection of the tumor. Currently the lack of consensus on surgical technique opens different approaches. This study describes the "perilesional technique" and its outcomes in terms of the extent of resection, progression free survival and overall survival.

METHODS

Patients included (n = 40) received a diagnosis of glioblastoma and underwent surgery using the perilesional dissection technique at "San Gerardo Hospital"between 2018 and 2021. The tumor core was progressively isolated using a circumferential movement, healthy brain margins were protected with Cottonoid patties in a "shingles on the roof" fashion, then the tumorwas removed en bloc. Intraoperative ultrasound (iOUS) was used and at least 1 bioptic sample of "healthy" margin of the resection was collected and analyzed. The extent of resection was quantified. Extent of surgical resection (EOR) and progression free survival (PFS)were safety endpoints of the procedure.

RESULTS

Thirty-four patients (85%) received a gross total resection(GTR) while 3 (7.5%) patients received a sub-total resection (STR), and 3 (7.5%) a partial resection (PR). The mean post-operative residual volume was 1.44 cm³ (range 0-15.9 cm³).During surgery, a total of 76 margins were collected: 51 (67.1%) were tumor free, 25 (32.9%) were infiltrated. The median PFS was 13.4 months, 15.3 in the GTR group and 9.6 months in the STR-PR group.

CONCLUSIONS

Perilesional resection is an efficient technique which aims to bring the surgeon to a safe environment, carefully reaching the "healthy" brain before removing the tumoren bloc. This technique can achieve excellent tumor margins, extent of resection, and preservation of apatient's functions.

Microsurgical subpial resections for diffuse gliomas-old wine in a new bottle

BACKGROUND

Maximizing resection is an oft-sought-after albeit challenging goal in diffuse gliomas. Microsurgical technique remains the mainstay.

METHOD

By virtue of their pattern of growth and spread, gliomas respect anatomical boundaries like the pia. Using subpial dissection, en bloc resections provide the most optimal surgical technique. This paper revisits this technique and describes the rationale and basic principles integrating it in the modern multimodal glioma surgery workflow.

CONCLUSION

Subpial resection is a very useful and "anatomical" technique for en bloc resection of diffuse gliomas which is easy to master and execute and optimizes the extent of resection and minimizes complications effectively.

Minimally invasive keyhole temporal lobectomy approach for supramaximal glioma resection: A safety and feasibility study

With a recent trend towards supra-maximal resection for gliomas and minimally invasive techniques, keyhole temporal lobectomies may serve an important role in neurosurgical oncology. Due to their location and proximity to eloquent brain, temporal lobe gliomas offer unique challenges that may limit the extent of resection. Here we describe a modified technique using mini-craniotomies through a keyhole approach for temporal lobectomies in glioma patients. We retrospectively reviewed data from consecutive patients who underwent temporal lobectomies for resection of gliomas from 2012 to 2018. Demographic data, extent of tumor resection, pre and post-op KPS, short term and long term complications, as well as other relevant data were collected. We identified 57 patients who underwent keyhole-mini craniotomy for temporal lobectomies for glioma. Surgical procedures were performed in 12 patients for low-grade glioma (LGG) and 45 patients for high-grade glioma (HGG). Awake craniotomies were performed in 15 of the cases, and 13 cases were for tumor recurrence. Supra-maximal resection (SMR) was achieved in 15 patients, while gross total resection (GTR) and near total resection (NTR) achieved in 32 patients and 10 patients, respectively. Average pre- and post-op KPS were equivalent, and post-operative complications requiring surgical intervention were experienced in 4 patients. Here we show that our modified keyhole craniotomy is both safe and effective in achieving SMR or GTR in glioma patients, with minimal morbidity. This minimally-invasive temporal lobectomy may be an instrumental tool for neurosurgical oncologists transitioning to less invasive techniques.

Predictive measures and outcomes of extent of resection in juvenile pilocytic astrocytoma

PURPOSE

The present study aims to determine the tumor-related, clinical, and demographic factors associated with extent of resection (EOR) and post-operative outcomes in JPA patients.

METHODS

All patients with JPA, identified from a single-center brain tumour data base, were included in this retrospective analysis. Pre-operative MRI scans were reviewed by a single neurosurgeon blinded to the EOR. JPA cases that exhibited no residual tumor post-operatively were assigned to the GTR group, all other tumors were assigned to the <GTR group. Tumor-related, clinical and demographic variables as well as perioperative morbidities were compared between both groups.

RESULTS

Of the 28 patients included, 15 had a GTR (46% male; median age: 7.5 years; range: 1.16-14.9) and 13 had <GTR (69.2% male; median age: 10.6 years; range: 0.66-17.68). Tumor location reached statistical significance, as there were significantly more cerebellar tumors in the GTR group (86.7%) compared to the <GTR group (38.5%) (p = 0.016). GTR cases had a significantly longer average follow-up interval (6.6 months) than <GTR cases (4.5 months) (p = 0.031). All demographic variables, clinical variables and tumor-related factors showed no significant differences between the two groups. There were no differences between GTR and <GTR cases in terms of perioperative outcomes.

CONCLUSIONS

This study shows other than location of the lesion in the cerebellum, demographic, clinical and tumor-related variables are not associated with EOR in children with JPA. GTR was associated with an extended follow-up interval but not with increased perioperative morbidities compared to those with <GTR.

Perilesional Resection of Glioblastoma Is Independently Associated With Improved Outcomes

BACKGROUND

Resection is a critical component in the initial treatment of glioblastoma (GBM). Often GBMs are resected using an intralesional method. Circumferential perilesional resection of GBMs has been described, but with limited data.

OBJECTIVE

To conduct an observational retrospective analysis to test whether perilesional resection produced a greater extent of resection.

METHODS

We identified all patients with newly diagnosed GBM who underwent resection at our institution from June 1, 1993 to December 31, 2015. Demographics, presenting symptoms, intraoperative data, method of resection (perilesional or intralesional), volumetric imaging data, and postoperative outcomes were obtained. Complete resection (CR) was defined as 100% resection of all contrast-enhancing disease. Univariate analyses employed analysis of variance (ANOVA) and Fisher's exact test. Multivariate analyses used propensity score-weighted multivariate logistic regression.

RESULTS

Newly diagnosed GBMs were resected in 1204 patients, 436 tumors (36%) perilesionally and 766 (64%) intralesionally. Radiographic CR was achieved in 69% of cases. Multivariate analysis demonstrated that perilesional tumor resection was associated with a significantly higher rate of CR than intralesional resection (81% vs 62%, multivariate odds ratio = 2.5, 95% confidence interval: 1.8-3.4, P < .001). Among tumors in eloquent cortex, multivariate analysis showed that patients who underwent perilesional resection had a higher rate of CR (79% vs 58%, respectively, P < .001) and a lower rate of neurological complications (11% vs 20%, respectively, P = .018) than those who underwent intralesional resection.

CONCLUSION

Circumferential perilesional resection of GBM is associated with significantly higher rates of CR and lower rates of neurological complications than intralesional resection, even for tumors arising in eloquent locations. Perilesional resection, when feasible, should be considered as a preferred option.

The Survival Advantage of "Supratotal" Resection of Glioblastoma Using Selective Cortical Mapping and the Subpial Technique

BACKGROUND

A substantial body of evidence suggests that cytoreductive surgery is a prerequisite to prolonging survival in patients with glioblastoma (GBM).

OBJECTIVE

To evaluate the safety and impact of "supratotal" resections beyond the zone of enhancement seen on magnetic resonance imaging scans, using a subpial technique.

METHODS

We retrospectively evaluated 86 consecutive patients with primary GBM, managed by the senior author, using a subpial resection technique with or without carmustine (BCNU) wafer implantation. Multivariate Cox proportional hazards regression was used to analyze clinical, radiological, and outcome variables. Overall impacts of extent of resection (EOR) and BCNU wafer placement were compared using Kaplan-Meier survival analysis.

RESULTS

Mean patient age was 56 years. The median OS for the group was 18.1 months. Median OS for patients undergoing gross total, near-total, and subtotal resection were 54, 16.5, and 13.2 months, respectively. Patients undergoing near-total resection ( P = .05) or gross total resection ( P < .01) experienced statistically significant longer survival time than patients undergoing subtotal resection as well as patients undergoing ≥95% EOR ( P < .01) when compared to <95% EOR. The addition of BCNU wafers had no survival advantage.

CONCLUSIONS

The subpial technique extends the resection beyond the contrast enhancement and is associated with an overall survival beyond that seen in similar series where resection of the enhancement portion is performed. The effect of supratotal resection on survival exceeded the effects of age, Karnofsky performance score, and tumor volume. A prospective study would help to quantify the impact of the subpial technique on quality of life and survival as compared to a traditional resection limited to the enhancing tumor.

Outcome of fully awake craniotomy for lesions near the eloquent cortex: analysis of a prospective surgical series of 79 supratentorial primary brain tumors with long follow-up

BACKGROUND

Despite possible advantages, few surgical series report specifically on awake craniotomy for intrinsic brain tumors in eloquent brain areas.

OBJECTIVES

Primary: To evaluate the safety and efficacy of fully awake craniotomy (FAC) for the resection of primary supratentorial brain tumors (PSBT) near or in eloquent brain areas (EBA) in a developing country. Secondary: To evaluate the impact of previous surgical history and different treatment modalities on outcome.

PATIENTS AND METHODS

From 1998 to 2007, 79 consecutive FACs for resection PSBT near or in EBA, performed by a single surgeon, were prospectively followed. Two groups were defined based on time period and surgical team: group A operated on from March 1998 to July 2004 without a multidisciplinary team and group B operated on from August 2004 to October 2007 in a multidisciplinary setting. For both time periods, two groups were defined: group I had no previous history of craniotomy, while group II had undergone a previous craniotomy for a PSBT. Forty-six patients were operated on in group A, 46 in group B, 49 in group I and 30 in group II. Psychological assessment and selection were obligatory. The preferred anesthetic procedure was an intravenous high-dose opioid infusion (Fentanil 50 microg, bolus infusion until a minimum dose of 10 microg/kg). Generous scalp and periosteous infiltrations were performed. Functional cortical mapping was performed in every case. Continuous somato-sensory evoked potentials (SSEPs) and phase reversal localization were available in 48 cases. Standard microsurgical techniques were performed and monitored by continuous clinical evaluation.

RESULTS

Clinical data showed differences in time since clinical onset (p < 0.001), slowness of thought (p = 0.02) and memory deficits (p < 0.001) between study periods and also time since recent seizure onset for groups I and II (p = 0.001). Mean tumor volume was 51.2 +/- 48.7 cm3 and was not different among the four groups. The mean extent of tumor reduction was 90.0 +/- 12.7% and was similar for the whole series. A trend toward a larger incidence of glioblastoma multiforme occurred in group B (p = 0.05) and I (p = 0.04). Recovery of previous motor deficits was observed in 75.0% of patients, while motor worsening in 8.9% of cases. Recovery of semantic language deficits, control of refractory seizures and motor worsening were statistically more frequent in group B (p = 0.01). Satisfaction with the procedure was reported by 89.9% of patients, which was similar for all groups. Clinical complications were minimal, and surgical mortality was 1.3%.

CONCLUSIONS

These data suggest that FAC is safe and effective for the resection of PSBT in EBA as the main technique, and in a multidisciplinary context is associated with greater clinical and physiological monitoring. The previous history of craniotomy for PSBT did not seem to influence the outcome.

Awake craniotomy for brain tumors near eloquent cortex: correlation of intraoperative cortical mapping with neurological outcomes in 309 consecutive patients

OBJECTIVE

Intraoperative localization of cortical areas for motor and language function has been advocated to minimize postoperative neurological deficits. We report herein the results of a retrospective study of cortical mapping and subsequent clinical outcomes in a large series of patients.

METHODS

Patients with intracerebral tumors near and/or within eloquent cortices (n = 309) were clinically evaluated before surgery, immediately after, and 1 month and 3 months after surgery. Craniotomy was tailored to encompass tumor plus adjacent areas presumed to contain eloquent cortex. Intraoperative cortical stimulation for language, motor, and/or sensory function was performed in all patients to safely maximize surgical resection.

RESULTS

A gross total resection (> or =95%) was obtained in 64%, and a resection of 85% or more was obtained in 77% of the procedures. Eloquent areas were identified in 65% of cases, and in that group, worsened neurological deficits were observed in 21% of patients, whereas only 9% with negative mapping sustained such deficits (P < 0.01). Intraoperative neurological deficits occurred in 64 patients (21%); of these, 25 (39%) experienced worsened neurological outcome at 1 month, whereas only 27 of 245 patients (11%) without intraoperative changes had such outcomes (P < 0.001). At 1 month, 83% overall showed improved or stable neurological status, whereas 17% had new or worse deficits; however, at 3 months, 7% of patients had a persistent neurological deficit. Extent of resection less than 95% also predicted worsening of neurological status (P < 0.025).

CONCLUSION

Negative mapping of eloquent areas provides a safe margin for surgical resection with a low incidence of neurological deficits. However, identification of eloquent areas not only failed to eliminate but rather increased the risk of postoperative deficits, likely indicating close proximity of functional cortex to tumor.

Safety profile of carmustine wafers in malignant glioma: a review of controlled trials and a decade of clinical experience

BACKGROUND

Carmustine (1,3-bis [2-chloroethyl]-1-nitrosourea, or BCNU) wafers are approved for recurrent glioblastoma and newly diagnosed malignant glioma (MG). Based on considerable clinical experience and use in multimodal regimens, the safety of BCNU wafers needs a re-evaluation.

SCOPE

A review of literature from 1996 to February 2008 was conducted on the safety of BCNU wafer in MG patients using search criteria in Medline, EMBASE, and BIOSIS. Abstracts from relevant US and European meetings were also evaluated. Three Phase III (two were pivotal) and 26 non-Phase III studies met inclusion criteria. Overall incidence was estimated for each adverse event (AE), and data from individual studies were summarised as median (range) rates. Comparisons were based on consistent similarities or differences across overall incidence, median rate and range.

FINDINGS

BCNU wafer group AE rates from the two pivotal Phase III trials ranged from 4-23% for cerebral oedema, 4-9% for intracranial hypertension, 14-16% for healing abnormalities, 5% for CSF leaks, 4-5% for intracranial infection, 19-33% for seizures, 10% for deep vein thrombosis, and 8% for pulmonary embolus. There were no notable differences in AE rates between the two pivotal Phase III and 26 non-Phase III studies. For the non-pivotal studies, the overall incidence of AEs was low, ranging from 0.2% for intracranial hypertension to 9.6% for healing abnormalities. Healing abnormalities, intracranial infection, and seizures were the most consistently reported AEs, having been observed in 16, 12, and 11 studies, respectively. Rates of healing abnormalities appeared higher in recurrent than in newly diagnosed disease. There were no notable differences between BCNU wafer plus adjuvant treatment (e.g., temozolomide) and BCNU wafer alone, with the exception of haematologic toxicity.

CONCLUSION

This review of safety data for BCNU wafers provides reassurance that the AE rates reported in current treatment strategies including multimodal treatment approaches are comparable to those observed in the initial registration studies. The broad range of AE rates may reflect differences in the perioperative and postoperative management. Clinical experience suggests that strategies may exist to reduce the risk of complications.

Intracranial Tumours. Neurosurgeons View

The role of imaging in the treatment of brain tumours viewed from the neurosurgeons perspective is described. The importance of evaluating various aspects of intracranial tumours for the prognosis, selection of treatment and execution of the operation is reviewed. The impact of imaging on operation planning, intraoperative use of neuronavigation, MRI CT and USG on the outcome of treatment is presented. Close cooperation between neuroradiologist and neurosurgeon guarantees better outcomes for the patients and further improvements in brain tumour treatment.

The postoperative brain tumour stem cell (BTSC) niche and cancer recurrence

Currently, surgical resection is one of only a few options for treating brain cancer. Unfortunately, postoperative tumour recurrence remains almost inevitable despite additional radiation or chemotherapy treatment following resection. Clinical observations and a growing body of experimental evidence have led to speculation that there is a population of persistent brain tumour stem cells (BTSCs)--or brain tumour initiating cells--that are difficult to completely remove surgically. Furthermore, residual BTSCs following surgery may actually be more resistant to subsequent radiation and/or chemotherapies. It remains to be determined if brain surgeries render the postoperative tissue microenvironment more favourable for the survival and growth of BTSCs, and therefore the recurrence of brain tumours.We hypothesise that BTSC-based tumour recurrence may develop within a specific niche of the aberrant tumour microenvironment. Even when the gross appearance of the primary tumour seems confined, BTSCs (albeit accounting only for a small population of tumour cells) may microscopically enter the stroma, hampering curative surgeries. This article discusses the theory that surgical resection of brain tumours generates niches recruiting BTSCs to the surgical wounds, stimulating the proliferation and invasiveness of BTSCs, and leading to tumour recurrence. Postoperative brains are marked with active wound repair in peritumoural margins, which is likely to be accompanied by increased inflammatory paracrine production, angiogenesis and reactive astrogliosis. The postoperative BTSC niche concept is consistent with the observation that brain tumour recurrence usually occurs in tissues that are proximal to the resection margin. In this article, we intend to reflect recent advances that may lead to novel strategies to eliminate postoperative brain tumour recurrence.

Liquid-crystal tunable filter spectral imaging for brain tumor demarcation

Past studies have demonstrated that combined fluorescence and diffuse reflectance spectroscopy can successfully discriminate between normal, tumor core, and tumor margin tissues in the brain. To achieve efficient, real-time surgical resection guidance with optical biopsy, probe-based spectroscopy must be extended to spectral imaging to spatially demarcate the tumor margins. We describe the design and characterization of a combined fluorescence and diffuse reflectance imaging system that uses liquid-crystal tunable filter technology. Experiments were conducted to quantitatively determine the linearity, field of view, spatial and spectral resolution, and wavelength sensitivity of the imaging system. Spectral images were acquired from tissue phantoms, mouse brain in vitro, and human cortex in vivo for functional testing of the system. The spectral imaging system produces measured intensities that are linear with sample emission intensity and integration time and possesses a 1 in. (2.54 cm) field of view for a 7 in. (18 cm) object distance. The spectral resolution is linear with wavelength, and the spatial resolution is pixel-limited. The sensitivity spectra for the imaging system provide a guide for the distribution of total image integration time between wavelengths. Functional tests in vitro demonstrate the capability to spectrally discriminate between brain tissues based on exogenous fluorescence contrast or endogenous tissue composition. In vivo imaging captures adequate fluorescence and diffuse reflectance intensities within a clinically viable 2 min imaging time frame and demonstrates the importance of hemostasis to acquired signal strengths and imaging speed.

Comparison of spectral variation from spectroscopy to spectral imaging

Optical biopsy has been shown to discriminate between normal and diseased tissue with high sensitivity and specificity. Fiber-optic probe-based spectroscopy systems do not provide the necessary spatial information to guide therapy effectively, ultimately requiring a transition from probe-based spectroscopy to spectral imaging. The effect of such a transition on fluorescence and diffuse reflectance line shape is investigated. Inherent differences in spectral line shape between spectroscopy and imaging are characterized and many of these differences may be attributed to a shift in illumination-collection geometry between the two systems. Sensitivity of the line-shape disparity is characterized with respect to changes in sample absorption and scattering as well as to changes in various parameters of the fiber-optic probe design (e.g., fiber diameter, beam steering). Differences in spectral line shape are described in terms of the relative relationship between the light diffusion within the tissue and the distribution of source-detector separation distances for the probe-based and imaging illumination-collection geometries. Monte Carlo simulation is used to determine fiber configurations that minimize the line-shape disparity between the two systems. In conclusion, we predict that fiber-optic probe designs that mimic a spectral imaging geometry and spectral imaging systems designed to emulate a probe-based geometry will be difficult to implement, pointing toward a posteriori correction for illumination-collection geometry to reconcile imaging and probe-based spectral line shapes or independent evaluation of tissue discrimination accuracy for probe-based and spectral imaging systems.

Glioblastoma multiforme in the elderly: a therapeutic challenge

INTRODUCTION

Elderly patients with glioblastoma multiforme (GBM) are frequently excluded from cancer therapy trials, treated suboptimally or not treated at all. The average survival in elderly patients is 4-8 months. The goal of the present study was to evaluate the efficacy of different treatment options in terms of survival in an elderly population affected with GBM.

MATERIALS AND METHODS

About 34 Patients with primary supratentorial GBM aged 65 or higher were included in this study. All patients underwent craniotomy and tumor mass resection. After surgery they received radiation therapy, chemotherapy and radioimmunotherapy in different combinations.

RESULTS

Overall median survival was 10.5 months with one patient still alive at 35 months. Survival was longer for patients who underwent total resection instead of partial (13 months vs 4 months, P=0.006). If total en-bloc resection was used a further survival advantage was obtained (16 months for en-bloc resection, 9 months for inside-out resection, P=0.008). Where a second surgical intervention was performed median survival was 21 months (P=0.05). Survival according to adjuvant therapy has been 21 months (radiotherapy, chemotherapy, radioimmunotheraphy), 18 months (radiotherapy, chemotherapy) and 7 months (radiotherapy) (P=0.0001).

CONCLUSIONS

We think that single prognostic factor such as age should be not a reason for undertreatment.

Diffusely infiltrative low-grade gliomas in adults

Diffusely infiltrating low-grade gliomas (LGGs) include astrocytomas, oligodendrogliomas, and mixed oligoastrocytomas (WHO grade 2). Due to the routine use of magnetic resonance imaging, there is an increasing need to formulate treatment guidelines for patients with LGGs. However, there is little consensus about the optimal treatment strategy for diffusely infiltrative LGGs, and the clinical management of LGGs is one of the most controversial areas in neurooncology. Although the standard of care has not been established, several randomized trials are beginning to provide some answers. Furthermore, laboratory correlative studies are defining subsets of LGG that may identify patients with better prognoses and increased chance of responding to therapy. This article reviews the most recent data regarding the treatment of LGG, emphasizing evidenced based approaches from current clinical trials.

Dynamic, three-dimensional optical tracking of an ablative laser beam

Surgical resection remains the treatment of choice for brain tumors with infiltrating margins but is currently limited by visual discrimination between normal and neoplastic marginal tissues during surgery. Imaging modalities such as computed tomography, magnetic resonance, positron emission tomography, and optical techniques can accurately localize tumor margins. We believe coupling the fine resolution of current imaging techniques with the precise cutting of midinfrared lasers through image-guided neurosurgery can greatly enhance tumor margin resection. This paper describes a feasibility study designed to optically track in three-dimensional space the articulated arm delivery of a noncontact ablative laser beam. To enable optical tracking of the laser beam focus, infrared-emitting diodes (IREDs) were attached to a handpiece machined for the distal end of the articulated arm of a surgical carbon dioxide laser. Crosstalk between the ablative laser beam and the tracking diodes was measured. The geometry of the adapted laser handpiece was characterized to track an externally attached passive tip and the laser beam focus. Target localization accuracies were assessed for both instrument points-of-interest and the sources of tracking errors were investigated. Stray infrared laser light did not affect optical tracking accuracy. The mean target registration errors while optically tracking the laser handpiece with a passive tip and the laser beam focus were 1.31+/-0.50 mm and 2.31+/-0.92 mm, respectively, and were equivalent to the errors tracking a 24-IRED pen probe from Northern Digital in a side-by-side comparison. The majority of error during ablation tracking derived from registration accuracy between physical space and the defined space of the ablation phantom and from an inability to freehand align the laser focus with the target in a consistent manner. While their magnitudes depend on spatial details of the tracking setup (e.g., number and distribution of fiducial points, working distance from the camera, etc.), these errors are inherent to any freehand laser surgery.

Cost of migration: invasion of malignant gliomas and implications for treatment

Tumors of glial origin consist of a core mass and a penumbra of invasive, single cells, decreasing in numbers towards the periphery and still detectable several centimeters away from the core lesion. Several decades ago, the diffuse nature of malignant gliomas was recognized by neurosurgeons when super-radical resections using hemispherectomies failed to eradicate these tumors. Local invasiveness eventually leads to regrowth of a recurrent tumor predominantly adjacent to the resection cavity, which is not significantly altered by radiation or chemotherapy. This raises the question of whether invasive glioma cells activate cellular programs that render these cells resistant to conventional treatments. Clinical and experimental data demonstrate that glioma invasion is determined by several independent mechanisms that facilitate the spread of these tumors along different anatomic and molecular structures. A common denominator of this cellular behavior may be cell motility. Gene-expression profiling showed upregulation of genes related to motility, and functional studies demonstrated that cell motility contributes to the invasive phenotype of malignant gliomas. There is accumulating evidence that invasive glioma cells show a decreased proliferation rate and a relative resistance to apoptosis, which may contribute to chemotherapy and radiation resistance. Interestingly, interference with cell motility by different strategies results in increased susceptibility to apoptosis, indicating that this dynamic relationship can potentially be exploited as an anti-invasive treatment paradigm. In this review, we discuss mechanisms of glioma invasion, characteristics of the invasive cell, and consequences of this cellular phenotype for surgical resection, oncologic treatments, and future perspectives for anti-invasive strategies.

Optimizing outcomes with maximal surgical resection of malignant gliomas

BACKGROUND

Aggressive surgical resection of malignant gliomas is a controversial issue in neurosurgery. Studies with rigorous methodology that fully address this issue have only recently become available.

METHODS

The controversy regarding the role of maximal surgical resection of malignant gliomas is reviewed. The authors discuss surgical techniques and adjunctive technologies that can be utilized to assist in resection of these lesions.

RESULTS

Using current microneurosurgical techniques, it is possible to resect malignant gliomas in gross total fashion. An aggressive approach in which 98% or more of the tumor mass is resected results in a statistically significant survival advantage.

CONCLUSIONS

An aggressive surgical procedure for malignant gliomas can result in increased survival duration for selected groups of patients.

Current surgical management of glioblastoma

Surgical resection is a critical aspect of the management of a patient with a glioblastoma (GBM). An intimate knowledge of the anatomy of a GBM, as well as familiarity with particular surgical techniques and adjunctive technologies is required for safe surgical resection. The goals of resection include diagnosis, relief of mass effect, and cytoreduction. A recent study showed that resection of 98% or more of the tumor mass can result in a statistically significant survival advantage. Even in functionally critical areas, "gross total" resections are possible if proper techniques are employed. It is recommended that a "gross total" resection of the enhancing portion of a GBM be performed whenever possible. With this philosophy, the mortality rate is 3% and the rate of major neurologic morbidity is less than 10%.

In vivo brain tumor demarcation using optical spectroscopy

The applicability of optical spectroscopy for intraoperative detection of brain tumors/tumor margins was investigated in a pilot clinical trial consisting of 26 brain tumor patients. The results of this clinical trial suggest that brain tumors and infiltrating tumor margins (ITM) can be effectively separated from normal brain tissues in vivo using combined autofluorescence and diffuse-reflectance spectroscopy. A two-step empirical discrimination algorithm based on autofluorescence and diffuse reflectance at 460 and 625 nm was developed. This algorithm yields a sensitivity and specificity of 100 and 76%, respectively, in differentiating ITM from normal brain tissues. Blood contamination was found to be a major obstacle that attenuates the accuracy of brain tumor demarcation using optical spectroscopy. Overall, this study indicates that optical spectroscopy has the potential to guide brain tumor resection intraoperatively with high sensitivity.