Low-grade oligodendroglioma: an indolent but incurable disease? Clinical article

Malignant Progression of Diffuse Low-grade Gliomas: A Systematic Review and Meta-analysis on Incidence and Related Factors

Malignant progression of diffuse low-grade glioma (LGG) is a critical event affecting patient survival; however, the incidence and related factors have been inconsistent in literature. According to the PRISMA guidelines, we systematically reviewed articles from 2009, meta-analyzed the incidence of malignant progression, and clarified factors related to the transformation. Forty-one articles were included in this study (n = 7,122; n, number of patients). We identified two definitions of malignant progression: histologically proven (Htrans) and clinically defined (Ctrans). The malignant progression rate curves of Htrans and Ctrans were almost in parallel when constructed from the results of meta-regression by the mean follow-up time. The true transformation rate was supposed to lie between the two curves, approximately 40% at the 10-year mean follow-up. Risk of malignant progression was evaluated using hazard ratio (HR). Pooled HRs were significantly higher in tumors with a larger pre- and postoperative tumor volume, lower degree of resection, and notable preoperative contrast enhancement on magnetic resonance imaging than in others. Oligodendroglial histology and IDH mutation (IDHm) with 1p/19q codeletion (Codel) also significantly reduced the HRs. Using Kaplan-Meier curves from eight studies with molecular data, we extracted data and calculated the 10-year malignant progression-free survival (10yMPFS). The 10yMPFS in patients with IDHm without Codel was 30.4% (95% confidence interval [95% CI]: 22.2-39.0) in Htrans and 38.3% (95% CI: 32.3-44.3) in Ctrans, and that with IDHm with Codel was 71.7% (95% CI: 61.7-79.5) in Htrans and 62.5% (95% CI: 55.9-68.5) in Ctrans. The effect of adjuvant radiotherapy or chemotherapy could not be determined.

The Effect of Radiotherapy on Diffuse Low-Grade Gliomas Evolution: Confronting Theory with Clinical Data

Diffuse low-grade gliomas are slowly growing tumors that always recur after treatment. In this paper, we revisit the modeling of the evolution of the tumor radius before and after the radiotherapy process and propose a novel model that is simple yet biologically motivated and that remedies some shortcomings of previously proposed ones. We confront this with clinical data consisting of time series of tumor radii from 43 patient records by using a stochastic optimization technique and obtain very good fits in all cases. Since our model describes the evolution of a tumor from the very first glioma cell, it gives access to the possible age of the tumor. Using the technique of profile likelihood to extract all of the information from the data, we build confidence intervals for the tumor birth age and confirm the fact that low-grade gliomas seem to appear in the late teenage years. Moreover, an approximate analytical expression of the temporal evolution of the tumor radius allows us to explain the correlations observed in the data.

Towards in-vivo label-free detection of brain tumor margins with epi-illumination tomographic quantitative phase imaging

Brain tumor surgery involves a delicate balance between maximizing the extent of tumor resection while minimizing damage to healthy brain tissue that is vital for neurological function. However, differentiating between tumor, particularly infiltrative disease, and healthy brain in-vivo remains a significant clinical challenge. Here we demonstrate that quantitative oblique back illumination microscopy (qOBM)-a novel label-free optical imaging technique that achieves tomographic quantitative phase imaging in thick scattering samples-clearly differentiates between healthy brain tissue and tumor, including infiltrative disease. Data from a bulk and infiltrative brain tumor animal model show that qOBM enables quantitative phase imaging of thick fresh brain tissues with remarkable cellular and subcellular detail that closely resembles histopathology using hematoxylin and eosin (H&E) stained fixed tissue sections, the gold standard for cancer detection. Quantitative biophysical features are also extracted from qOBM which yield robust surrogate biomarkers of disease that enable (1) automated tumor and margin detection with high sensitivity and specificity and (2) facile visualization of tumor regions. Finally, we develop a low-cost, flexible, fiber-based handheld qOBM device which brings this technology one step closer to in-vivo clinical use. This work has significant implications for guiding neurosurgery by paving the way for a tool that delivers real-time, label-free, in-vivo brain tumor margin detection.

Extent of resection and survival for oligodendroglioma: a U.S. population-based study

BACKGROUND

National guidelines recommend maximal safe resection of low-grade and high-grade oligodendrogliomas. However, there is no level 1 evidence to support these guidelines, and recent retrospective studies on the topic have yielded mixed results.

OBJECTIVE

To assess the association between extent of resection (EOR) and survival for oligodendrogliomas in the general U.S.

POPULATION

METHODS

Cases diagnosed between 2004 and 2013 were selected from the Surveillance, Epidemiology, and End-Results (SEER) Program and retrospectively analyzed for treatment, prognostic factors, and survival times. Cases that did not undergo tumor de-bulking surgery (e.g. no surgery or biopsy alone) were compared to subtotal resection (resection) and gross-total resection (GTR). The primary end-points were overall survival (OS) and cause-specific survival (CSS). An external validation cohort with 1p/19q-codeleted tumors was creating using the TCGA and GSE16011 datasets.

RESULTS

3135 Cases were included in the final analysis. The 75% survival time (75ST) and 5-year survival rates were 47 months and 70.8%, respectively. Subtotal resection (STR, 75ST = 50 months) and GTR (75ST = 61 months) were associated with improved survival times compared to cases that did not undergo surgical debulking (75ST = 20 months, P < 0.001 for both), with reduced hazard ratios (HRs) after controlling for other factors (HR 0.81 [0.68-0.97] and HR 0.65 [0.54-0.79], respectively). GTR was associated with improved OS in both low-grade and anaplastic oligodendroglioma subgroups (HR 0.74 [0.58-0.95], HR 0.60 [0.44-0.82], respectively) while STR fell short of significance in the subgroup analysis. All findings were corroborated by multivariable analysis of CSS and externally validated in a cohort of patients with 1p19q-codeleted tumors.

CONCLUSION

Greater EOR is associated with improved survival in oligodendrogliomas. Our findings in this U.S. population-based cohort support national guidelines.

Seizures at presentation are correlated with better survival outcomes in adult diffuse glioma: A systematic review and meta-analysis

PURPOSE

Seizures are the most common presenting sign of patients with diffuse glioma. In the current study, we performed a meta-analysis to determine the correlation of seizures at presentation to survival outcomes in adult diffuse glioma, and the possible mechanisms were also discussed.

METHODS

A comprehensive literature search was performed in PUBMED, EMBASE, Web of Science and the Cochrane Central Register of Controlled Trials. The pooled hazard ratio (HR) and corresponding 95% confidence interval (CI) were used to estimate effects. Heterogeneity among studies and publication bias were also evaluated.

RESULTS

11 studies with 2088 patients were finally included for the current meta-analysis. Seizure-free preoperatively was significantly associated with a poor overall survival in patients with diffuse glioma, the pooled HR was 1.73 (95% CI 1.43-2.08, Z = 5.71, p < 0.001). Subgroup analysis was also performed by tumor grade, the same association was identified in both low-grade glioma (pooled HR 2.49, 95% CI 1.47-4.20, Z = 3.40, p < 0.001) and glioblastoma (pooled HR 1.46, 95% CI 1.27-1.68, Z = 5.24, p < 0.001). A significant correlation of seizure-free with a poor progression-free survival was also identified (pooled HR 1.42, 95% CI 1.06-1.92, Z = 2.33, p = 0.02), although only 3 studies comprising 368 patients were included.

CONCLUSION

The current study determined that seizures at presentation were an independent predictor of better survival outcomes in adult diffuse glioma. It is the first study which provides a comprehensive standardized assessment of the association between seizures at presentation with long-term survival outcomes in patients with diffuse glioma.

Oligodendroglioma resection: a Surveillance, Epidemiology, and End Results (SEER) analysis

OBJECTIVE

The available evidence suggests that the clinical benefits of extended resection are limited for chemosensitive tumors, such as primary CNS lymphoma. Oligodendroglioma is generally believed to be more sensitive to chemotherapy than astrocytoma of comparable grades. In this study the authors compare the survival benefit of gross-total resection (GTR) in patients with oligodendroglioma relative to patients with astrocytoma.

METHODS

Using the Surveillance, Epidemiology, and End Results (SEER) Program (1999–2010) database, the authors identified 2378 patients with WHO Grade II oligodendroglioma (O2 group) and 1028 patients with WHO Grade III oligodendroglioma (O3 group). Resection was defined as GTR, subtotal resection, biopsy only, or no resection. Kaplan-Meier and multivariate Cox regression survival analyses were used to assess survival with respect to extent of resection.

RESULTS

Cox multivariate analysis revealed that the hazard of dying from O2 and O3 was comparable between patients who underwent biopsy only and GTR (O2: hazard ratio [HR] 1.06, 95% confidence interval [CI] 0.73–1.53; O3: HR 1.18, 95% CI 0.80–1.72). A comprehensive search of the published literature identified 8 articles without compelling evidence that GTR is associated with improved overall survival in patients with oligodendroglioma.

CONCLUSIONS

This SEER-based analysis and review of the literature suggest that GTR is not associated with improved survival in patients with oligodendroglioma. This finding contrasts with the documented association between GTR and overall survival in anaplastic astrocytoma and glioblastoma. The authors suggest that this difference may reflect the sensitivity of oligodendroglioma to chemotherapy as compared with astrocytomas.

Prognostic markers for survival in patients with oligodendroglial tumors; a single-institution review of 214 cases

Background

In the 2016 WHO classification, the diagnosis of oligodendroglioma has been restricted to IDH mutated, 1p19q codeleted tumors (IDHmut-codel). IDHmut oligoastrocytoma is now classified either as oligodendroglioma or astrocytoma based on presence of 1p19q codeletion. There is growing evidence that this molecular classification more closely reflects patient outcome. Due to the strong association between IDHmut-codel with oligodendroglial morphology, the additional impact of these markers on prognostic accuracy is largely unknown. Our aim was to assess the prognostic impact of IDHmut-codel in an unselected cohort of morphologically classified oligodendroglial tumors.

Methods

We performed a retrospective chart review of oligodendroglial tumors (WHO grade II and III) operated since 1983. A total of 214 tumors were included, and molecular information was available for 96 tumors. The prognostic impact of IDHmut-codel together with clinical parameters was analyzed by multivariate Cox regression.

Results

IDHmut-codel was registered in 64 tumors while for 150 tumors the molecular profile was negative for IDHmut-codel, unknown or incomplete. Comparison between the two groups showed that patients with IDHmut-codel tumors were younger (42 vs. 48 years), had more frequent frontal tumor location (48 vs. 33%) and presented more often with seizures (72 vs. 51%) and no signs of neurological impairment (14 vs. 30%) than patients harboring tumors with unknown or incomplete molecular profile. Multivariate survival analysis identified young age (HR 1.78 ≥ 40 years), the absence of neurological deficits or personality changes (HR 0.57), frontal tumor location (HR 0.64) and the presence of IDHmut-codel (HR 0.50) as independent predictors for longer survival, whereas tumor grade was not.

Conclusion

In this unselected single-institution cohort, the presence of IDHmut-codel was associated with more beneficial clinical parameters and was identified as an independent prognostic factor. We conclude that the classical oligodendroglioma genotype provides additional prognostic data beyond clinical characteristics, morphology and tumor grade.

The role of radiotherapy in the management of patients with diffuse low grade glioma: A systematic review and evidence-based clinical practice guideline

QUESTIONS

(1) What is the optimal role of external beam radiotherapy in the management of adult patients with newly diagnosed low-grade glioma (LGG) in terms of improving outcome (i.e., survival, complications, seizure control or other reported outcomes of interest)? (2) Which radiation strategies (dose, timing, fractionation, stereotactic radiation, brachytherapy, chemotherapy) improve outcomes compared to standard external beam radiation therapy in the initial management of low grade gliomas in adults? (3) Do specific factors (e.g., age, volume, extent of resection, genetic subtype) identify subgroups with better outcomes following radiation therapy than the general population of adults with newly diagnosed low-grade gliomas?

TARGET POPULATION

These recommendations apply to adults with newly diagnosed diffuse LGG.

RECOMMENDATIONS

OUTCOMES IN ADULT PATIENTS WITH NEWLY DIAGNOSED LOW GRADE GLIOMA TREATED WITH RADIOTHERAPY: Level I Radiotherapy is recommended in the management of newly diagnosed low-grade glioma in adults to prolong progression free survival, irrespective of extent of resection. Level II Radiotherapy is recommended in the management of newly diagnosed low grade glioma in adults as an equivalent alternative to observation in preserving cognitive function, irrespective of extent of resection. Level III Radiotherapy is recommended in the management of newly diagnosed low grade glioma in adults to improve seizure control in patients with epilepsy and subtotal resection. Level III Radiotherapy is recommended in the management of newly diagnosed low-grade glioma in adults to prolong overall survival in patients with subtotal resection. Level III Consideration of the risk of radiation induced morbidity, including cognitive decline, imaging abnormalities, metabolic dysfunction and malignant transformation, is recommended when the delivery of radiotherapy is selected in the management of newly diagnosed low-grade glioma in adults. STRATEGIES OF RADIOTHERAPY IN ADULT PATIENTS WITH NEWLY DIAGNOSED LOW GRADE GLIOMA: Level I Lower dose radiotherapy is recommended as an equivalent alternative to higher dose immediate postoperative radiotherapy (45-50.4 vs. 59.4-64.8 Gy) in the management of newly diagnosed low-grade glioma in adults with reduced toxicity. Level III Delaying radiotherapy until recurrence or progression is recommended as an equivalent alternative to immediate postoperative radiotherapy in the management of newly diagnosed low-grade glioma in adults but may result in shorter time to progression. Level III The addition of chemotherapy to radiotherapy is not recommended over whole brain radiotherapy alone in the management of low-grade glioma, as it provides no additional survival benefit. Level III Limited-field radiotherapy is recommended over whole brain radiotherapy in the management of low-grade glioma. Level III Either stereotactic radiosurgery or brachytherapy are recommended as acceptable alternatives to external radiotherapy in selected patients. PROGNOSTIC FACTORS IN ADULT PATIENTS WITH NEWLY DIAGNOSED LOW GRADE GLIOMA TREATED WITH RADIOTHERAPY: Level II It is recommended that age greater than 40 years, astrocytic pathology, diameter greater than 6 cm, tumor crossing the midline and preoperative neurological deficit be considered as negative prognostic indicators when predicting overall survival in adult low grade glioma patients treated with radiotherapy. Level II It is recommended that smaller tumor size, extent of surgical resection and higher mini-mental status exam be considered as positive prognostic indicators when predicting overall survival and progression free survival in patients in adult low grade glioma patients treated with radiotherapy. Level III It is recommended that seizures at presentation, presence of oligodendroglial histological component and 1p19q deletion (along with additional relevant factors-see Table 1) be considered as positive prognostic indicators when predicting response to radiotherapy in adults with low grade gliomas. Level III It is recommended that increasing age, decreasing performance status, decreasing cognition, presence of astrocytic histological component (along with additional relevant factors (see Tables 1, 2) be considered as negative prognostic indicators when predicting response to radiotherapy.

The role of surgery in the management of patients with diffuse low grade glioma: A systematic review and evidence-based clinical practice guideline

QUESTION

Should patients with imaging suggestive of low grade glioma (LGG) undergo observation versus treatment involving a surgical procedure?

TARGET POPULATION

These recommendations apply to adults with imaging suggestive of a WHO grade 2 glioma (oligodendroglioma, astrocytoma, or oligo-astrocytoma).

RECOMMENDATIONS

Surgical resection is recommended over observation to improve overall survival for patients with diffuse low-grade glioma (Level III) although observation has no negative impact on cognitive performance and quality of life (Level II).

QUESTION

What is the impact of extent of resection on progression free survival (PFS) or overall survival (OS) in LGG patients?

TARGET POPULATION

These recommendations apply to adults with imaging suggestive of a WHO grade 2 glioma (oligodendroglioma, astrocytoma, or oligo-astrocytoma).

RECOMMENDATIONS

IMPACT OF EXTENT OF RESECTION ON PFS:

LEVEL II

It is recommended that GTR or STR be accomplished instead of biopsy alone when safe and feasible so as to decrease the frequency of tumor progression recognizing that the rate of progression after GTR is fairly high.

IMPACT OF EXTENT OF RESECTION ON OS

LEVEL III

Greater extent of resection can improve OS in LGG patients.

QUESTION

What tools are available to increase extent of resection in LGG patients?

TARGET POPULATION

These recommendations apply to adults with imaging suggestive of a WHO grade 2 glioma (oligodendroglioma, astrocytoma, or oligo-astrocytoma).

RECOMMENDATIONS

INTRAOPERATIVE MRI DURING SURGERY:

LEVEL III

The use of intraoperative MRI should be considered as a method of increasing the extent of resection of LGGs.

QUESTION

What is the impact of surgical resection on seizure control and accuracy of pathology in low grade glioma patients?

TARGET POPULATION

These recommendations apply to adults with imaging suggestive of a WHO grade 2 glioma (oligodendroglioma, astrocytoma, or oligo-astrocytoma).

RECOMMENDATIONS

SURGICAL RESECTION AND SEIZURE CONTROL:

LEVEL III

After taking into account the patient's clinical status and tumor location, gross total resection is recommended for patients with diffuse LGG as a way to achieve more favorable seizure control.

ACCURACY OF DIAGNOSIS

LEVEL III

Taking into account the patient's clinical status and tumor location, surgical resection should be carried out to maximize the chance of accurate diagnosis.

QUESTION

What tools can improve the safety of surgery for LGGs in eloquent locations?

TARGET POPULATION

These recommendations apply to adults with imaging suggestive of a WHO grade 2 glioma (oligodendroglioma, astrocytoma, or oligo-astrocytoma).

RECOMMENDATIONS

PREOPERATIVE IMAGING:

LEVEL III

It is recommended that preoperative functional MRI and diffusion tensor imaging be utilized in the appropriate clinical setting to improve functional outcome after surgery for LGG.

INTRAOPERATIVE MAPPING OF TUMORS IN ELOQUENT AREAS

LEVEL III

Intraoperative mapping is recommended for patients with diffuse LGGs in eloquent locations compared to patients with non-eloquently located diffuse LGGs as a way of preserving function.

Beyond the World Health Organization grading of infiltrating gliomas: advances in the molecular genetics of glioma classification

BACKGROUND

Traditional classification of diffuse infiltrating gliomas (DIGs) as World Health Organization (WHO) grades II-IV is based on histological features of a heterogeneous population of tumors with varying prognoses and treatments. Over the last decade, research efforts have resulted in a better understanding of the molecular basis of glioma formation as well as the genetic alterations commonly identified in diffuse gliomas.

METHODS

A systematic review of the current literature related to advances in molecular phenotypes, mutations, and genomic analysis of gliomas was carried out using a PubMed search for these key terms. Data was studied and synthesized to generate a comprehensive review of glioma subclassification.

RESULTS

This new data helps supplement the existing WHO grading scale by subtyping gliomas into specific molecular groups. The emerging molecular profile of diffuse gliomas includes the studies of gene expression and DNA methylation in different glioma subtypes. The discovery of novel mutations in isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) provides new biomarkers as points of stratification of gliomas based on prognosis and treatment response. Gliomas that harbor CpG island hypermethylator phenotypes constitute a subtype of glioma with improved survival. The difficulty of classifying oligodendroglial lineage of tumors can be aided with identification of 1p/19q codeletion. Glioblastomas (GBMs) previously described as primary or secondary can now be divided based on gene expression into proneural, mesenchymal, and classical subtypes and the identification of mutations in the promoter region of the telomerase reverse transcriptase (TERTp) have been correlated with poor prognosis in GBMs.

CONCLUSIONS

Incorporation of new molecular and genomic changes into the existing WHO grading of DIGs may provide better patient prognostication as well as advance the development of patient-specific treatments and clinical trials.

Comparing high-resolution microscopy techniques for potential intraoperative use in guiding low-grade glioma resections

BACKGROUND AND OBJECTIVES

Fluorescence image-guided surgery (FIGS), with contrast provided by 5-ALA-induced PpIX, has been shown to enable a higher extent of resection of high-grade gliomas. However, conventional FIGS with low-power microscopy lacks the sensitivity to aid in low-grade glioma (LGG) resection because PpIX signal is weak and sparse in such tissues. Intraoperative high-resolution microscopy of PpIX fluorescence has been proposed as a method to guide LGG resection, where sub-cellular resolution allows for the visualization of sparse and punctate mitochondrial PpIX production in tumor cells. Here, we assess the performance of three potentially portable high-resolution microscopy techniques that may be used for the intraoperative imaging of human LGG tissue samples with PpIX contrast: high-resolution fiber-optic microscopy (HRFM), high-resolution wide-field microscopy (WFM), and dual-axis confocal (DAC) microscopy.

MATERIALS AND METHODS

Thick unsectioned human LGG tissue samples (n = 7) with 5-ALA-induced PpIX contrast were imaged using three imaging techniques (HRFM, WFM, DAC). The average signal-to-background ratio (SBR) was then calculated for each imaging modality (5 images per tissue, per modality).

RESULTS

HRFM provides the ease of use and portability of a flexible fiber bundle, and is simple and inexpensive to build. However, in most cases (6/7), HRFM is not capable of detecting PpIX signal from LGGs due to high autofluorescence, generated by the fiber bundle under laser illumination at 405 nm, which overwhelms the PpIX signal and impedes its visualization. WFM is a camera-based method possessing high lateral resolution but poor axial resolution, resulting in sub-optimal image contrast.

CONCLUSIONS

Consistent successful detection of PpIX signal throughout our human LGG tissue samples (n = 7), with an acceptable image contrast (SBR >2), was only achieved using DAC microscopy, which offers superior image resolution and contrast that is comparable to histology, but requires a laser-scanning mechanism to achieve optical sectioning.

Adult low-grade glioma: 19-year experience at a single institution

OBJECTIVES

To determine prognostic factors and optimal timing of postoperative radiation therapy (RT) in adult low-grade gliomas.

METHODS

Records from 554 adults diagnosed with nonpilocytic low-grade gliomas at Mayo Clinic between 1992 and 2011 were retrospectively reviewed.

RESULTS

Median follow-up was 5.2 years. Histology revealed astrocytoma in 22%, oligoastrocytoma in 34%, and oligodendroglioma in 45%. Initial surgery achieved gross total resection in 31%, radical subtotal resection in 10%, subtotal resection (STR) in 21%, and biopsy only in 39%. Median overall survival (OS) and progression-free survival (PFS) were 11.4 and 4.1 years, respectively. On multivariate analysis, factors associated with lower OS included astrocytomas and use of postoperative RT. Adverse prognostic factors for PFS on multivariate analysis included tumor size, astrocytomas, STR/biopsy only and not receiving RT. Patients undergoing gross total resection/radical subtotal resection had the best OS and PFS. Comparing survival with the log-rank test demonstrated no association between RT and PFS (P=0.24), but RT was associated with lower OS (P<0.0001). In patients undergoing STR/biopsy only, RT was associated with improved PFS (P<0.0001) but lower OS (P=0.03). Postoperative RT was associated with adverse prognostic factors including age > 40 years, deep tumors, size≥5 cm, astrocytomas and STR/biopsy only. Patients delaying RT until recurrence experienced 10-year OS (71%) similar to patients never needing RT (74%; P=0.34).

CONCLUSIONS

This study supports the association between aggressive surgical resection and better OS and PFS, and between postoperative RT and improved PFS in patients receiving STR/biopsy only. In addition, our findings suggest that delaying RT until progression is safe in patients who are eligible.

Emerging operative strategies in neurosurgical oncology

PURPOSE OF REVIEW

In recent years, the safety and efficacy of neurosurgical intervention has rapidly improved for brain tumor patients. Technological advances, combined with refined intraoperative techniques, now enable well tolerated surgical access to any region of the human brain. For patients with gliomas, these improvements have redefined the clinical possibilities, and here we review several emerging operative strategies that are essential for next-generation neurosurgical oncologists and major brain tumor centers.

RECENT FINDINGS

The value of glioma extent of resection remains controversial, but review of the modern literature reveals important opportunities for early neurosurgical intervention. Although microsurgical resection must be balanced by the risk of neurological compromise, improvements in intraoperative stimulation techniques now enable resection of highly eloquent tumors with minimal morbidity. Additionally, the emergence of fluorescence-guided surgery as a new operative paradigm provides a unique opportunity to resect tumors to the margins of microscopic infiltration.

SUMMARY

Neurosurgical intervention remains the first step in effective glioma management. With intraoperative mapping techniques, aggressive microsurgical resection can be safely pursued even when tumors occupy essential functional pathways. With the development of tumor-specific fluorophores, such as 5-aminolevulinic acid, real-time microscopic visualization of tumor infiltration can be surgically targeted prior to adjuvant therapy.

LOH 19q indicates shorter disease progression-free interval in low-grade oligodendrogliomas with EMP3 methylation

We previously described a cohort of grade II oligodendroglioma (OII) patients, in whom the loss of heterozygosity (LOH) 19q was present in the subgroup at a higher risk of relapse. In this study, we evaluated the CpG methylation of the putative tumor suppressor epithelial membrane protein 3 (EMP3, 19q13.3) gene promoter in the same OII cohort, to investigate whether a correlation could be found between EMP3 cytogenetic and epigenetic loss and higher risk of relapse. Twenty-three tumor samples from OII patients were collected over a period of 10 years. Seventeen glioblastoma (GBM) samples (2 of which were relapses) were collected from 15 patients. The EMP3, O6-methylguanine methyltransferase (MGMT) and cyclooxygenase 2 (COX2) promoter methylation, evaluated by methylation-specific PCR, and the isocitrate dehydrogenase 1 (IDH1) mutation, identified by sequencing, were compared between the OII and GBM histotypes. The EMP3 promoter methylation was correlated with the analysis of LOH 19q, performed by microsatellite amplification, in OII patients. Disease progression-free interval was evaluated in the OII patients with the EMP3 methylation with either LOH 19q or conserved chromosome 19 arms. The EMP3 and MGMT promoter methylation was more frequent in OII than in GBM patients, and the IDH1 mutation was absent in GBM. The COX2 promoter was unmethylated in both histotypes. Both LOH+/- 19q OII patients showed EMP3 hypermethylation. Concomitant LOH 19q and EMP3 gene promoter methylation was observed in the OII patients at a higher risk of relapse. Our results suggest that a total (cytogenetic and epigenetic) functional loss of both EMP3 alleles accounts for the reduced disease progression-free interval in OII patients. Although the small sample size limits the strength of this study, our results support testing this hypothesis in larger cohorts of patients, considering the methylation of the EMP3 gene promoter together with LOH 19q as an indication for treatment with adjuvant therapy ab initio in order to improve the overall survival of OII patients.

Seizures and the natural history of World Health Organization Grade II gliomas: a review

OBJECTIVE

The majority of adults with low-grade gliomas have seizures. Despite the frequency of seizures as initial symptoms and symptoms of later disease, seizures in relation to the natural course of low-grade gliomas have received little attention.

METHODS

In this review, we provide an update of the literature on the prognostic impact of preoperative seizures and discuss the tumor- and treatment-related factors affecting seizure control at later stages of the disease.

RESULTS

Seizures occur most frequently at disease presentation and predict a more favorable outcome. Initial seizures are correlated with tumor location and possibly indirectly to the molecular profile of the tumor. About 50% of all patients with seizures at presentation continue to have seizures before surgery. Maximal tumor resection, including resection of epileptic foci, is a valuable strategy for improving seizure control. In addition, radiotherapy and chemotherapy, as single therapies or in combination with surgery, have shown beneficial effects in terms of seizure reduction. Recurrent seizures after macroscopically complete tumor resection may be a marker for accelerated tumor growth. Recurrent seizures after an initial transient stabilization after radiotherapy and/or chemotherapy may be a marker for anaplastic tumor transformation.

CONCLUSION

Preoperative seizures likely reflect, apart from tumor location, intrinsic tumor properties as well. Change in seizure control in individual patients is frequently associated with altered tumor behavior. Including seizures and seizure control as clinical parameters is recommended in future trials of low-grade gliomas to further establish the prognostic value of these symptoms and to identify the factors affecting seizure control.

Seizure characteristics and outcomes in 508 Chinese adult patients undergoing primary resection of low-grade gliomas: a clinicopathological study

Seizure is a common presenting manifestation and plays an important role in the clinical presentation and quality of life for patients with low-grade gliomas (LGGs). The authors set out to identify factors that influence preoperative seizure characteristics and postoperative seizure control. Cases involving adult patients who had undergone initial surgery for LGGs in a single institution between 2005 and 2009 were retrospectively reviewed. Univariate and multivariate logistic regression analyses were used to identify factors associated with preoperative seizures and postoperative seizure control. Of the 508 patients in the series, 350 (68.9%) presented with seizures. Age less than 38 years and cortical involvement of tumor were more likely to be associated with seizures (P = .003 and .001, respectively, multivariate logistic analysis). For the cohort of 350 patients with seizures, Engel classification was used to evaluate 6- and 12-month outcome after surgery: completely seizure free (Engel class I), 65.3% and 62.5%; not seizure free (Engel classes II, III, IV), 34.7% and 37.5%. After multivariate logistic analysis, favorable seizure prognosis was more common in patients with secondary generalized seizure (P = .006) and with calcification on MRI (.031). With respect to treatment-related variables, patients achieved much better seizure control after gross total resection than after subtotal resection (P < .0001). Ki67 was an independent molecular marker predicting poor seizure control in the patients with a history of seizure if overexpressed but was not a predictor for those without preoperative seizures. These factors may provide insight into developing effective treatment strategies aimed at prolonging patients' survival.

Intraoperative confocal microscopy in the visualization of 5-aminolevulinic acid fluorescence in low-grade gliomas

OBJECT

Greater extent of resection (EOR) for patients with low-grade glioma (LGG) corresponds with improved clinical outcome, yet remains a central challenge to the neurosurgical oncologist. Although 5-aminolevulinic acid (5-ALA)-induced tumor fluorescence is a strategy that can improve EOR in gliomas, only glioblastomas routinely fluoresce following 5-ALA administration. Intraoperative confocal microscopy adapts conventional confocal technology to a handheld probe that provides real-time fluorescent imaging at up to 1000× magnification. The authors report a combined approach in which intraoperative confocal microscopy is used to visualize 5-ALA tumor fluorescence in LGGs during the course of microsurgical resection.

METHODS

Following 5-ALA administration, patients with newly diagnosed LGG underwent microsurgical resection. Intraoperative confocal microscopy was conducted at the following points: 1) initial encounter with the tumor; 2) the midpoint of tumor resection; and 3) the presumed brain-tumor interface. Histopathological analysis of these sites correlated tumor infiltration with intraoperative cellular tumor fluorescence.

RESULTS

Ten consecutive patients with WHO Grades I and II gliomas underwent microsurgical resection with 5-ALA and intraoperative confocal microscopy. Macroscopic tumor fluorescence was not evident in any patient. However, in each case, intraoperative confocal microscopy identified tumor fluorescence at a cellular level, a finding that corresponded to tumor infiltration on matched histological analyses.

CONCLUSIONS

Intraoperative confocal microscopy can visualize cellular 5-ALA-induced tumor fluorescence within LGGs and at the brain-tumor interface. To assess the clinical value of 5-ALA for high-grade gliomas in conjunction with neuronavigation, and for LGGs in combination with intraoperative confocal microscopy and neuronavigation, a Phase IIIa randomized placebo-controlled trial (BALANCE) is underway at the authors' institution.

Prognosis of oligodendroglial tumor with ring enhancement showing central necrotic portion

Oligodendroglial tumors sometimes show heterogeneous ring enhancement with a central necrotic portion. We aimed to reveal the prognosis of such tumors based on such radiologic findings and compare them to other prognostic factors. Participants were 32 patients with oligodendroglioma (17 oligodendrogliomas, 15 anaplastic oligodendrogliomas) who underwent surgery from 2004 to 2008. We investigated tumor radiologic findings, locations, calcification, whether localized or diffuse type, and enhancement patterns. Of other prognostic factors, we analyzed age, sex, pathology, extent of removal, adjuvant therapy, genetic change in 1p and 19q, and MGMT methylation status. We checked for genetic abnormality in 1p and 19q using the FISH method. To investigate MGMT methylation, we performed methylation-specific PCR (MSP). Mean follow-up duration was 3.2 years. Median age was 42.4 years, and the male:female ratio was 21:11. Out of 17 oligodendrogliomas, 14 (82.4%) showed combined 1p/19q deletion, and 14 (82.4%), methylated MGMT. Among 15 anaplastic oligodendrogliomas, there were 7 (46.6%) with combined 1p/19q deletion and 11 (73.3%) with methylated MGMT. The 4-year recurrence-free survival and overall survival were 77.6 and 100% in oligodendrogliomas and 59.1 and 71.6% in anaplastic oligodendrogliomas, respectively. On univariate analysis, radiologic variable of ring enhancement pattern was statistically significant related with recurrence-free survival (P = 0.003). Variables such as sex (P = 0.03), combined 1p/19q loss (P = 0.04), tumor location (P = 0.02), and anaplastic pathology (P = 0.04) were significantly correlated with overall survival. Cox's regression model revealed that ring enhancement pattern was associated with frequent recurrence (ring enhancement, hazard ratio = 8.281, P = 0.04), and these showed 1p deletion only. Anaplastic oligodendrogliomas with ring enhancement like glioblastomas and without combined 1p/19q loss should receive close follow-up after treatment because of frequent recurrences.

Favorable long-term outcome of low-grade oligodendrogliomas irrespective of 1p/19q status when treated without radiotherapy

Despite the accumulating evidences of high chemosensitivity especially in anaplastic oligodendrogliomas with loss of chromosomes 1p and 19q, the optimal management strategy for low-grade tumors using the 1p/19q information remains controversial. We have treated all low-grade oligodendrogliomas by a chemotherapy-preceding strategy without radiotherapy, and here we analyzed the survival outcomes of 36 consecutive patients in relation to 1p/19q status. The treatment protocol was as follows: (1) simple observation after gross total resection, and (2) modified PCV chemotherapy for postoperative residual tumors or recurrence after total resection. The 1p and 19q status were analyzed by fluorescence in situ hybridization. The median follow-up period was 7.5 years and no patient was lost during the follow-up periods. 1p/19q co-deletion was observed in 72% of the patients, and there was no significant association between 1p/19q co-deletion and chemotherapy response rate. The 5- and 10-year progression-free survival (PFS) rate was 75.1 and 46.9%, respectively, and the median PFS was 121 months for 1p/19q-deleted tumors and 101 months for non-deleted tumors (log-rank test: P = 0.894). Extent of surgery did not affect PFS (P = 0.685). In contrast, the elder patients (>50) had significantly shorter PFS (P = 0.0458). Recurrent tumors were well controlled by chemotherapy irrespective of 1p/19q status, and 35 out of 36 patients survived without receiving radiotherapy. The 5- and 10-year overall survival rates were 100 and 93.8%, respectively. Two of the patients in their sixties (29%) suffered from severe cognitive dysfunctions and marked brain atrophy following chemotherapy alone. These results show that low-grade oligodendrogliomas could be successfully treated by surgical resection and nitrosourea-based chemotherapy alone without radiotherapy irrespective of 1p/19q status.