Oligodendroglioma: incidence and biological behavior in a defined population

Intratumoral calcification: not only a diagnostic but also a prognostic indicator in oligodendrogliomas

OBJECTIVE

Calcification is a hallmark characteristic of oligodendroglioma (ODG) that may be used as a diagnostic factor, but its prognostic implications remain unclear. This study aimed to investigate the features of calcified ODGs and to evaluate the differences in survival between patients with calcified and noncalcified ODGs.

METHODS

We retrospectively reviewed the records of 305 consecutive patients who were diagnosed with IDH-mutant, 1p/19q codeleted ODG at our institution from July 2009 to August 2020. Patients with intratumoral calcification were identified. The clinical, radiologic, and molecular features of the patients in the calcified group and noncalcified group were recorded. Univariate and multivariate analyses were performed to identify prognostic factors.

RESULTS

Of the 305 patients, 112 (36.7%) were confirmed to have intratumoral calcification. Compared to ODGs without calcification, ODGs with calcifications had a larger tumor diameter; lower degree of resection; higher tumor grade; higher MGMT methylation level; higher Ki-67 index; and higher rates of midline crossing, enhancement, cyst, and 1q/19p copolysomy, and patients with calcification were more likely to receive chemoradiotherapy. ODGs with T2 hypointense calcification had a higher Hounsfield unit (HU) value on CT scans, and a lower degree of resection. Patients with T2 hypointense calcification ODGs had a shorter survival than those with non-hypointense calcification ODGs. ODGs with calcification and cysts showed a higher Ki-67 index, tumor grade, and enhanced rate, and the patients had an unfavorable overall survival (OS). Calcification was found to be a negative prognostic factor for both progression-free survival (PFS) and OS by univariate analysis, which was confirmed by the Cox proportional hazard model.

CONCLUSIONS

Calcification is a useful negative prognostic factor for PFS and OS in patients with ODGs and could therefore be helpful in guiding personalized treatment and predicting patient prognosis.

CLINICAL RELEVANCE STATEMENT

Calcification can serve as an independent prognostic factor for patients with oligodendroglioma and shows a vital role in guiding individualized treatment.

KEY POINTS

• Intratumoral calcification is an independent negative prognostic risk factor for progression-free survival and overall survival in oligodendroglioma patients. • Calcifications in oligodendroglioma can be divided into hypointense and non-hypointense subtypes based on T2-weighted imaging, and patients with T2-hypointense calcification oligodendrogliomas have worse prognosis. • Calcification concurrent with cysts indicates a more aggressive phenotype of oligodendrogliomas and a significantly reduced survival rate.

In Vitro Effects of Methylprednisolone over Oligodendroglial Cells: Foresight to Future Cell Therapies

The implantation of oligodendrocyte precursor cells may be a useful therapeutic strategy for targeting remyelination. However, it is yet to be established how these cells behave after implantation and whether they retain the capacity to proliferate or differentiate into myelin-forming oligodendrocytes. One essential issue is the creation of administration protocols and determining which factors need to be well established. There is controversy around whether these cells may be implanted simultaneously with corticosteroid treatment, which is widely used in many clinical situations. This study assesses the influence of corticosteroids on the capacity for proliferation and differentiation and the survival of human oligodendroglioma cells. Our findings show that corticosteroids reduce the capacity of these cells to proliferate and to differentiate into oligodendrocytes and decrease cell survival. Thus, their effect does not favour remyelination; this is consistent with the results of studies with rodent cells. In conclusion, protocols for the administration of oligodendrocyte lineage cells with the aim of repopulating oligodendroglial niches or repairing demyelinated axons should not include corticosteroids, given the evidence that the effects of these drugs may undermine the objectives of cell transplantation.

Spatial metabolic heterogeneity of oligodendrogliomas at single-cell resolution

Oligodendrogliomas are a type of rare and incurable gliomas whose metabolic profiles have yet to be fully examined. The present study examined the spatial differences in metabolic landscapes underlying oligodendrogliomas and should provide unique insights into the metabolic characteristics of these uncommon tumors. Single-cell RNA-sequencing expression profiles from 4044 oligodendroglioma cells derived from tumors resected from four locations frontal, temporal, parietal, and frontotemporoinsular) and in which 1p/19q co-deletion and IDH1 or IDH2 mutations were confirmed were computationally analyzed through a robust workflow to elucidate relative differences in metabolic pathway activities among the different locations. Dimensionality reduction using metabolic expression profiles exhibited clustering corresponding to each location subgroup. From the 80 metabolic pathways examined, over 70 pathways had significantly different activity scores between location subgroups. Further analysis of metabolic heterogeneity suggests that mitochondrial oxidative phosphorylation accounts for considerable metabolic variation within the same locations. Steroid and fatty acid metabolism pathways were also found to be major contributors to heterogeneity. Oligodendrogliomas display distinct spatial metabolic differences in addition to intra-location metabolic heterogeneity.

Low grade gliomas

Low grade gliomas concern grade I and grade II tumors. The only grade one tumor is the pilocytic astrocytoma. This is a well-defined tumor with characteristic histology, often accompanied by a cyst. GKNS has been used in surgically inaccessible tumors since 1994. More recently it has been demonstrated that the tumors are more treatment resistant in adults than in children. Grade II tumors include oligodendrogliomas and grade II diffuse astrocytomas. The standard treatment for oligodendrogliomas us total removal followed by fractionated radiotherapy. GKNS has been shown to be of benefit in smaller tumors which have not responded to other treatment. It may also have a role as an ancillary treatment in smaller Grade II astrocytomas.

Prognostic factors associated with survival in patients with anaplastic oligodendroglioma

Anaplastic oligodendroglioma is a rare disease with an inadequately understood prognosis. The aim of this study was to investigate factors associated with survival outcome in anaplastic oligodendroglioma patients. A population-based cohort study was conducted based on the Surveillance, Epidemiology, and End Results program. In total, 1899 patients with a histological diagnosis of anaplastic oligodendroglioma from 1973 to 2015 were included. Mean age at diagnosis was 49.2 years, and 56.19% were male. In our study, 62.40% of patients were married, and 87.05% were white. Most patients (90.42%) were diagnosed with anaplastic oligodendroglioma as their first malignant primary tumor, but 9.58% had a diagnosis of at least one other primary malignancy; 87.89% of patients had received cancer-directed surgery. Patients receiving surgery had a better prognosis for overall survival compared to those not receiving surgery after propensity score matching analysis (p<0.05). The overall 1-, 3-, 5-, and 10-year survival of anaplastic oligodendroglioma was 78.7%, 60%, 50.2%, and 36.2%, respectively. Kaplan-Meier analysis indicated that age, marital status, presence of multiple primary malignancies, and surgical treatment were associated with overall survival, whereas sex and race were not. Moreover, age at diagnosis of 52 years was calculated as an optimal cutoff value to distinguish better and worse overall survival. Multivariate Cox proportional hazard analysis indicated that older age (OR 1.040, 95%CI1.035-1.045), single patients (OR 1.293, 95%CI 1.103-1.515), and presence of multiple primary malignancies (OR 1.501, 95%CI 1.238-1.820) were significantly associated with worse overall survival, whereas surgery (OR 0.584, 95%CI 0.494-0.689) was associated with better overall survival. A nomogram predicting 5-, and 10-year survival probability for anaplastic oligodendroglioma was constructed based on these variables. In conclusion, age, marital status, presence of multiple primary malignancies, and surgical treatment were associated with survival of anaplastic oligodendroglioma.

Anaplastic oligodendroglioma metastasizing to the bone marrow: a unique case report and literature review

Oligodendrogliomas are a rare type of primary brain tumor. They are genetically defined as diffuse gliomas carrying mutation in isocitrate dehydrogenase type 1 (IDH1) or type 2 (IDH2) and codeletion of chromosomes 1p and 19q. The WHO grading system distinguishes two histopathologic grades of ODs: grade II (low-grade) and grade III (anaplastic oligodendroglioma or AO). These tumors rarely metastasize outside of central nervous system with only few cases reported in the literature. Here we present a case of an AO, which metastasized to the bone marrow and other sites within a year of diagnosis despite aggressive treatment measures. Our patient eventually succumbed to his disease, raising many questions about this rare condition, its natural course and optimal management strategy.

Multiple Extraneural Metastases of Anaplastic Oligodendroglioma

Oligodendrogliomas (ODGs) is a diffuse glial tumor that constitutes 4.2% of all brain tumors. Extraneural metastases, sometimes seen in glioblastoma multiforme, are extremely rare in ODG. In this report, we present a 63-year-old male patient who was diagnosed with Grade 3 ODG and had an intracranial mass resected in our clinic 4 years ago. The subject now presented with low back pain and was found to have widespread metastases. The prolongation of patient survival by current treatment regimens has revealed a growing number of ODG patients with metastases. We believe that back pain complaints in patients with ODG should be viewed as an indicator of metastasis.

A case report about oligodendrogliomas of the fourth ventricle

RATIONALE

Oligodendrogliomas are usually located in the frontal, parietal and the temporal lobe, with the ones in the fourth ventricle quite rare. Hence we want to introduce a case about the rare disease.

PATIENT CONCERNS

An eight-year old boy complained of progressive headache, dizziness and vomit for about 2 months. Then the slight ataxia was found by the physical examinations, with no sensory disturbances and other motor disturbances.

DIAGNOSES

Abnormal signals on the fourth ventricle were found by the preoperative brain computed tomography (CT) scan and magnetic resonance imaging (MRI) scan. So the patient accepted a gross total resection of the lesion with pathologically confirmed oligodendroglioma.

INTERVENTIONS

Radiotherapy was then delivered in 27 fractions at 2Gy per fraction after the operation, with one fraction daily for five days weekly. No other therapies were used for the patient.

OUTCOMES

The brain MRI was used for follow-up every three months until now when he has finished all therapies for more than one year. No progressive behaviors (for example, headache, dizziness, vomit and other symptoms about cerebellar tonsillar hernia) or images have been presented. And the follow-up will be continued.

LESSONS

Although oligodendrogliomas are usually located in the frontal lobe, with the ones of fourth ventricle extremely rare, they must be kept in mind all times. Treatments applied to our case may be provided as a reference for clinicians. Furthermore, the maximal range of resection, histologically proved oligodendroglioma and the 1p/19q loss of heterozygosity are associated with favorable prognosis.

Lactate stimulates CA IX expression in normoxic cancer cells

Besides hypoxia, other factors and molecules such as lactate, succinate, and reactive oxygen species activate transcription factor hypoxia-inducible factor-1 (HIF-1) even in normoxia. One of the main target gene products of HIF-1 is carbonic anhydrase IX (CA IX). CA IX is overexpressed in many tumors and serves as prognostic factor for hypoxic, aggressive and malignant cancers. CA IX is also induced in normoxia in high cell density. In this study, we observed that lactate induces CA IX expression in normoxic cancer cells in vitro and in vivo. We further evidenced that participation of both HIF-1 and specificity protein 1 (SP1) transcription factors is crucial for lactate-driven normoxic induction of the CA9 gene. By inducing CA IX, lactate can facilitate the maintenance of cancer cell aggressive behavior in normoxia.

Osteosclerosis Secondary to Metastatic Oligodendroglioma

This paper reviews a case of metastatic 1p/19q codeleted oligodendrioglioma causing diffuse osteosclerosis and pain. Primary central nervous system (CNS) tumors rarely metastasize outside the CNS, and metastatic oligodendroglioma is rarer still. The patient in this study had relief of pain after being treated with temozolomide. We discuss this rare presentation and potential treatment options, and review the literature in regards to metastatic oligodendrogliomas.

Phase II trial of pre-irradiation and concurrent temozolomide in patients with newly diagnosed anaplastic oligodendrogliomas and mixed anaplastic oligoastrocytomas: long term results of RTOG BR0131

We report on the long-term results of a phase II study of pre-irradiation temozolomide followed by concurrent temozolomide and radiotherapy (RT) in patients with newly diagnosed anaplastic oligodendroglioma (AO) and mixed anaplastic oligoastrocytoma. Pre-RT temozolomide was given for up to 6 cycles. RT with concurrent temozolomide was administered to patients with less than a complete radiographic response. Forty eligible patients were entered and 32 completed protocol treatment. With a median follow-up time of 8.7 years (range 1.1-10.1), median progression-free survival (PFS) is 5.8 years (95 % CI 2.0, NR) and median overall survival (OS) has not been reached (5.9, NR). 1p/19q data are available in 37 cases; 23 tumors had codeletion while 14 tumors had no loss or loss of only 1p or 19q (non-codeleted). In codeleted patients, 9 patients have progressed and 4 have died; neither median PFS nor OS have been reached and two patients who received only pre-RT temozolomide and no RT have remained progression-free for over 7 years. 3-year PFS and 6-year OS are 78 % (95 % CI 61-95 %) and 83 % (95 % CI 67-98 %), respectively. Codeleted patients show a trend towards improved 6-year survival when compared to the codeleted procarbazine/CCNU/vincristrine (PCV) and RT cohort in RTOG 9402 (67 %, 95 % CI 55-79 %). For non-codeleted patients, median PFS and OS are 1.3 and 5.8 years, respectively. These updated results suggest that the regimen of dose intense, pre-RT temozolomide followed by concurrent RT/temozolomide has significant activity, particularly in patients with 1p/19q codeleted AOs and MAOs.

Magnetic resonance susceptibility weighted imaging in neurosurgery: current applications and future perspectives

Susceptibility weighted imaging (SWI) is a relatively new imaging technique. Its high sensitivity to hemorrhagic components and ability to depict microvasculature by means of susceptibility effects within the veins allow for the accurate detection, grading, and monitoring of brain tumors. This imaging modality can also detect changes in blood flow to monitor stroke recovery and reveal specific subtypes of vascular malformations. In addition, small punctate lesions can be demonstrated with SWI, suggesting diffuse axonal injury, and the location of these lesions can help predict neurological outcome in patients. This imaging technique is also beneficial for applications in functional neurosurgery given its ability to clearly depict and differentiate deep midbrain nuclei and close submillimeter veins, both of which are necessary for presurgical planning of deep brain stimulation. By exploiting the magnetic susceptibilities of substances within the body, such as deoxyhemoglobin, calcium, and iron, SWI can clearly visualize the vasculature and hemorrhagic components even without the use of contrast agents. The high sensitivity of SWI relative to other imaging techniques in showing tumor vasculature and microhemorrhages suggests that it is an effective imaging modality that provides additional information not shown using conventional MRI. Despite SWI's clinical advantages, its implementation in MRI protocols is still far from consistent in clinical usage. To develop a deeper appreciation for SWI, the authors here review the clinical applications in 4 major fields of neurosurgery: neurooncology, vascular neurosurgery, neurotraumatology, and functional neurosurgery. Finally, they address the limitations of and future perspectives on SWI in neurosurgery.

Brainstem oligodendroglial tumors in children: two case reports and review of literatures

PURPOSE

There is little information on pediatric oligodendroglial tumor located in the brainstem because of its rarity.

METHODS

Here, we present two pediatric cases of pontine oligodendroglial tumors with radiological findings atypical for diffuse intrinsic pontine glioma.

RESULTS

The first patient was an 8-year-old boy. Brain magnetic resonance imaging (MRI) demonstrated diffuse high-intensity changes in the pons, left middle cerebellar peduncle, and part of the left cerebellar hemisphere on T2-weighted and fluid-attenuated inversion recovery images, with an enhanced spot lesion in the left cerebellar hemisphere. The pathological diagnosis was anaplastic oligodendroglioma, and we identified a mutation in histone H3.3 in the tumor specimen. He succumbed to massive disseminated relapse 7 months from diagnosis despite local radiation therapy. The second patient, a 2-year-old girl, was diagnosed with oligoastrocytoma. Brain MRI revealed a large mass in her rostral pons extended to the fourth ventricle with obstructive hydrocephalus. The tumor recurred with intracranial dissemination 56 months post-surgery.

CONCLUSIONS

Pediatric brainstem oligodendroglial tumors can include histone H3.3-mutated tumors and have a tendency to disseminate throughout the neuroaxis at the time of relapse.

Multicystic oligodendroglioma with calvarial destruction

Context:

Calvarial erosion is known to occur with some superficially located tumors. Very few case reports of calvarial erosion associated with oligodendroglioma are reported in the literature, but calvarial destruction with oligodendroglioma is very rare.

Aim:

To report an unusual case of multicystic frontoparietal oligodendroglioma with destruction of the calvaria and scalp involvement in the absence of prior surgery or radiation.

Materials and Methods:

A 30-year-old male presented with the history of left focal seizure with secondary generalization for last three to four years along with left sided weakness for the past one month. There was history of slowly progressive decreased vision in both eyes leading to complete blindness in both eyes for the past one month. On neurological examination, patient had left hemiparesis of grade-2/5 with perception of light absent in both eyes. Fundus examination revealed bilateral optic atrophy. Magnetic resonance imaging (MRI) of the brain showed a large supratentorial heterogenous multicystic ring enhancing mass lesion involving right frontal lobe, right frontotemporal opercular region, and posteriorly abutting the central sulcus and anteriorly destroying the calvaria. Patient underwent right frontoparietal craniotomy and near total excision of tumor. Histopathological examination revealed oligodendroglioma WHO grade-2. Patient received postoperative chemoradiotherapy.

Results:

At nine month follow-up patient neurological status was same and his seizure was controlled on single AED. There was no recurrence of seizure at nine month of follow-up.

Conclusions:

Calvarial destruction in association with extra and intra axial neoplasm should include oligodendroglioma especially in patients with long history of symptoms, although calvarial destruction is very rare. However, the final diagnosis is established by means of histopathological examination.

Neurosurgical treatment of oligodendroglial tumors in children and adolescents: a single-institution series of 35 consecutive patients

OBJECT

The object of this study was to delineate long-term results of the surgical treatment of pediatric CNS tumors classified as oligodendroglioma (OD) or oligoastrocytoma (OA) WHO Grade II or III.

METHODS

A cohort of 45 consecutive patients 19 years or younger who had undergone primary resection of CNS tumors originally described as oligodendroglial during the years 1970-2009 at a single institution were reviewed in this retrospective study of surgical morbidity, mortality, and academic achievement and/or work participation. Gross motor function and activities of daily living were scored using the Barthel Index (BI).

RESULTS

Patient records for 35 consecutive children and adolescents who had undergone resection for an OA (17 patients) or OD (18 patients) were included in this study. Of the 35 patients, 12 were in the 1st decade of life at the first surgery, whereas 23 were in the 2nd decade. The male/female ratio was 1.19 (19/16). No patient was lost to follow-up. The tumor was localized to the supratentorial compartment in 33 patients, the posterior fossa in 1 patient, and the cervical medulla in 1 patient. Twenty-four tumors were considered to be WHO Grade II, and 11 were classified as WHO Grade III. Among these latter lesions were 2 tumors initially classified as WHO Grade II and later reclassified as WHO Grade III following repeat surgery. Fifty-four tumor resections were performed. Two patients underwent repeat tumor resection within 5 days of the initial procedure, after MRI confirmed residual tumor. Another 10 patients underwent a second resection because of clinical deterioration and progressive disease at time points ranging from 1 month to 10 years after the initial operation. Six patients underwent a third resection, and 1 patient underwent a fourth excision following tumor dissemination to the spinal canal. Sixteen (46%) of the 35 children received adjuvant therapy: 7, fractionated radiotherapy; 4, chemotherapy; and 5, both fractionated radiotherapy and chemotherapy. One patient with primary supratentorial disease experienced clinically malignant development with widespread intraspinal dissemination 9 years after initial treatment. Only 2 patients needed treatment for persistent hydrocephalus. In this series there was no surgical mortality, which was defined as death within 30 days of resection. However, 12 patients in the study, with follow-up times from 1 month to 33 years, died. Twenty-three patients, with follow-up times from 4 to 31 years, remained alive. Among these survivors, the BI was 100 (normal) in 22 patients and 80 in 1 patient. Nineteen patients had full- or part-time work or were in normal school programs.

CONCLUSIONS

Pediatric oligodendroglial tumors are mainly localized to the supratentorial compartment and more often occur in the 2nd decade of life rather than the 1st. Two-thirds of the patients remained alive after follow-ups from 4 to 31 years. Twelve children succumbed to their disease, 9 of them within 3 years of resection despite combined treatment with radio- and chemotherapy. Three of them remained alive from 9 to 33 years after primary resection. Among the 23 survivors, a stable, very long-term result was attainable in at least 20. Five-, 10-, 20-, and 30-year overall survival in patients with Grade II tumors was 92%, 92%, 92%, and 88%, respectively.

Magnetic resonance imaging volumetric assessment of the extent of contrast enhancement and resection in oligodendroglial tumors

OBJECT

Oligodendrogliomas that enhance on MR images are associated with poor prognosis. However, the importance of the volume of enhancing tumor tissue, and the extent of its resection, is uncertain. The authors examined the prognostic significance of preoperative and residual postoperative enhancing tissue volumes in a large single-center series of patients with oligodendroglioma. They also examined the relationship between enhancement and characteristic genetic signatures in oligodendroglial tumors, specifically deletion of 1p and 19q (del 1p/19q).

METHODS

The authors retrospectively analyzed 100 consecutive cases of oligodendroglioma involving patients who had undergone T1-weighted gadolinium-enhanced MRI at diagnosis and immediately after initial surgical intervention. The presence of preoperative enhancement was determined by consensus. Preoperative and residual postoperative volumes were measured using a quantitative, semiautomated method by a single blinded observer. Intrarater reliability for preoperative volumes was confirmed by remeasurement in a subset of patients 3 months later. Intrarater and interrater reliability for residual postoperative volumes was confirmed by remeasurement of these volumes by both the original and a second blinded observer. Multivariate analysis was used to assess the influence of contrast enhancement at diagnosis and the volume of pre- and postoperative contrast-enhancing tumor tissue on time to relapse (TTR) and overall survival (OS), while controlling for confounding clinical, pathological, and genetic factors.

RESULTS

Sixty-three of 100 patients had enhancing tumors at initial presentation. Presence of contrast enhancement at diagnosis was related to reduced TTR and OS on univariate analysis but was not significantly related on multivariate analysis. In enhancing tumors, however, greater initial volume of enhancing tissue correlated with shortened TTR (p = 0.00070). Reduced postoperative residual enhancing volume and a relatively greater resection of enhancing tissue correlated with longer OS (p = 0.0012 and 0.0041, respectively). Interestingly, patients in whom 100% of enhancing tumor was resected had significantly longer TTR (174 vs 64 weeks) and OS (392 vs 135 weeks) than those with any residual enhancing tumor postoperatively. This prognostic benefit was not consistently maintained with greater than 90% or even greater than 95% resection of enhancing tissue. There was no relationship between presence or volume of enhancement and del 1p/19q.

CONCLUSIONS

In enhancing oligodendrogliomas, completely resecting enhancing tissue independently improves outcome, irrespective of histological grade or genetic status. This finding supports aggressive resection and may impact treatment planning for patients with these tumors.

Hypoxia-inducible factor-1-regulated protein expression and oligodendroglioma patient outcome: comparison with established biomarkers and preoperative UCSF low-grade scoring system

Methods for predicting outcome for patients with oligodendrogliomas and anaplastic oligodendrogliomas (AOs) are limited. Hypoxia-inducible factor-1α (HIF-1α) controls many proteins involved in glycolysis and angiogenesis including VEGF, Glut-1, and CA-IX. We examined whether expression of HIF-1α and other hypoxia-regulated molecules (HRM) can predict overall (OS) and progression-free (PFS) survival. We correlated these data with more established biomarkers and a published preoperative scoring system. We prospectively collected tissue samples and followed outcomes of 50 patients with oligodendrogliomas and 32 with AOs. Tumor tissues were stained for measures of proliferative index, microvascular density, IDH-1 mutational status, and HRMs. We retrospectively analyzed preoperative imaging and clinical data based on the UCSF Scoring System (good prognostic indicators: Karnofsky Performance Scale (KPS) score > 80, age < 50 years, tumor diameter < 4 cm, noneloquent tumor location) and correlated these with immunohistochemical markers, 1p19q chromosomal status, and compared both with patient PFS and OS. Mean follow-up was 85.6 ± 41.4 months. HRMs showed higher expression in AOs than in oligodendrogliomas. Both 1p19q codeletion and IDH-1 mutation predict outcome of patients with both oligodendroglioma and AO. The UCSF score is a strong predictor for oligodendrogliomas patient outcome and is strengthened by IDH-1 and 1p19q status. Glut-1 may be useful in predicting PFS in AOs. Proliferation index >5 for oligodendrogliomas and KPS ≤ 80 for AOs predict a worse prognosis. Immunohistochemical markers of HRMs show a significantly higher expression in anaplastic variants of oligodendrogliomas and may contribute to the prediction of survival in these patients.

Imaging tumors of the pediatric central nervous system

Primary tumors of the central nervous system (CNS) are the second most common neoplasms in children and the leading cause of death in this patient population. The primary objective of this article is to describe the most common pediatric brain tumors and to offer an overview of their respective imaging features, primarily on magnetic resonance imaging. Precise anatomic characterization is essential for developing an appropriate differential diagnosis. Once equipped with this critical information, physicians should be better able to make firm diagnoses, leading to improved disease management and patient outcomes in the setting of CNS tumors of childhood.

Prognostic variables in oligodendroglial tumors: a single-institution study of 95 cases

We analyzed the relationships among clinical variables, histology, 1p/19q status, and outcome in 95 patients with oligodendroglial tumors. The study enrolled adult patients who underwent first-time surgery for a supratentorial oligodendroglial tumor at Oslo University Hospital, Rikshospitalet. Tumors were: 27 oligodendrogliomas, WHO grade II; 32 oligoastrocytomas, WHO grade II; 16 anaplastic oligodendrogliomas, WHO grade III; 14 anaplastic oligoastrocytomas, WHO grade III; and 6 glioblastomas with a major oligodendroglial component, WHO grade IV. The clinical files were reviewed. Three neuropathologists evaluated the histological slides independently. Loss-of-heterozygosity analysis for 1p and 19q was performed by PCR. Favorable prognostic factors from univariate analyses included seizures as presenting symptom, female sex, location in the frontal lobe, low WHO grade, classic histology, absence of gemistocytic cells, and combined 1p/19q loss. Solitary 19q loss was a negative prognostic marker. 1p/19q status was of prognostic significance in both tumors with classic and nonclassic oligodendroglial histology. In the multivariate analysis, WHO grade II (P< .001), frontal tumor location (P= .002), and combined 1p/19q loss (P< .001) remained favorable prognostic variables. Our results suggest that tumor location, WHO grade, and 1p/19q status are important independent variables associated with survival in oligodendroglial tumors. The study suggests that solitary 19q loss is a negative prognostic variable and that 1p/19q loss is associated with prolonged survival also in oligodendroglial tumors without classic histology.

Anaplastic oligodendroglioma

Although uncommon, anaplastic oligodendrogliomas (AODs) are important to recognize, as they have unique molecular, histologic, and clinical features. Patients with new seizures or new focal neurologic deficits should be referred for brain MRI with contrast. If the MRI suggests a malignant glioma, maximal feasible tumor resection is advised for accurate diagnosis and for relief of tumor-related neurologic symptoms. Radiation therapy (XRT) is the most commonly prescribed postsurgical therapy for patients with AODs. The role and timing of adjuvant chemotherapy are less clear. Tumor responses to PCV (the combination of procarbazine, lomustine, and vincristine) and to temozolomide have been documented in patients with AODs. However, two prospective phase 3 trials in patients with newly diagnosed AOD have shown no difference in overall survival when PCV is added to XRT. Ongoing trials investigating the benefit of temozolomide plus XRT in patients with newly diagnosed AOD will inform about the value of this common practice. The recognition that 1p19q codeletion is a marker of oligodendroglial differentiation and the subsequent prospective confirmation of this marker's importance in predicting better prognosis have been critical discoveries. Tumors with intermediate oligodendroglial features or mixed astrocytic features should be referred for 1p19q assessment. Identification of 1p19q status is also required in clinical trials for patients with AOD, given the association of 1p19q codeletion with improved response to therapies and overall prognosis. There are not yet sufficient data to guide individual treatment planning based on 1p19q status, but several planned and ongoing trials will address this issue. Unfortunately, AOD remains a terminal brain cancer even with maximal therapies. As more therapeutic options become available and the full significance of molecular markers is understood, 1p19q and other markers are expected to help guide optimal antitumor therapies, and it is hoped that survival and function will improve for all patients with AOD.

The role of radiotherapy in the treatment of newly diagnosed supratentorial low-grade oligodendrogliomas: comparative analysis with immediate radiotherapy versus surgery alone

PURPOSE

The purpose of this study was to evaluate the role of immediate postoperative radiotherapy (RT) in adult patients with a low-grade oligodendroglioma (LODG).

MATERIALS AND METHODS

A total of 74 patients, older than 15 years, were treated in our institution between April 1990 and March 2006 for newly diagnosed LODGs. After surgery, 43 patients were treated with immediate RT with a total dose of 54~55.8 Gy with 1.8 Gy fractions (RT group) and 31 patients were followed with no adjuvant RT (OP group). All patients were closely observed until tumor progression or death with frequent work-ups including neurological examinations and MRI. Primary endpoints were overall survival and progression-free survival. The median follow-up duration of survivors was 6.2 years in the RT group and 5.8 years in the OP group.

RESULTS

Median progression-free survival was 13.2 years in the RT group and 4.6 years in the OP group; multivariate analysis confirmed improved outcome with the use of immediate RT (hazard ratio, 0.22; 95% confidence interval-CI, 0.09~0.55; p<0.001). Median overall survival was 14.9 years in the RT group and 9.8 years in the OP group; the use of adjuvant RT was also associated with a trend toward better overall survival after immediate RT based on multivariate analysis (hazard ratio, 0.3; 95% CI, 0.08~1.17; p=0.082). No severe RT related complications were observed.

CONCLUSION

Immediate RT following surgery appears to be an effective treatment modality for supratentorial LODGs. However, the potential benefit of adjuvant RT for overall survival needs to be tested prospectively in the future.

Age-incidence patterns of primary CNS tumors in children, adolescents, and adults in England

Around 25% of all tumors in those 0-14 years of age and 9% in those 15-24 years of age involve the CNS. They are the most common cause of cancer-related deaths in both age groups. In adults 25-84 years of age, the proportion of CNS tumors is 2%; 5-year overall survival is 10%-15%; and survivors have considerable morbidity. Comprehensive up-to-date population-based incidence data on these tumors are lacking. We present incidence rates for primary CNS tumors based on data derived from the high-quality national cancer registration system in England. A total of 54,336 CNS tumors of malignant, benign, and uncertain behavior were registered across the whole of England from 1995 through 2003. The age-standardized rates for all ages (0-84 years) was 9.21 per 100,000 person-years. This is higher than previously reported for England because it includes nonmalignant CNS tumors and hence gives a more accurate picture of burden of disease. The age-standardized rates for those 0-14 years of age, 15-24 years of age, and 25-84 years of age were 3.56, 3.26, and 14.57 per 100,000 person-years, respectively. In this article, we describe the changing patterns in the epidemiology of primary CNS tumors in these three age groups with respect to sex, tumor behavior, and histology using the current WHO classification. This information will provide a reference for future studies nationally and internationally and make comparisons relevant and meaningful.

Extraneural metastases of anaplastic oligodendroglial tumors

Extraneural metastases of malignant gliomas are rare. According to the literature, they tend to appear in glioblastoma patients, but are exceptionally rare in anaplastic oligodendroglioma. We report on an anaplastic oligodendroglioma and an anaplastic oligoastrocytoma that metastasized to cervical lymph nodes and bones. Both patients were women aged 54 and 30 years, and the metastases appeared following craniotomy. In the first patient, metastases to cervical lymph nodes developed one year after surgery, and, despite adjuvant therapy, recurred in the same location several times. Fine needle aspiration biopsy (FNAB) of the cervical lymph node prior to neck dissection suggested a possible metastatic primitive neuroepithelial tumor. In the second case, metastases to the sacrum and femur developed after surgery for a recurrent anaplastic oligoastrocytoma. Our two cases reconfirm a rare but definite ability not only of glioblastoma but also of anaplastic oligodendroglioma, namely to metastasize to extraneural sites. It is important to bear this in mind, particularly in cases when the history of primary brain tumor is unavailable. In such instances, the correct diagnosis of the metastatic lesion may be extremely difficult if not impossible.

Does radiosurgery have a role in the management of oligodendrogliomas?

Object

In this study the authors evaluated the role of stereotactic radiosurgery (SRS) in the management of progressive or newly diagnosed small-volume oligodendrogliomas. Tumor control, survival, and complications were assessed in patients with oligodendroglioma who underwent Gamma Knife radiosurgery as a primary or adjuvant procedure.

Methods

The authors retrospectively reviewed 30 patients with oligodendroglioma (12 Grade II and 18 Grade III) who underwent SRS between 1992 and June 2006 at the University of Pittsburgh. The median patient age was 43.2 years (range 10.8–75.4 years). Twenty-four patients had previously undergone resection of the tumor, whereas tumors in 6 were diagnosed based on biopsy findings. The SRS was performed in 25 patients who had imaging-defined tumor progression despite prior fractionated radiation (22 patients) and/or chemotherapy (20 patients). The median target volume was 15.4 cm3 (range 0.07–48.7 cm3) and the median margin dose was 14.5 Gy (range 11–20 Gy).

Results

At an average of 39.2 months of follow-up (range 12–133 months), 17 patients were dead and 13 were living. The overall survival rates from diagnosis to 5 and 10 years were 90.9 and 68.2%, respectively, for Grade II and 52.1% at 5 years and 26.1% at 10 years for Grade III. Factors associated with an improved progression-free survival included lower tumor grade and smaller tumor volume. In 13 patients who had loss of heterozygosity testing, patients with 1p19q loss of heterozygosity had a significantly improved survival after diagnosis (p = 0.04).

Conclusions

The SRS modality is a minimally invasive additional option for patients with residual or recurrent oligodendrogliomas. It may also be considered as an alternative to initial resection in small-volume tumors located in the cortical brain region.

Phase II trial of preirradiation and concurrent temozolomide in patients with newly diagnosed anaplastic oligodendrogliomas and mixed anaplastic oligoastrocytomas: RTOG BR0131

The primary objectives of this phase II study were to evaluate the use of preirradiation temozolomide followed by concurrent temozolomide and radiotherapy (RT) in patients with newly diagnosed anaplastic oligodendroglioma (AO) and mixed anaplastic oligoastrocytoma (MOA). Preirradiation temozolomide (150 mg/m(2)/day) was given on a 7-day-on/7-day-off schedule for up to six cycles. The primary end point was the response rate during the 6-month, pre-RT chemotherapy. Tumor tissue was analyzed for the presence of chromosomal deletions on 1p and 19q and for MGMT-promoter methylation. Forty-two patients were enrolled; 39 were eligible. The objective response rate was 32% (6% [complete response, CR], 26% [partial response PR]), and the rate of progression during pre-RT chemotherapy was 10%. The worst nonhematological toxicity was grade 4 in three patients (8%). Twenty-two patients completed concurrent chemotherapy and RT. There were no grade 4 nonhematological toxicities during the concurrent chemotherapy and RT. Seventeen of 28 (60.7%) evaluable cases had codeletion of 1p/19q; all 17 were free from progression at 6 months. Sixteen of 20 (80%) evaluable cases had MGMT-promoter methylation; all 16 were free from progression at 6 months. In conclusion, the rate of progression of 10% during pre-RT temozolomide chemotherapy for newly diagnosed AO and MAO compared favorably with prior experience with pre-RT PCV chemotherapy (20% in RTOG 9402). The toxicity of the dose-intense pre-RT regimen used in this study may warrant evaluation of other, less intense dosing strategies. Future studies will need to prospectively stratify patients according to the presence of deletions of chromosomes 1p and 19q.

Extraneural metastases of anaplastic oligodendroglioma

Extraneural metastases from primary central nervous system (CNS) tumors are unusual, and glioblastomas and medulloblastomas constitute the majority of these. That oligodendroglioma frequently seeds within the CNS is well known. However, extraneural metastases of anaplastic oligodendroglioma are rare. We report a 50-year-old woman who developed multiple lung and liver metastases 28 months after resection of a temporal lobe anaplastic oligodendroglioma.

Molecular pathogenesis of adult brain tumors and the role of stem cells

Primary brain tumors consist of neoplasms with varied molecular defects, morphologic phenotypes, and clinical outcomes. The genetic and signaling abnormalities involved in tumor initiation and progression of the most prevalent adult primary brain tumors, including gliomas, meningiomas, and medulloblastomas, are described in this article. The current understanding of the cell-of-origin of these neoplasms is reviewed, which suggests that the malignant phenotype is propelled by cells with stem-like qualities. A comprehensive understanding of the molecular basis of transformation and the cell-of-origin of these neoplasms will enable the formulation of more targeted treatment alternatives that could improve survival and quality of life.

Malignant predominantly minigemistocytic glioma in two infants: a distinctive glioma variant?

We report unusual distinctive histopathological features in malignant supratentorial tumours of two infants (patient 1: congenital, patient 2: 30 months). Both patients had paraventricularly located well-delineated tumours. Gross total resection could be performed and postoperative chemotherapy was administered. At the last follow-up, 18 (patient 1) and 10 months (patient 2) postoperatively, both patients were in continuous complete remission. Histologically, both tumours were characterized by high cellular density and monomorphic appearance. Tumour cells were small to medium-sized and the majority of cells showed a distinctive minigemistocytic shape. A small fraction of cells lacked a distinct cytoplasm. Mitotic figures were abundant, tumour necrosis and hypertrophic vascular proliferations were absent. Immunohistochemically, the tumour cells expressed glial (GFAP, S100) and focally neuronal (NFP) proteins. Comparative genomic hybridization showed few, dissimilar chromosomal aberrations in the two tumours. Although sharp demarcation and monomorphic architecture of both tumours are reminiscent of a primitive neuroectodermal tumour, cytological and immunohistochemical glial differentiation refer to a glial tumour origin. To our knowledge the histopathological features of the described tumours do not correspond unequivocally to any established glioma variant and could represent a distinctive new glioma subtype.

Frontal Anaplastic Oligodendroglioma Showing Multi-organ Metastases After a Long Clinical Course-Case Report-

A 17-year-old woman presented with an anaplastic oligodendroglioma manifesting as generalized seizure. Neuroimaging studies revealed a right frontal tumor. Histological examinations of biopsy specimens revealed that the tumor was oligodendroglial in nature. Total resection was repeated four times, and malignant change was evident within the tissues. The final diagnosis was anaplastic oligodendroglioma. Despite irradiation, combination chemotherapy, and interstitial hyperthermia, the tumor grew rapidly but was confined to the cavity created by previous removal operations. She suffered bone pain in the last 3 months of her life, when neuroimaging examinations disclosed multiple bone lesions. She died at the age of 29 years. At autopsy, generalized metastases from the tumor were identified at various sites, including the dura mater covering the frontal lobes and thoracic cord, cavernous sinus, tuberculum sellae, spleen, liver, pancreas, lungs, paratracheal lymph nodes, vertebral bodies, ribs, sternum, pelvis, dorsal root ganglia, and iliopsoas muscle. This rare case of cerebral anaplastic oligodendroglioma developed in adolescence, and rapid hematogenous spread of the glioma cells into the systemic organs occurred after a relatively long clinical course.

Oligodendroglial tumors

Oligodendroglial tumors represent approximately 4-7% of all gliomas; however, in some series the incidence has been reported to be as high as 10-20% because of improved histological appreciation and recently recognized molecular signatures. Oligodendroglial tumors are classified as being low-grade oligodendroglial tumors, high-grade anaplastic oligodendroglial tumors or mixed oligo-astrocytic tumors. The mixed tumors can again be low-grade or high-grade. The recent European Organization for Research and Treatment of Cancer and Radiation Therapy Oncology Group randomized trials have provided level 1 evidence regarding the best management of these tumors. This review provides an overview of oligodendroglial tumors and discusses contemporary and evolving treatment strategies.

Proposal of a scoring scale as a survival predictor in intracranial oligodendrogliomas

INTRODUCTION

Histological, clinical and radiological features, and molecular genetic analysis are among the factors that have been considered in defining the prognosis of oligodendrogliomas (OD), but they have yielded conflicting results. The purpose of this study was to test out a scoring scale based on clinical, radiological, pathological and molecular features.

MATERIAL AND METHOD

To identify factors with prognostic significance, we analyzed 87 treated patients with a histological diagnosis of OD. Of the parameters analyzed, age, onset, clinical status, radiological enhancement, histological necrosis, mitosis and chromosomal anomalies emerged as significant prognosis factors using univariate analysis. Multivariate analysis revealed age and chromosomal anomalies as independent factors of survival.

RESULTS

The factors with a significant prognostic value were combined to determine which grouping factors best predict outcome. The proposed score is a pure number resulting from a combination of: 2 major factors: age and chromosomal anomalies (scored 3-0); 5 minor factors: onset, clinical examination, necrosis, mitoses (scored 1-0), and radiological enhancement (scored 2-0). According to our scale, 10 survival curves were produced for overall survival. Recursive partitioning of patients with the nearest score and outcome produced four groups with a significant difference in survival (p=10(-5)). The power of both the scale and the partitioned groups for predicting outcome was more accurate than the WHO and St Anne grading systems, and the molecular sub-classification.

CONCLUSIONS

Our scale is a plausible way of classifying patients harboring intracranial OD according to expected survival.

From the archives of the AFIP: Oligodendroglioma and its variants: radiologic-pathologic correlation

Oligodendroglioma is the third most common glial neoplasm and most commonly arises in the frontal lobe. It occurs in males more frequently, and the peak manifestation is during the 5th and 6th decades. Children are affected much less commonly. The clinical presentation is often of several years duration with most patients presenting with seizures, reflecting the strong predilection of this tumor to involve the cortical gray matter. Current histopathologic classification schemes recognize two main types of tumors: well-differentiated oligodendroglioma and its anaplastic variant. Less commonly, neoplastic mixtures of both oligodendroglial and astrocytic components occur and are termed oligoastrocytomas, with both well-differentiated and anaplastic forms. Surgical resection is the mainstay of initial treatment, and many patients experience a long progression-free period. Recent genotyping has revealed chromosomal loss of 1p and 19q as a genetic signature in most oligodendrogliomas, and these tumors respond favorably to chemotherapy. Hence, radiation therapy is now generally reserved for partially resected tumors and cases that failed to benefit from chemotherapy. At cross-sectional imaging, the tumor characteristically involves the cortical gray matter and frequently contains calcification. Robust enhancement is not a common feature and suggests transformation to a higher histologic grade. Advanced magnetic resonance imaging techniques and metabolic imaging play increasingly important roles in both pre- and postoperative assessment of these complex neoplasms.

Oligodendroglioma: clinical study and survival analysis correlated with chromosomal anomalies

Object

Demonstration of the loss of chromosomes 1p and 19q in the presence of a brain neoplasm marks the emergence of genotype as a prognostic indicator. The authors report gene expression data for oligodendroglioma and correlate genotype with response to therapy. Gene expression subgroups may represent distinct types of disease.

Methods

Eighty-seven cases of supratentorial oligodendroglioma were selected from 145 cases treated in a single center between January 1990 and December 2001. Fluorescence in situ hybridization was used to determine the status of chromosomes 1p and 19q. Parameters evaluated included clinical data and radiological and histological features. Univariate and multivariate analyses were performed and a probability value less than 0.05 was considered significant.

The patients included 48 women and 39 men. The overall mean age at presentation was 45 years for women and 36 years for men (p = 0.006). The univariate analysis identified the following as favorable prognostic factors: younger patient age (p = 10−5), female sex (p = 0.0025), seizure as a presenting symptom (p = 10−5), normal clinical examination (p = 10−5), absence of lesion enhancement on neuroimaging studies (p = 0.0231), lack of histological necrosis (p = 0.0003), absence of mitoses (p = 0.0014), 1p and 19q deletions (p = 0.0001), absence of recurrence (p = 0.0021), and adjuvant radiotherapy and/or chemotherapy (p = 10−5). The multivariate analysis identified patient age (p = 10−5) and chromosomal anomalies (p = 0.002) as independently linked to survival. Three molecular subtypes emerged: oligodendroglioma with 1p and 19q deletions, oligodendroglioma demonstrating polysomia and a lack of meaningful response to radiotherapy or chemotherapy, and oligodendroglioma with no 1p-9q deletion in which partial response was seen.

Conclusions

According to our data, oligodendrogliomas could be divided into three molecular subtypes. Although chemotherapy seems efficient for managing this tumor, additional studies should be conducted to compare the efficacy of radiotherapy and chemotherapy.

Les oligodendrogliomes supratentoriels de l’enfant

BACKGROUND AND PURPOSE

The goal of this study was to analyze the main aspects of oligodendrogliomas observed in children.

METHOD

The records of 35 children aged 15 years or younger (23 from Marseilles and 12 from Lyons) were reviewed. Clinical signs and symptoms, imaging findings (CT scan and pre- and post-operative MRI), extent of surgical resection, histology according to the WHO and Ste-Anne grading and survival were analysed. Considering all these factors, a statistical analyzis was undertaken in order to identify prognostic factors.

DISCUSSION AND CONCLUSION

Oligodendrogliomas are rare tumors in children. The most important differential diagnosis to discuss is dysembryoplastic neuroepithelial tumor. Our study allowed us to distinguish several subgroups of patients with a different prognosis: thalamic tumors with a dismal prognosis versus hemispheric tumors. A group of cortical tumors we called "DNT-like" (hemispheric cortical tumor, isolated epilepsy, without neurological deficit and reased ICP, without edema and mass effect on MRI) with an excellent prognosis like the group with epilepsy. Histological grading (grade A/grade B and grade II/grade III) is also a prognostic factor.

Fractionated stereotactic radiation therapy in the management of primary oligodendroglioma and oligoastrocytoma

PURPOSE

To retrospectively analyze the outcomes and benefits from radiation therapy (RT) as a component of multimodal treatment for oligodendroglioma and oligoastrocytoma, assessing local control and survival rates and evaluating prognostic factors.

METHODS AND MATERIALS

We retrospectively reviewed 56 adult patients with supratentorial oligodendroglioma or oligoastrocytoma treated at our institution from January 1990 to December 2003 with fractionated stereotactic RT (FSRT).

RESULTS

Fractionated stereotactic RT was well tolerated in all patients, without side effects. Median survival and progression-free survival calculated from the initiation of radiotherapy were 48 months (range, 2-133 months) and 38 months (range, 2-132 months), respectively. Progression-free survival rates after radiation were 89% at 1 year and 52% at 5 years. Of 26 recurrences, 92% developed in field. With regard to histology, overall survival rates in the World Health Organization (WHO) Grade II group were 89% and 74% at 5 and 10 years, respectively. In patients with WHO Grade III tumors, overall survival rates at 5 and 10 years were 69% and 46%, respectively. No prognosticators could be identified for median survival and progression-free survival after radiotherapy. Median overall survival calculated from primary diagnosis was 77.5 months (range, 3-214 months). The Cox regression multivariate analysis for age and neurologic symptoms showed a significance of p = 0.003 for age and p = 0.037 for the presence of neurologic symptoms on overall survival since primary diagnosis.

CONCLUSIONS

Commonly, conventional conformal RT is applied in the treatment of brain tumors. In FSRT, the tumor volume can be irradiated with high doses, sparing volume of normal brain tissue. Our data are in accordance with survival times found in the literature. Ninety-two percent of all recurrences occurred within the defined target volume, confirming that reduction of the RT portals by the use of FSRT does not lead to an increased rate of recurrences at the field border or out of field. Fractionated stereotactic RT can therefore be implemented as an effective and safe modality in the therapy of primary oligodendroglioma and oligoastrocytoma.

Disseminating anaplastic brainstem oligodendroglioma associated with allelic loss in the tumor suppressor candidate region D19S246 of chromosome 19 mimicking an inflammatory central nervous system disease in a 9-year-old boy

We report the case of a 9-year-old boy clinically presenting with severe headache, vomiting, head retroflexion, nystagmus, and ataxia. Magnetic resonance imaging showed brainstem enlargement leading to the diagnosis of an inflammatory process. In addition, the clinical picture, a monocytic cerebrospinal fluid pleocytosis with elevated protein and lactate and serum IgM antibodies to Mycoplasma pneumoniae favored this diagnosis. Subsequently, corticosteroid treatment rapidly improved clinical symptoms, and lesions declined in subsequent neuroradiological examinations. However, 2 months later, fulminant disease progression led to brain death. Final neuroradiological examination favored meningoencephalitis. The autopsy revealed brain swelling and brainstem softening with a superficial gelatinous mass extending along the spinal cord. Finally, a disseminating anaplastic oligodendroglioma with allelic loss of the D19S246 tumor suppressor candidate locus of chromosome 19 was diagnosed. To our knowledge, this is the first case of a disseminating anaplastic brainstem oligodendroglioma associated with this specific allelic loss occurring in childhood.

[Extra-cranial anaplastic oligoastrocytoma development from a low-grade glioma]

Oligodendrogliomas are primary brain tumours derived from oligodendroglial cells, or precursors, and represent 2%-5% of brain tumours. This type of glioma has a favourable prognosis compared to other brain tumours. The treatment is multidisciplinary and is based on three therapeutic arms: surgery, radiotherapy and chemotherapy. We present a patient who had received treatment previously for a lowgrade glioma and who subsequently developed an anaplastic oligoastrocytoma in the same zone together with skull and extra-cranial involvement in the disease progression.

Impact of location on outcome in children with low-grade oligodendroglioma

BACKGROUND

Childhood low-grade oligodendroglioma (WHO grade II) are rare. No controlled pediatric study has been published, to generate high level evidence for the best treatment. Therefore, we retrospectively analyzed data available from pediatric patients.

PROCEDURE

We pooled data from two prospective German multicentre studies (HIT-DOK and HIT-LGG). Eligibility criteria were: (1) primary neoplasm, (2) histology of pure oligodendroglioma WHO grade II, (3) intracranial location, (4) age <18 years, (5) date of diagnosis: 1990-2002, (6) observation time >6 months. The outcome was analyzed by using the SPSS-software.

RESULTS

Nineteen boys and 13 girls were eligible (median age 10.3 years). The tumor locations included: 26 peripheral tumors (23 cerebral hemisphere, 3 cerebellum), and 6 central tumors (4 thalamus, 1 frontal mesencephalon, 1 basal ganglia). Resections were classified as complete in 18 (14 cerebral hemispheres, 3 cerebellum, 1 thalamus) and less than complete in 14 patients (3 subtotal resections, 8 partial resections, 3 biopsy). The 5-year event-free survival (EFS) and overall survival (OS) rates of all patients were 81.3 and 84.4%, respectively (median observation time 3.8 years). All of the 26 children with peripheral tumors were alive with no tumor progression, but five of six patients with central tumors died of disease (median time to death 1.6 years). This survival difference was statistically significant for EFS (P < 0.0001) and OS (P < 0.0001). The difference between completely resected versus incompletely resected tumors was far less striking (P > 0.06).

CONCLUSIONS

The outcome of children with centrally located low-grade oligodendroglioma is particularly poor, while tumors of the cerebral hemispheres and cerebellum carry an excellent prognosis, even with minor tumor resection.

Pathology and molecular genetics of oligodendroglial tumors

Oligodendroglial gliomas are second only to astrocytic gliomas in frequency. The lack of stringent diagnostic criteria cause high interobserver variation in regard to classification and grading of these tumors. Previous studies have described oligodendrogliomas with features that overlap with those of neurocytic tumors, thus further complicating diagnostic decisions. The increasing need for standardized diagnostic criteria in this subset of gliomas is emphasized by the benefit of adjuvant therapies in patients with anaplastic oligodendrogliomas. Characteristic chromosomal aberrations have been successfully determined for oligodendroglial tumors in recent years. In contrast to astrocytomas, however, no genes in the affected regions have been clearly linked to their pathogenesis. However, the molecular findings promise to be helpful for diagnostic and therapeutic decisions. This review compiles clinical, pathological, and molecular genetic findings on WHO grades II and III oligodendrogliomas and oligoastrocytomas.