Temozolomide as initial treatment for adults with low-grade oligodendrogliomas or oligoastrocytomas and correlation with chromosome 1p deletions

Prognostic impact of molecular markers in a series of 220 primary glioblastomas

BACKGROUND

In contrast to oligodendrogliomas, molecular predictors of prognosis have not been consistently found in glioblastomas. However, genetic studies show that glioblastomas consist of several genetic subtypes and raise the possibility that molecular alterations could be predictive of survival.

METHODS

A search for loss of heterozygosity (LOH) on chromosome 1p, 9p, 10q, 19q, EGFR (epidermal growth factor receptor), CDK4, and MDM2 (mouse double minute) amplifications, CDKN2A (INK4A/ARF) homozygous deletions, p53 expression, was performed in a series of 220 primary glioblastomas. The molecular alterations were then correlated with each other to identify distinct molecular pathways and with clinical parameters and the course of the disease to identify prognostic markers.

RESULTS

Nonrandom associations were found between EGFR amplification and LOH10q, LOH9p, and INK4A/ARF deletion, LOH1p and LOH19q, and MDM2 and CDK4 amplification, whereas mutual exclusions were found between p53 expression and EGFR amplification, LOH 9p/INK4A/ARF homozygous deletion, and MDM2 and CDK4 amplification. Age (P = 4.10(-5)) and performance status (P = .003) were the main predictors of outcome. In contrast, molecular markers were of limited impact: MDM2 amplification correlated with poor outcome on both univariate and multivariate analysis (P = .01) and EGFR amplification with good prognosis on multivariate analysis (P = .02).

CONCLUSION

Despite their limited prognostic impact, the genetic markers investigated here outline distinct molecular pathways involved in glioblastoma tumorigenesis and warrant broader molecular screening.

Low‐Grade Gliomas in Adults

Low-grade gliomas are a heterogeneous group of neoplasms usually encountered in younger patient populations. These tumors represent a unique challenge because most patients will survive a decade or more and may be at a higher risk for treatment-related complications. Clinical observations over the years have identified a subset of low-grade gliomas that tends to manifest more aggressive clinical behavior and require earlier, more aggressive intervention. Clinical and molecular parameters may allow better assessment of prognosis and application of risk-adjusted management strategies that may include resection, radiation, or chemotherapy. Improved methods of long-term cognitive and functional assessment are desperately needed in this patient population.

[Cerebral gliomas: imaging diagnosis and follow-up]

The management of gliomas evolves towards more aggressive strategies with a combination of surgery, radiotherapy and chemotherapy. Follow-up imaging based on morphological MRI, with simple and reproducible protocols, may be associated with functional MRI and spectroscopy. Baseline postsurgical MRI must be performed within the first three days. Follow-up examinations should be done 2 months after radiotherapy and during chemotherapy, usually after each cycle of two or three treatments. Continued follow-up after therapy is recommended to assess response and detect recurrences or therapeutic complications.

Treatment-related myelodysplasia/AML in a patient with a history of breast cancer and an oligodendroglioma treated with temozolomide: case study and review of the literature

The emergence of temozolomide as an effective alkylating agent with little acute toxicity or cumulative myelosuppression has led to protracted courses of chemotherapy for many patients with gliomas. Secondary, or treatment-related, myelodysplasia (t-MDS) and acute myelogenous leukemia (t-AML) are life-threatening complications of alkylating chemotherapy and have been reported in patients with primary brain tumors. We describe a case of temozolomide-related t-MDS/AML and discuss the clinical features of this condition. Administration of an alkylating agent in patient populations with long median survivals must be undertaken with an understanding of the potential for this treatment complication.

Progressive low-grade oligodendrogliomas: response to temozolomide and correlation between genetic profile and O6-methylguanine DNA methyltransferase protein expression

BACKGROUND

Loss of heterozygosity (LOH) on chromosomes 1p and 19q has been associated with chemosensitivity and improved prognosis in patients with oligodendrogliomas. The DNA repair enzyme O6-methylguanine DNA methyltransferase (MGMT) may induce resistance to DNA-alkylating agents. Recent studies demonstrated that temozolomide (TMZ), an oral alkylating agent, has efficacy in the treatment of patients with progressive, low-grade oligodendroglioma (LGO). However, to the authors' knowledge, limited data are available regarding the 1p/19q profile and its correlation with MGMT protein expression and response to treatment with DNA-alkylating drugs.

METHODS

Adult patients with magnetic resonance imaging (MRI) findings and/or clinical deterioration compatible with progressive LGO were eligible for the study if they were radiotherapy-naive. TMZ cycles were repeated every 28 days at a dose of 200 mg/m2 daily for 5 consecutive days. Clinical and MRI data were used to evaluate outcomes, and Kaplan-Meier estimates were used to assess the median time to tumor progression (TTP). The 1p/19q status was analyzed from paired tumor-blood DNA samples using polymerase chain reaction-based microsatellite analysis. MGMT protein expression was estimated semiquantitatively by immunohistochemistry using paraffin embedded tumor sections.

RESULTS

There were 28 patients who received treatment, and the median time from diagnosis to tumor progression was 33.5 months. The median number of TMZ cycles per patient was 12.5. Marked clinical improvements were recorded in 15 patients (54%), and objective responses were recorded in 17 patients (61%). The median TTP was 31 months, and the progression-free survival rate was 70% at 24 months. Loss of chromosome 1p and low MGMT protein expression were associated with objective response (P < .003 and P < .04, respectively).

CONCLUSIONS

TMZ was active in patients with progressive LGO, and their response to treatment was associated with 1p deletion and low MGMT protein expression. The authors suggest the possible use of MGMT immunostaining as a surrogate marker for predicting tumor chemosensitivity.

Radical surgery after chemotherapy: a new therapeutic strategy to envision in grade II glioma

While surgery is proned in low-grade glioma (LGG), the invasion of functional areas frequently prevents a complete resection. We report the first case of a patient operated on for a left frontal LGG, diagnosed because of seizures, with partial resection due to an invasion of the controlateral hemisphere. Chemotherapy enabled a regression of this controlateral extension. Postchemotherapy surgery performed with intraoperative functional mapping then allowed a complete resection, without sequelae. The patient has a normal socio-professional life, with no seizure. No other treatment was given. There was no recurrence, with a follow-up of 2 years since the second surgery (3.5 years since the first symptom). We propose a new therapeutic strategy in unresectable LGG, with preoperative chemotherapy, to make a radical surgery possible in a second step, while preserving the quality of life.

Recent advances in the treatment of oligodendrogliomas

The optimal treatment for patients with oligodendrogliomas is unknown, and current management strategies remain controversial. This past year, further exploration of the molecular genetics of the tumors and its prognostic implications for outcome, evaluation of the utility of positron emission tomography imaging, and the role of radiation and chemotherapy in the treatment of oligodendrogliomas have been reported. It is becoming increasingly apparent that oligodendrogliomas are several distinct diseases on a molecular level, and that key genetic derangements can signify a response to treatment and favorable outcome. The added contributions of recent publications consolidates these emerging impressions. Ultimately, the combination of improved imaging techniques, molecular profiling, and new therapies should result in improved outcome with reduced treatment-related toxicity for patients with newly diagnosed, progressive, and recurrent oligodendrogliomas.

New concepts in surgery of WHO grade II gliomas: functional brain mapping, connectionism and plasticity – a review

Despite a recent literature supporting the impact of surgery on the natural history of low-grade glioma (LGG), the indications of resection still remain a matter of debate, especially because of the frequent location of these tumors within eloquent brain areas - thus with a risk to induce a permanent postoperative deficit. Therefore, since the antagonist nature of this surgery is to perform the most extensive glioma removal possible, while preserving the function and the quality of life, new concepts were recently applied to LGG resection in order to optimize the benefit/risk ratio of the surgery.First, due to the development of functional mapping methods, namely perioperative neurofunctional imaging and intrasurgical direct electrical stimulation, the study of cortical functional organization is currently possible for each patient - in addition to an extensive neuropsychological assessment. Such knowledge is essential because of the inter-individual anatomo-functional variability, increased in tumors due to cerebral plasticity phenomena. Thus, brain mapping enables to envision and perform a resection according to individual functional boundaries.Second, since LGG invades not only cortical but also subcortical structures, and shows an infiltrative progression along the white matter tracts, new techniques of anatomical tracking and functional mapping of the subcortical white matter pathways were also used with the goal to study the individual effective connectivity - which needs imperatively to be preserved during the resection.Third, the better understanding of brain plasticity mechanisms, induced both by the slow-growing LGG and by the surgery itself, were equally studied in each patient and applied to the surgical strategy by incorporating individual dynamic potential of reorganization into the operative planning. The integration of these new concepts of individual functional mapping, connectivity and plastic potential to the surgery of LGG has allowed an extent of surgical indications, an optimization of the quality of resection (neuro-oncological benefit), and a minimization of the risk of sequelae (benefit on the quality of life). In addition, such a strategy has also fundamental applications, since it represents a new door to the connectionism and cerebral plasticity.

The impact of genotype on outcome in oligodendroglioma: validation of the loss of chromosome arm 1p as an important factor in clinical decision making

Object

Oligodendrogliomas are rare primary brain tumors. They comprise approximately 5 to 33% of all glial tumors but differ from astrocytomas by being associated with a more favorable prognosis, making their correct identification important. Allelic loss of chromosome arms 1p and 19q is found in a substantial subpopulation of tumors with an oligodendroglioma phenotype. Anaplastic oligodendrogliomas with allelic loss of 1p have been associated with chemosensitivity and a longer patient survival period.

Methods

Oligodendroglial neoplasms were studied using fluorescence in situ hybridization of formalin-fixed, paraffin-embedded tissue specimens; reference and target probe sets were used to map the telomeric regions of 1p and 19q. The results were correlated with the clinical characteristics of patients treated at our institution between 1993 and 2003.

Data obtained in 96 patients were analyzed. This included 63 patients (65.6%) with World Health Organization (WHO) Grade II oligodendroglioma, 22 (23%) with Grade III oligodendroglioma, and 11 (11.4%) with mixed oligoastrocytoma. Analysis of 1p in patients with pure oligodendroglioma revealed a loss of 1p in 42 patients (49.4%). In 46 of these patients 19q was lost and in 70 (82.3%) there was concordance for combined loss or retention of both 1p and 19q (p < 0.0001). Patients with oligodendroglioma in whom a loss of 1p was present fared significantly better, and this outcome was unrelated to the treatment modality or WHO grade, compared with patients in whom 1p was intact (p < 0.05).

Conclusions

To the authors’ knowledge, this study includes the largest published series of WHO Grade II oligodendroglioma and 1p analysis. The results suggest that the association between long-term survival and 1p loss in oligodendroglioma is unrelated to treatment. The authors of further prospective studies may better determine the true value of the allelic loss of 1p and its implication for clinical decision making.

An update on oligodendroglial neoplasms

PURPOSE OF REVIEW

The most widely accepted brain tumor classification system remains morphology-based but the increasing knowledge of the molecular pathogenesis of oligodendroglial tumors has spurred translational research yielding new diagnostic and therapeutic paradigms. These data have accumulated rapidly and, in combination with exciting new insights in the cellular origin of these tumors, necessitate a review.

RECENT FINDINGS

'Cancer stem cells' have been identified in gliomas. Further study of these cells will not only provide information on the cellular origin and pathogenesis of these tumors but may also give rise to new treatments that target a cell pool not amenable to current therapeutic strategies. Molecular tumor characteristics have been correlated with imaging findings, treatment response and prognosis. This has enabled neuro-oncologists to take a risk-stratified approach to patients with oligodendrogliomas that optimizes treatment efficacy and minimizes toxicity. Furthermore, more accurate epidemiological data have become available from population-based studies.

SUMMARY

In spite of remarkable progress over the last 15 years, these tumors remain incurable. The search for a cure has to go on, while currently available multidisciplinary treatments are refined.

Recent developments in the use of chemotherapy in brain tumours

Several recent studies have further clarified the role of chemotherapy in newly diagnosed anaplastic glioma. For newly diagnosed glioblastoma, combined daily radiotherapy with daily temozolomide followed by six cycles of adjuvant temozolomide improves overall survival. This benefit is especially observed in patients with a methylated promotor of the MGMT gene which encodes an alkyltransferase; this observation however, needs confirmation. Although oligodendroglial tumours are sensitive to chemotherapy, classical adjuvant nitrosourea-based chemotherapy does not improve overall survival in newly diagnosed anaplastic oligodendroglioma, even in the subset of 1p/19q loss tumours. It may increase progression-free survival however, and further studies must show if combined modality treatment with daily chemotherapy during radiotherapy increases survival. Trials exploring the role of chemotherapy in low-grade glioma are ongoing. No standard chemotherapy is currently available for highly anaplastic glioma failing first-line temozolomide-based therapy.

In vivo uptake and metabolism of alpha-[11C]methyl-L-tryptophan in human brain tumors

Abnormal metabolism of tryptophan has been implicated in modulation of tumor cell proliferation and immunoresistance. alpha-[(11)C]Methyl-L-tryptophan (AMT) is a PET tracer to measure cerebral tryptophan metabolism in vivo. In the present study, we have measured tumor tryptophan uptake in 40 patients with primary brain tumors using AMT PET and standard uptake values (SUV). Tryptophan metabolism was further quantified in 23 patients using blood input data. Estimates of the volume of distribution (VD') and the metabolic rate constant (k(3)') were calculated and related to magnetic resonance imaging (MRI) and histology findings. All grade II to IV gliomas and glioneuronal tumors showed increased AMT SUV, including all recurrent/residual tumors. Gadolinium enhancement on MRI was associated with high VD' values, suggesting impaired blood-brain barrier, while k(3)' values were not related to contrast enhancement. Low-grade astrocytic gliomas showed increased tryptophan metabolism, as measured by k(3)'. In contrast, oligodendrogliomas showed high VD' values but lower k(3)' as compared with normal cortex. In astrocytic tumors, low grade was associated with high k(3)' and lower VD', while high-grade tumors showed the reverse pattern. The findings show high AMT uptake in primary and residual/recurrent gliomas and glioneuronal tumors. Increased AMT uptake can be due to increased metabolism of tryptophan and/or high volume of distribution, depending on tumor type and grade. High tryptophan metabolic rates in low-grade tumors may indicate activation of the kynurenine pathway, a mechanism regulating tumor cell growth. AMT PET might be a useful molecular imaging method to guide therapeutic approaches aimed at controlling tumor cell proliferation by acting on tryptophan metabolism.

Changing Paradigms—An Update on the Multidisciplinary Management of Malignant Glioma

Treatment of malignant glioma requires a multidisciplinary team. Treatment includes surgery, radiotherapy, and chemotherapy. Recently developed agents have demonstrated activity against recurrent malignant glioma and efficacy if given concurrently with radiotherapy in the upfront setting. Oligodendroglioma with 1p/19q deletions has been recognized as a distinct pathologic entity with particular sensitivity to radiotherapy and chemotherapy. Randomized trials have shown that early neoadjuvant or adjuvant administration of procarbazine, lomustine, and vincristine chemotherapy prolongs disease-free survival; however, it has no impact on overall survival. Temozolomide, a novel alkylating agent, has shown modest activity against recurrent glioma. In combination with radiotherapy in newly diagnosed patients with glioblastoma, temozolomide significantly prolongs survival. Molecular studies have demonstrated that the benefit is mainly observed in patients whose tumors have a methylated methylguanine methyltransferase gene promoter and are thus unable to repair some of the chemotherapy-induced DNA damage. For lower-grade glioma, the use of chemotherapy remains limited to recurrent disease, and first-line administration is the subject of ongoing clinical trials. Irinotecan and agents like gefitinib, erlotinib, and imatinib targeting the epidermal growth factor receptor and platelet-derived growth factor receptor have shown some promise in recurrent malignant glioma. This review summarizes recent developments, focusing on the clinical management of patients in daily neuro-oncology practice.

Quantitation of chromosome 1p and 19q deletions in glial tumours by interphase FISH on formalin-fixed paraffin-embedded tissue

Deletions on chromosomes 1p and 19q identify oligodendroglial tumours that are likely to have a complete response to some chemotherapy regimens and are associated with prolonged patient survival. Detection of these chromosomal alterations is becoming increasingly important in the evaluation of glial tumours. Interphase fluorescence in situ hybridisation (FISH) is one of a number of techniques for detecting deletions, and is an efficient method for screening large numbers of tumours. We used FISH to detect 1p and 19q deletions in formalin-fixed paraffin sections of 11 oligodendrogliomas, 11 oligoastrocytomas, two astrocytomas and four glioblastomas multiforme. 1p and 19q deletion and non-deletion ratios were tabulated in 200 nuclei in each tumour. We found considerable variation between tumours in the fraction of cells with deletions. This variation has not been reported previously and its clinical significance will be clarified with patient follow-up. There was little variation between regions within the same tumour.

Prognostic stratification of patients with anaplastic gliomas according to genetic profile

BACKGROUND

There is a need to improve the current, controversial, and poorly reproducible classification of anaplastic gliomas, which represent a highly heterogeneous entity in terms of survival.

METHODS

The impact of the most common genetic alterations on survival was investigated based on 156 anaplastic gliomas: Among the patients who were included, the gender ratio was 1.32, the median age was 45.5 years (range, 20-83 years), and the median Karnofsky performance status was 70 (range, 40-100). Genetic analysis included a search for loss of heterozygosity (LOH) on chromosomes 1p and 19q; amplification of chromosomes 9p and 10q and of the epidermal growth factor receptor (EGFR), cyclin-dependent kinase 4 (CDK4) and mouse double-minute (MDM2) genes; and p53 expression.

RESULTS

The median survival was 33.5 months, and the median progression-free survival was 15.8 months. In a univariate analysis, LOH on 1p and 19q was correlated with longer survival, whereas p53 expression, LOH on 9p, LOH on 10q, amplified EGFR, and deleted CDKN2A were correlated with shorter survival. LOH on 1p and 19q were associated with oligodendrogliomas, LOH on 10q was related to EGFR amplification, and LOH on 1p and 19q was mutually exclusive with EGFR amplification and LOH on 10q. In a multivariate analysis, the significant prognostic factors were age, histology, LOH on 1p and 19q, and P16/CDKN2A deletion. Recursive partitioning analysis (RPA) divided the whole group hierarchically into 3 distinct prognostic subgroups: Group A with 1p19q codeletion (median survival, 98 months), Group B with EGFR amplification (median survival, 17 months), and Group CC (median survival, 31 months), providing a basis for a genetically based prognostic subclassification for patients with Grade III gliomas.

CONCLUSIONS

The search for 1p19q codeletion and EGFR receptor amplification provides a simple, clinically relevant prognostic subclassification of grade III gliomas.

Low-grade gliomas: The debate continues

Low-grade gliomas (LGG) are a heterogeneous group of tumors that tend to occur primarily in young adults and children. They are indolent, progressive, and often undergo anaplastic transformation. The prognosis of these tumors is primarily affected by age and pathologic type. Many questions remain in the management of LGGs, including the role of surgical resection (ie, maximal tumor resection), the optimal timing of radiation (ie, postoperative vs at the time of tumor progression), and the role of chemotherapy (ie, salvage after radiotherapy, primary treatment after surgery, concurrent with radiotherapy). Further complicating treatment decisions are concerns about toxicity with any intervention because LGG patients can often lead a relatively normal existence for years with no intervention. In this article we review the pertinent LGG literature published over the past few years and its impact on the management of LGGs.

Two types of chromosome 1p losses with opposite significance in gliomas

Deletion of the short arm of chromosome 1 (1p) is considered a favorable prognostic factor in glial tumors. High-density array-comparative genomic hybridization analysis of 108 gliomas shows two distinct types of 1p deletions. Complete hemizygous losses of 1p, which are tightly associated with 19q loss and oligodendroglial phenotype, and partial 1p deletions mainly observed in astrocytic tumors and not associated with 19q loss. Whereas the first type predicts longer overall and progression-free survival (p < 0.0001), the second type has a pejorative prognostic value. Complete 1p-arm evaluation therefore is required to appreciate the real clinical significance of 1p loss in gliomas.

Temozolomide: a milestone in the pharmacotherapy of brain tumors

Temozolomide (TMZ) is an alkylating agent earlier approved for recurrent anaplastic astrocytoma and approved for the treatment of newly diagnosed glioblastoma in the USA and Europe in 2005. TMZ shows good blood–brain barrier penetration and exhibits a favorable side effect profile. Its key mode of action appears to be methylation at N7 and O6-positions of guanine. The level of expression and activity of the DNA repair enzyme O6-methylguanine DNA methyltransferase is thought to be a major predictor of response to TMZ. The demonstration of prolonged survival when TMZ was added to radiotherapy in the European Organisation for Research and Treatment of Cancer 26981/22981/NCIC CE.3 trial has been a breakthrough in the treatment of newly diagnosed glioblastoma. The early preliminary evidence for activity in recurrent malignant gliomas further resulted in a broad evaluation of TMZ for other tumors in neuro-oncology, mainly low-grade gliomas, brain metastases and primary cerebral lymphomas.

Low-grade gliomas: an update on pathology and therapy

Low-grade gliomas (LGG) are not benign neoplasms. Patients with LGG eventually die as a consequence of this disease. Although the survival of patients with LGG is better than that of patients with higher-grade tumours, many of the treatments can produce or contribute to chronic impairment, particularly radiotherapy. Chemotherapy has emerged as a promising therapy, although definitive findings are awaited. Breakthroughs in molecular biology have improved our understanding of tumours and have led to the development of novel treatments and better prognoses. Ongoing clinical trials will help to elucidate the optimum management of patients with LGG.

Molecular genetics of oligodendrogliomas: a model for improved clinical management in the field of neurooncology

Over the last several years, oligodendroglial tumors have become a model for the positive role of molecular genetics in improved treatment of patients with brain tumors. Oligodendrogliomas, in contrast to astrocytic gliomas, frequently respond to chemotherapy and have a better overall prognosis. Combined loss of chromosomes 1p and 19q has proven to be a powerful predictor of chemotherapeutic response and survival in oligodendrogliomas. In contrast, other genetic alterations, such as TP53 and PTEN mutations, EGFR amplification, and homozygous deletion of CDKN2A have been correlated with worse outcome in these tumors. Furthermore, 1p/19q loss has been shown to correlate with unequivocal oligodendroglial tumor histology, location and growth pattern of tumors within the brain, and magnetic resonance imaging characteristics. Although much is also known about the molecular pathological characteristics of astrocytic gliomas, the significance of this information to clinical management in patients with these tumors has not been as striking as has been the case for oligodendrogliomas; possible reasons for this are discussed. In this paper the author will summarize these advances, thus attempting to highlight the molecular genetic study of oligodendrogliomas as a model for improved clinical management in the field of neurooncology.

Chromosome 1p loss: a favorable prognostic factor in low-grade gliomas

Search for loss of heterozygosity on chromosomes 1p, 9p, 10q, and 19q, epidermal growth factor receptor (EGFR) gene amplification, and p53 expression was performed in a series of 131 low-grade gliomas. The profile of molecular changes, clinical findings, and histology were subsequently correlated with the course of the disease, mainly progression-free survival. When these parameters were considered as candidate variables in a multivariate analysis, only loss of heterozygosity on chromosome 1p was associated with increased progression-free survival (hazard ratio, 0.521), indicating a major favorable prognostic role of this genetic alteration in low-grade gliomas.

Optimal role of temozolomide in the treatment of malignant gliomas

Temozolomide (TMZ) is an alkylating agent that was approved for anaplastic astrocytoma and glioblastoma. Its role in the treatment of recurrent disease has been confirmed, and more importantly, alternative treatment schedules and combination regimens have been developed. A recent phase III trial has demonstrated a survival advantage for concomitant TMZ administration with radiotherapy in patients with newly diagnosed glioblastoma. Molecular studies suggest a strong predictive role of the DNA repair enzyme O6-methyl-guanine-DNA-methyl-transferase (MGMT) and outcome of TMZ-based chemotherapy. This review summarizes the current knowledge, highlights approved and nonapproved indications, and describes molecular studies that may allow us to identify the patients most likely to benefit from this treatment.

Long-term efficacy of early versus delayed radiotherapy for low-grade astrocytoma and oligodendroglioma in adults: the EORTC 22845 randomised trial

BACKGROUND

Postoperative policies of "wait-and-see" and radiotherapy for low-grade glioma are poorly defined. A trial in the mid 1980s established the radiation dose. In 1986 the EORTC Radiotherapy and Brain Tumor Groups initiated a prospective trial to compare early radiotherapy with delayed radiotherapy. An interim analysis has been reported. We now present the long-term results.

METHODS

After surgery, patients from 24 centres across Europe were randomly assigned to either early radiotherapy of 54 Gy in fractions of 1.8 Gy or deferred radiotherapy until the time of progression (control group). Patients with low-grade astrocytoma, oligodendroglioma, mixed oligoastrocytoma, and incompletely resected pilocytic astrocytoma, with a WHO performance status 0-2 were eligible. Analysis was by intention to treat, and primary endpoints were overall and progression-free survival.

FINDINGS

157 patients were assigned early radiotherapy, and 157 control. Median progression-free survival was 5.3 years in the early radiotherapy group and 3.4 years in the control group (hazard ratio 0.59, 95% CI 0.45-0.77; p<0.0001). However, overall survival was similar between groups: median survival in the radiotherapy group was 7.4 years compared with 7.2 years in the control group (hazard ratio 0.97, 95% CI 0.71-1.34; p=0.872). In the control group, 65% of patients received radiotherapy at progression. At 1 year, seizures were better controlled in the early radiotherapy group.

INTERPRETATION

Early radiotherapy after surgery lengthens the period without progression but does not affect overall survival. Because quality of life was not studied, it is not known whether time to progression reflects clinical deterioration. Radiotherapy could be deferred for patients with low-grade glioma who are in a good condition, provided they are carefully monitored.

Biologie moléculaire des tumeurs oligodendrogliales

Oligodendrogliomas have been the focus of considerable interest over the last decade, ever since they were recognized as chemosensitive tumors. However, the histological diagnosis remains highly controversial and unsatisfactory. Meanwhile, our understanding of glioma oncogenesis improved greatly. Gliomas are the consequence of specific genetic or epigenetic alterations - activations of oncogenes and inactivation of tumor suppressor genes - resulting in the disruption of critical cellular pathways and leading to phenotypic changes. Such genetic information complements the existing WHO morphological classification and, more importantly, provides additional prognostic markers. Indeed, 1p/19q deletion has been correlated with chemosensitivity in oligodendrogliomas, and is becoming more and more widely used in clinical practice. There is little doubt that emerging techniques, such as CGH-array and gene profiling will be very helpful in clinical practice for refining both classification and therapeutic indications of oligodendroglial tumors.

Place de la chimiothérapie et de la radiothérapie dans le traitement des oligodendrogliomes

Twenty years ago, the discovery of the chemosensitivity of anaplastic oligodendrogliomas considerably boosted interest for these tumors. In spite of difficulties for histological diagnosis, numerous studies on radiotherapy and chemotherapy for oligodendrogliomas appeared these last years. They allowed to detail the appropriate role for these therapeutics. For low grade oligodendrogliomas, radiotherapy delays the anaplastic transformation, but does not modify the overall survival; its indication has to be discussed particularly in the absence of clinical symptoms. Chemotherapy seems to be effective for low grade oligodendrogliomas as well as anaplastic tumors. However, phase III studies are necessary to clarify the contribution of chemotherapy for the treatment of low grade oligodendrogliomas, mainly in relation to radiotherapy. In anaplastic oligodendrogliomas, in spite of the lack of phase III studies, radiotherapy seems to be effective. Chemotherapy is clearly effective, but the most appropriate timing (neoadjuvant, adjuvant, at recurrence) is unknown. Results of current prospective studies are awaited. Recently, molecular genetic analysis, particularly the loss of 1p and 19q chromosomes appears to demonstrate a genetic influence on both prognosis and response to treatment.

Imaging in neurooncology

Imaging in patients with brain tumors aims toward the determination of the localization, extend, type, and malignancy of the tumor. Imaging is being used for primary diagnosis, planning of treatment including placement of stereotaxic biopsy, resection, radiation, guided application of experimental therapeutics, and delineation of tumor from functionally important neuronal tissue. After treatment, imaging is being used to quantify the treatment response and the extent of residual tumor. At follow-up, imaging helps to determine tumor progression and to differentiate recurrent tumor growth from treatment-induced tissue changes, such as radiation necrosis. A variety of complementary imaging methods are currently being used to obtain all the information necessary to achieve the above mentioned goals. Computed tomography and magnetic resonance imaging (MRI) reveal mostly anatomical information on the tumor, whereas magnetic resonance spectroscopy and positron emission tomography (PET) give important information on the metabolic state and molecular events within the tumor. Functional MRI and functional PET, in combination with electrophysiological methods like transcranial magnetic stimulation, are being used to delineate functionally important neuronal tissue, which has to be preserved from treatment-induced damage, as well as to gather information on tumor-induced brain plasticity. In addition, optical imaging devices have been implemented in the past few years for the development of new therapeutics, especially in experimental glioma models. In summary, imaging in patients with brain tumors plays a central role in the management of the disease and in the development of improved imaging-guided therapies.

A novel intramedullary spinal cord tumor model: functional, radiological, and histopathological characterization

OBJECT

Survival rates for high-grade intramedullary spinal cord tumors (IMSCTs) are approximately 30%, and optimal therapy has yet to be determined. Development of a satisfactory intramedullary tumor model is necessary for testing new therapeutic paradigms that may prolong survival. The authors report the technique, functional progression, radiological appearance, and histopathological features of a novel intramedullary model in rabbits.

METHODS

Ten New Zealand white rabbits were randomized to receive an intramedullary injection of either 25 microl of VX2 carcinoma cells (500,000 cells; six rabbits) or 25 microl of medium (Dulbecco modified Eagle medium; four rabbits) into the midthoracic spinal cord. Postoperatively the rabbits were evaluated twice daily for neurological deficits. High-resolution magnetic resonance (MR) images were acquired preoperatively and weekly postoperatively until onset of paraparesis, at which point the animals were killed, and the midthoracic spines were processed for histopathological examination. The VX2-carcinoma cells grew in 100% of animals injected and resulted in a statistically significant mean onset of paraparesis of 16.8 +/- 1.7 days (p = 0.0035, log-rank test), compared with animals in the control group in which neurological deficits were absent by Day 45. Contrast-enhanced T1-weighted MR imaging best demonstrated space-occupying intramedullary lesions and histopathological findings confirmed the intramedullary location of the tumor. Animals in the control group exhibited no functional, radiographic, or pathological signs of tumor.

CONCLUSIONS

Progression to paraparesis was consistent in all the VX2-injected animals, with predictable onset of paraparesis occurring approximately 17 days postinjection. Histopathological and radiological characteristics of the VX2 intramedullary tumor are comparable with those of aggressive primary human IMSCTs. Establishment of this novel animal tumor model will facilitate the testing of new therapeutic paradigms for the treatment of IMSCTs.

Treatment of medical complications in patients with brain tumors

Patients with primary brain tumors and those with cerebral metastases are at risk throughout their illness for several major medical problems, including vasogenic edema, seizures, and symptomatic venous thrombosis. In turn, the corticosteroids, anti-epileptic drugs, and anticoagulants used to treat these problems may produce significant adverse effects and result in important drug-drug interactions that may complicate chemotherapy. Although few Class I studies address any of these issues, guidelines can be offered to maximize quality of life and minimize hospital readmissions. Optimal management of brain edema involves minimizing corticosteroid use and tapering the steroid dose slowly to avoid steroid withdrawal symptoms. Prophylaxis of Pneumocystis pneumonia is necessary for patients requiring corticosteroids for more than 1 month. Anti-epileptic drugs (AEDs) should be avoided unless patients experience seizures. If possible, non-CTY (P450) enzyme-inducing drugs should be chosen. AED levels should be obtained frequently during corticosteroid taper. Multimodality venous thrombosis prophylaxis should begin at the time of the original surgery with external leg compression and unfractionated subcutaneous heparin or a low molecular weight heparin (LMWH). Brain tumor patients with symptomatic venous thrombosis or pulmonary embolism can be anticoagulated safely with warfarin or with LMWH, and LMWHs are preferable from the standpoints of efficacy, safety, and convenience for long-term outpatient treatment of venous thrombosis. Clinicians should be aware of potential drug-drug interactions between prescribed AEDs and chemotherapy and possible interactions with complementary and alternative therapies chosen by their patients. They also should be aware of interventions to minimize late sequelae of brain tumors and their treatment, including cognitive decline, depression, and increased stroke risk.

Oligodendroglioma

Surgery, radiotherapy, and chemotherapy are the standard treatment modalities for all primary brain tumors. Oligodendroglial tumors are uncommon primary brain tumors that typically are classified as low-grade or anaplastic based on their histologic appearance. A great deal of controversy has surrounded the diagnosis of an oligodendroglioma because no unique immunohistochemical marker exists to diagnose this tumor, forcing pathologists to render a diagnosis based on subjective microscopic features. Although once considered relatively rare, oligodendroglial tumors have been increasing in incidence because pathologists have become less rigorous about this diagnosis. However, recent advances in our understanding of the molecular genetic changes associated with brain tumors have identified loss of heterozygosity of chromosomes 1p and 19q as a unique genetic signature of most oligodendroglial tumors, an advance that has paved the way for pathologists to use molecular diagnostics to identify these tumors with improved reliability. These genetic derangements have significant clinical and therapeutic implications because they have been associated with a predictable and durable response to treatment, particularly chemotherapy, and an improved prognosis. The unique chemosensitivity of oligodendroglial tumors has been recognized by neurooncologists for at least 15 years, and various chemotherapeutic agents have been used to manage these diseases. However, the appropriate timing of chemotherapy, and the drugs of choice remain controversial. Increasingly, neurooncologists are reluctant to use radiotherapy as initial management for these diseases because of concerns surrounding the late neurocognitive sequelae of cranial irradiation. These toxicities are particularly important for patients with low-grade oligodendrogliomas in whom the prognosis often exceeds 10 years. Consequently, with the accumulating evidence supporting the chemosensitivity of low-grade and anaplastic oligodendrogliomas and the recent ability to use molecular diagnostics to identify a chemosensitive subset of oligodendrogliomas, neurooncologists are increasingly administering chemotherapy as the initial intervention for all oligodendroglial tumors that harbor favorable genetic derangements. Additionally, although immediate postoperative treatment is uniformly administered to patients with anaplastic oligodendrogliomas, there has been an increasing tendency to defer definitive therapy for those with low-grade oligodendrogliomas until evidence of progression. The development of temozolomide, an oral and well-tolerated alkylating agent that has activity against oligodendroglial tumors, has accelerated this trend to the extent that currently many patients with newly diagnosed low-grade and anaplastic oligodendrogliomas are offered this drug as initial treatment. This paper reviews the current management of oligodendrogliomas, with an emphasis on the expanding role of chemotherapy for these neoplasms.

Molecular changes in gliomas

PURPOSE OF REVIEW

Despite optimal clinical treatment, the prognosis for gliomas remains poor, and little progress has been observed during the last few years. Meanwhile, understanding of glioma oncogenesis has improved greatly. This review focuses on recent advances in molecular biology of glial tumors, with particular emphasis on lineage markers, genetic mechanisms underlying tumor progression, new diagnostic and prognostic markers, and potential therapeutic targets.

RECENT FINDINGS

The question of the cell of origin, illustrated by the evidence of tumor-derived multipotent progenitors, by the animal models of gliomas, and by lineage markers such as Olig1/2 markers, remains unsolved. Genotype/phenotype correlation studies have identified early and late genetic alterations related either to astrocytic or oligodendroglial phenotype. They complement the existing World Health Organization morphologic classification and provide additional prognostic markers such as 1p/19q deletion in oligodendrogliomas. Most of these genetic alterations result in the disruption of three main cellular systems: RB1, P53, and tyrosine kinase receptor pathways. New gene alterations have also been identified in glioma, promoting mitotic signal transduction, cell cycle regulation, apoptosis, angiogenesis, or invasion. Gene and protein profiling has been correlated with outcome.

SUMMARY

Management of gliomas, especially oligodendrogliomas with 1p19q deletion, benefits from advances in molecular genetics. A better understanding of the molecular pathogenesis and cellular lineage of gliomas will improve tumor classification and define more reliable prognostic markers. There is a hope that it will also lead to novel targets for therapy.

Correlations between molecular profile and radiologic pattern in oligodendroglial tumors

Objective: To investigate possible correlations between tumor location and genetic alterations in a series of oligodendrogliomas.

Methods: A series of 158 consecutive oligodendrogliomas were retrospectively reviewed. In each case, the radiologic picture and the chromosome 1p (chr 1p) status of the tumor detected by the loss of heterozygosity technique were analyzed. Correlation between tumor location and molecular profile was made by χ2 tests.

Results: Eighty-eight of the 158 patients had low-grade oligodendrogliomas, and 70 had anaplastic oligodendrogliomas. Overall, oligodendrogliomas with chr 1p loss were located preferentially in the anterior part of the brain, whereas tumors with intact chr 1p affected mainly the posterior part of the brain (p = 0.0038). In terms of lobar involvement, a preferential location of oligodendrogliomas with chr 1p loss was found in the frontal lobes as compared with the temporal, parietal, and occipital tumors (p < 0.01).

Conclusion: There is a significant correlation between loss of heterozygosity on chromosome 1p and tumor location in oligodendrogliomas, suggesting that subtypes of oligodendrogliomas could derive from site-specific precursors.

Stratégies et perspectives thérapeutiques des gliomes

The prognosis and the treatment of gliomas depend on age, performance status and histological grade. Symptomatic treatment relies on steroids against cerebral edema, anti-epileptic drugs for seizures and perioperatively, prevention of thrombo-embolism and digestive complications, physiotherapy. Specific therapies include surgery, radiotherapy and chemotherapy. Surgery is necessary for histological diagnosis. In low grade gliomas, it has a significant impact in terms of survival. In malignant gliomas, surgery provides symptomic relief without clearly improving survival. Radiation therapy has been shown to improve survival in malignant glioma, but not in asymptomatic low grade tumors. Chemotherapy has a modest efficacy in glioblastomas, whereas oligodendrogliomas with 1p 19q deletion are chemosensitive tumors.