Low-grade gliomas: introduction and overview

A national perspective of adult gangliogliomas

Gangliogliomas (GG) are rare tumors of the nervous system. Patient characteristics and clinical outcomes of low and high-grade GG have been difficult to elucidate in the adult population. This study aims to further elaborate on GG treatment and overall survival utilizing a larger cohort than previously published. The USA National Cancer Database was utilized to evaluate adult (age 18years and older) patients diagnosed with GG between 2004 and 2006. Descriptive statistics and Kaplan-Meier overall survival estimates were provided. A total of 198 adult GG patients were diagnosed between 2004 and 2006. Of these, 181 (91.4%) were low-grade and 17 (8.6%) high-grade GG. Overall, the median age was 36years; approximately 50% of patients were female, and 86.5% Caucasian. Most patients (59%) had near/gross total resection. Radiation and chemotherapy were prescribed in 18 (9.1%) and 11 (5.7%) patients, respectively. Radiation (64.7% versus 3.9%, p<.0001) and chemotherapy (47.1% versus 1.7%, p<.0001) were more frequently given to patients with high-grade tumors than low-grade. The median overall survival of high-grade GG was 44.4months (95% confidence interval [CI]: 10.5-92.5) while the corresponding estimate for low-grade tumors was not reached. Older age (hazard ratio [HR] 1.72, 95% CI: 1.26-2.34) and high tumor grade (HR 3.91, 95% CI: 1.43-10.8) were found to be associated with poor survival. Adult GG have a temporal lobe predilection and overall gross total resection rate of 59%. Older patients with high-grade tumors had an increased hazard of mortality. High-grade GG were significantly more likely to be treated with radiation therapy and chemotherapy.

Perfusion Magnetic Resonance Imaging Predicts Patient Outcome as an Adjunct to Histopathology: A Second Reference Standard in the Surgical and Nonsurgical Treatment of Low-grade Gliomas

OBJECTIVE:

To determine whether relative cerebral blood volume (rCBV) can predict patient outcome, specifically tumor progression, in low-grade gliomas (LGGs) and thus provide a second reference standard in the surgical and postsurgical management of LGGs.

METHODS:

Thirty-five patients with histologically diagnosed LGGs (21 low-grade astrocytomas and 14 low-grade oligodendrogliomas and low-grade mixed oligoastrocytomas) were studied with dynamic susceptibility contrast-enhanced perfusion magnetic resonance imaging. Wilcoxon tests were used to compare patients in different response categories (complete response, stable, progressive, death) with respect to baseline rCBV. Log-rank tests were used to evaluate the association of rCBV with survival and time to progression. Kaplan-Meier time-to-progression curves were generated. Tumor volumes and CBV measurements were obtained at the initial examination and again at follow-up to determine the association of rCBV with tumor volume progression.

RESULTS:

Wilcoxon tests showed patients manifesting an adverse event (either death or progression) had significantly higher rCBV (P = 0.003) than did patients without adverse events (complete response or stable disease). Log-rank tests showed that rCBV exhibited a significant negative association with disease-free survival (P = 0.0015), such that low rCBV values were associated with longer time to progression. Kaplan-Meier curves demonstrated that lesions with rCBV less than 1.75 (n = 16) had a median time to progression of 4620 ± 433 days, and lesions with rCBV more than 1.75 (n = 19) had a median time to progression of 245 ± 62 days (P &lt; 0.005). Lesions with low baseline rCBV (&lt;1.75) demonstrated stable tumor volumes when followed up over time, and lesions with high baseline rCBV (&gt;1.75) demonstrated progressively increasing tumor volumes over time.

CONCLUSION:

Dynamic susceptibility contrast-enhanced perfusion magnetic resonance imaging may be used to identify LGGs that are either high-grade gliomas, misdiagnosed because of sampling error at pathological examination or that have undergone angiogenesis in the progression toward malignant transformation. This suggests that rCBV measurements may be used as a second reference standard to determine the surgical management/risk–benefit equation and postsurgical adjuvant therapy for LGGs.

Surgery for low-grade gliomas: current evidence and controversies

Despite decades of studies, the surgical management of cerebral low-grade gliomas remains quite controversial. Recommendations range from observation with biopsy to radical resection. This controversy arises from several factors, chief of which is the lack of prospective, randomized studies specifically addressing the issue of resection. Nevertheless, the available data, with its inherent inadequacies, must be used to help guide the care of these patients. This article reviews the current literature on the role of surgery for these tumors and attempts to put forward reasonable treatment options in an area where even the American Association of Neurological Surgeons can find no standard management to recommend aside from biopsy prior to the onset of therapy.

Angiogenesis in gliomas: imaging and experimental therapeutics

Much of the interest in angiogenesis and hypoxia has led to investigating diagnostic imaging methodologies and developing efficacious agents against angiogenesis in gliomas. In many ways, because of the cytostatic effects of these agents on tumor growth and tumor-associated endothelial cells, the effects of therapy are not immediately evident. Hence finding clinically applicable imaging tools and pathologic surrogate markers is an important step in translating glioma biology to therapeutics. There are a variety of strategies in the approach to experimental therapeutics that target the hypoxia-inducible factor pathway, the endogenous antiangiogenic and proangiogenic factors and their receptors, adhesion molecules, matrix proteases and cytokines, and the existing vasculature. We discuss the rationale for antiangiogenesis as a treatment strategy, the preclinical and clinical assessment of antiangiogenic interventions and finally focus on the various treatment strategies, including combining antiangiogenic drugs with radiation and chemotherapy.

Low-grade gliomas: dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging--prediction of patient clinical response

PURPOSE

To determine retrospectively whether relative cerebral blood volume (CBV) measurements can be used to predict clinical response in patients with low-grade gliomas.

MATERIALS AND METHODS

Approval for this retrospective HIPAA-compliant study was obtained from the Institutional Board of Research Associates, with waiver of informed consent. Thirty-five patients (23 male and 12 female patients; median age, 39 years; range, 4-80 years) with histologically diagnosed low-grade gliomas (21 low-grade astrocytomas and 14 low-grade oligodendrogliomas and low-grade mixed oligoastrocytomas) were examined with dynamic susceptibility-weighted contrast material-enhanced perfusion magnetic resonance (MR) imaging. Wilcoxon tests were used to compare patients in different response categories (complete response, stable, progressive, death) with respect to baseline relative CBV. Kaplan-Meier survival curves, log-rank tests, and Weibull survival models were used to characterize and evaluate the association of baseline relative CBV with time to progression. Tumor volumes and relative CBV measurements were obtained at initial examination and follow-up.

RESULTS

Lesions with relative CBV less than 1.75 had a median time to progression of 4620 days +/- 433 (standard deviation), and lesions with relative CBV more than 1.75 had a median time to progression of 245 days +/- 62. Patients who had an adverse event (either death or progression) had significantly higher (P = .003) relative CBV than did patients without adverse events (either complete response or stable disease). Lesions with low baseline relative CBV had stable tumor volumes at follow-up over time, whereas those with high baseline relative CBV (>1.75) had progressively increasing tumor volumes over time.

CONCLUSION

Dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging can help to identify low-grade gliomas that will progress rapidly and a subset of low-grade gliomas that have a propensity for malignant transformation.

The spectrum of long-term epilepsy-associated tumors: long-term seizure and tumor outcome and neurosurgical aspects

PURPOSE

To describe the histologic spectrum and clinical characteristics of patients with neuroepithelial tumors and drug-resistant epilepsy and to analyze clinical data and treatment related to seizure outcome and survival.

METHODS

Data were analyzed from 207 consecutive patients with intractable epilepsy (aged 2-54 years), who between 1988 and 1999 had >or=50% resection of supratentorial, neuroepithelial tumors. Extent of resection was assessed on postoperative magnetic resonance imaging (MRI); seizure outcome was classified according to Engel's outcome scale; and follow-up data were prospectively updated.

RESULTS

Median follow-up was eight years (range, 2-14 years). Histologic examination revealed 154 classic epilepsy-associated tumors (ganglioglioma, dysembryoplastic neuroepithelial tumor, pleomorphic xanthoastrocytoma, and pilocytic astrocytomas) and 53 others (astrocytomas and oligodendrogliomas). Four World Health Organization (WHO) grade III tumors were found (astrocytoma, n = 3; ganglioglioma, n = 1). After surgery, 82% of the patients were seizure free (class I). The following factors were associated with improved seizure outcome: Short duration of epilepsy before surgery, single EEG focus, absence of additional hippocampal sclerosis or cortical dysplasia, transsylvian approach, other than astrocytomas, and complete tumor resection. After 5 years, only nine (4%) patients had tumor recurrence, four (2%) with malignant transformation and death. None of the four patients with anaplastic tumors died. Even patients with astrocytomas of WHO grade II or III showed 10-year recurrence of only 25% and 10-year survival of 90%.

CONCLUSIONS

Tumors associated with long-term epilepsy should be removed early for two different reasons: high rate of seizure freedom and rare but potential risk of malignant tumor progression. The unexpected long survival of these astrocytomas should be investigated by using immunohistochemistry and molecular biology.

Telomerase as a therapeutic target for malignant gliomas

Telomerase, a ribonucleoprotein enzyme, is considered as a potential target of cancer therapy because of its preferential expression in tumors. In particular, malignant gliomas are one of the best candidates for telomerase-targeted therapy. It is because malignant gliomas are predominantly telomerase-positive, while normal brain tissues do not express telomerase. In theory, there are two telomerase-associated therapeutic approaches for telomerase-positive tumors. One approach is the anti-telomerase cancer therapy to directly inhibit telomerase activity, resulting in apoptotic cell death or growth arrest. Two major components of the telomerase holoenzyme complex, the RNA template (hTER) and catalytic subunit (reverse transcriptase, hTERT) are well considered as therapeutic targets. The other approach is the telomerase-specific cancer therapy by targeting telomerase-expressing tumor cells as a means to directly kill the cells. Strategies using the transfer of therapeutic gene under the hTERT promoter system as well as immunotherapy directed against telomerase-positive cells are generally included. These telomerase-associated therapies are very promising for the treatment of malignant gliomas.

The role of surgery in low grade gliomas

Several prognostic factors appear to be more important than treatment factors in determining the outcome of patients with low grade glioma. The role of surgery in establishing a histological diagnosis or in relieving neurological deficit is well established. The role of surgery in prolonging survival of patients with low grade glioma however, remains controversial, largely because studies in the literature on the management of this disease have been predominantly descriptive and observational, which precludes the setting of standards for the management of these patients. Several viable management options are discussed.

Complications and expected outcome of glioma surgery

The management of patients with intracerebral glioma is focused upon the selection of treatment modalities that prolong survival while minimizing the risk of complications and maintaining an adequate quality of life. In the author's experience, patients with low-grade gliomas are best treated with gross total resection in order to decrease the risk of recurrence with higher grade lesions. In patients with high-grade glioma, age, Karnofsky Performance Status, histology and the use of radiotherapy are major predictors of survival. The extent of surgical resection is less important than these factors, but recent series support a survival advantage in patients that undergo more extensive surgery. The major complication from surgical resection is neurologic impairment. Careful preoperative planning with the assistance of functional MRI and intraoperative mapping is useful for accomplishing the maximum safe resection.