Prognostic significance of the endothelial surface in low-grade resected oligodendrogliomas

Assessment of tumor angiogenesis as a prognostic factor of survival in patients with oligodendroglioma

According to World Health Organization (WHO) and Daumas-Duport grading systems, progression of oligodendrogliomas (ODGs) to a higher grade (WHO grade III, grade B) is associated with increased angiogenesis. Based on multivariate assessment of molecular, pathological, and radiological parameters, we further assessed the influence of tumor angiogenesis on tumor progression and patient survival. Patients with a diagnosis of ODG, consecutively treated in a single institution, were reviewed and reclassified according to WHO and Daumas-Duport grading systems. MRI scans were reviewed to assess contrast enhancement and necrosis. Tissue sections were used for pathology review and to evaluate immunostaining of vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor (VEGF-R), Ki-67, and CD34. Multivariate analysis was performed to assess the impact of tumor angiogenesis-related pathological and radiological factors on patient survival. One hundred thirty-four patients with pure ODG were included in this study. Multivariate analysis identified four independent poor prognostic factors: necrosis, absence of seizure, increased vascularization, and age >55 years. A subgroup of patients with tumor necrosis, increased vascularization, and absence of seizures had a significantly worse outcome than predicted, with a median overall survival of 14.2 months. VEGF expression was significantly higher in this subgroup and correlated with disease progression regardless of histologic grade. Based on the presence of radiological or pathological necrosis, contrast enhancement or endothelial hyperplasia, and absence of seizures, a high risk group of ODG can be identified with significantly worse overall survival. Also, VEGF over-expression in ODG constitutes an early marker for predicting tumor progression.

CXCL12 expression is predictive of a shorter time to tumor progression in low-grade glioma: a single-institution study in 50 patients

The clinical course of 50 patients with low-grade glioma (31 male, 19 female) undergoing surgery at a single Institution from 1992 to 1996 was analyzed in relationship with known prognostic factors as far as time to tumor progression (TTP) and survival time (ST) are concerned. Moreover, microvessel density (MVD) and expression of the angiogenesis-related chemokine CXCL12 were investigated in surgical specimens. Age at diagnosis ranged from 1 to 68 years (median 30). Histology revealed 11 fibrillary, 6 protoplasmatic, 5 gemistocytic astrocytoma, 18 oligoastrocytoma and 10 oligodendroglioma. Mean follow-up was 86 months. Four patients were lost to follow-up. Of the remaining 46, twenty-four have shown disease progression and 14 have died. Median overall survival was not achieved; an estimated 75% percentage of survivors was found at 78 months. Complete gross tumor removal was associated to a longer TTP (P = 0.04 logrank). Of the investigated immunohistochemical parameters, while MVD was not predictive of subsequent TTP, expression of CXCL12 was associated with a significantly shorter TTP (P = 0.01 logrank): this predictive value remained significant (P = 0.02) at multivariate analysis. The data suggest the possible prognostic value for CXCL-12 (an angiogenesis- and tumor-growth-related chemokine) on TTP in low-grade gliomas.

Histologic measures of angiogenesis in human primary brain tumors

Quantitative determination of the degree of vascularity has been shown to be independently prognostically significant in many human tumor types. In particular, tumor vascularity has known importance in astrocytomas, in which endothelial proliferation is a criterion for anaplasia in many grading schemes. This chapter summarizes the known associations of quantitated microvessel parameters obtained from histologic sections of human brain tumors with clinical outcome, or other pathobiologic factors that have been examined. Among the conclusions are 1) brain tumors have the unique feature of complex "glomeruloid" vessels, as well as heterogeneity of microvascular distribution and caliber; 2) lower-grade astrocytomas incorporate pre-existing vessels, while glioblastomas develop new vessels; 3) quantitation may have additional independent prognostic value over and above routine histologic grade in low-grade astrocytomas with low tumor cell proliferative indices. These findings have implications for the appropriateness of antiangiogenic therapies

Oligodendroglioma and anaplastic oligodendroglioma:

BACKGROUND

Recent advances that have been made in diagnostic imaging, surgical technique, chemotherapy, molecular biology, and prediction of therapeutic response could have potential impact on the optimal diagnosis and treatment of patients with brain tumors, especially those with oligodendrogliomas. In this article, the topic of oligodendroglioma and anaplastic oligodendroglioma is reviewed, highlighting the new clinical developments.

METHODS

Information for this review was obtained by performing a Medline search for recent references using the term "oligodendroglioma." The bibliographies of papers obtained also were checked for articles that could provide additional understanding of this disease and its current treatment.

RESULTS

The incidence of oligodendroglioma is increasing, most likely due to its improved recognition. Seizures and/or headaches are still common presenting features, and surgery continues to be the primary treatment. Positron emission tomography (PET) and molecular analysis of the surgical specimen are emerging as important diagnostic tools. Patients having either oligodendroglioma or anaplastic oligodendroglioma are likely to respond to chemotherapy. This has had an impact upon the timing of radiation therapy. Survival times are increasing, and patients can now be divided into prognostic subgroups based on the molecular features of their tumors. While procarbazine-CCNU-vincristine (PCV) chemotherapy has been the standard, other agents, notably temozolomide, are currently being tested.

CONCLUSIONS

The algorithm for diagnosing and treating patients with oligodendrogliomas has changed. Neurosurgeons need to be aware of the new developments so they can offer sound advice to their patients.

Dynamic susceptibility contrast MRI of gliomas

Dynamic susceptibility contrast imaging has proven to be useful in brain tumor studies, and it provides additional information on tumor characteristics based on the microvascular structure of gliomas. The cerebral blood volume maps can be used to noninvasively grade gliomas, to determine optimal biopsy sites, to separate radiation necrosis from tumor regrowth, and to plan and follow irradiation, chemo- and antiangiogenic therapy. Besides of cerebral blood volume mapping, dynamic susceptibility contrast imaging sets also contain information about the flow and permeability properties of the tumor microvascular system. When combined with the conventional MRI, dynamic susceptibility contrast techniques offer important functional information about the biology of gliomas in a cost-effective way.

Immunohistochemical markers for prognosis of oligodendroglial neoplasms

Despite numerous previous studies, oligodendrogliomas continue to generate considerable controversy in the identification of prognostic factors, including single histopathological patterns, and grade of tumor malignancy. The prognostic significance of various pathological and immunohistochemical factors has been intensively examined but numerous studies have yielded conflicting results. In the present study, biopsy samples of 123 oligodendrogliomas were examined immunohistochemically to evaluate a possible association between expression of various tumor-associated antigens and clinical outcome. Both the progression-free and overall survival times were significantly reduced for high-grade tumors, for Ki-S1 labeling index (LI) > 10%, for p27 LI < 20% and for p18, p53, and vascular endothelial growth factor (VEGF)-positive tumors. For low-grade tumors survival rates were significantly reduced for p27 LI less than 20%, whereas high-grade oligodendrogliomas with Ki-S1 LI greater than 10%, and with p18 positivity revealed significantly shortened survival times. We found no differences in survival times in patients with or without p 14ARF, p21, mdm2, and pRb immunoreactivity. Multivariate analysis revealed that risk of oligodendroglioma progression is associated with high-grade tumors, with Ki-S1 LI > 10%, and with p27 LI < 20%; whereas risk of death is associated with high-grade tumors, with Ki-S1 LI > 10%, and with p18 positivity. CART modeling process identified four final groups of oligodendroglioma patients: (1) thirty-nine patients with low-grade tumors and p27 LI > 20%; (2) twenty patients with low-grade tumors and p27 LI < 20%; (3) thirty-four patients with high-grade tumors and Ki-S1 LI < 10%; and (4) thirty patients with high-grade tumors and Ki-S1 LI >10%. In summary, both the p27 and Ki-S1 scores were found to be the strong predictors of oligodendroglioma outcome together with the WHO tumor grade and they seem to be useful for assessing individual prognosis in routinely processed specimens.