Oligodendroglioma: Difference between revisions

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==Treatment==
==Treatment==
[[Oligodendroglioma medical therapy|Medical therapy]] | [[Oligodendroglioma surgery|Surgical options]] | [[Oligodendroglioma primary prevention|Primary prevention]]  | [[Oligodendroglioma secondary prevention|Secondary prevention]] | [[Oligodendroglioma cost-effectiveness of therapy|Financial costs]] | [[Oligodendroglioma future or investigational therapies|Future therapies]]
[[Oligodendroglioma medical therapy|Medical therapy]] | [[Oligodendroglioma surgery|Surgical options]] | [[Oligodendroglioma primary prevention|Primary prevention]]  | [[Oligodendroglioma secondary prevention|Secondary prevention]] | [[Oligodendroglioma cost-effectiveness of therapy|Financial costs]] | [[Oligodendroglioma future or investigational therapies|Future therapies]]
==Histopathological Grading==
The histopathologic grading of oligodendrogliomas is controversial.  Currently the most commonly used grading schema is based on year 2007 [[World Health Organization]] (WHO) guidelines.  Oligodendrogliomas are generally dichotomized into grade II (low grade) and grade III (high grade) tumors.  The designation of grade III oligodendroglioma (high grade) generally subsumes the previous diagnoses of anaplastic or malignant oligodendroglioma. 
Unfortunately, the WHO guidelines include subjective criteria in differentiating grade II and grade III tumors including the appreciation of “significant” hypercellularity and pleomorphism in the higher grade lesion.  In addition, the presence of low mitotic activity, vascular proliferation and necrosis, including pseudopallisading necrosis are insufficient by themselves to elevate the grade of these tumors.  This leads to inevitable interobserver variability in diagnosis by pathologists.  The ultimate responsibility for making treatment decisions and interpretation of these diagnoses lies with the oncologist in consultation with the patient and their family.   
It has been proposed that [[World Health Organization|WHO]] guidelines should contain a category for grade IV oligodendrogliomas which essentially appear to be glial neoplasms with overwhelming features of [[glioblastoma multiforme]] (GBM) arising from known lower grade oligodendrogliomas or GBM with a significant proportion of oligodendroglial differentiation.  The diagnostic ultility of this latter category is uncertain as these tumors may behave either like glioblastoma or grade III oligodendrogliomas.  As such, this is an exceptionally unusual diagnosis. 
The updated WHO guidelines published in 2007 recommends classifying such tumors for the time being as ‘glioblastoma with oligodendroglioma component’. <ref>{{cite journal |author=Louis D, Ohgaki H, Wiestler O, 'et al'' |title=The 2007 WHO Classification of Tumours of the Central Nervous System |journal=Acta Neuropathologica |volume=114 |issue=2 |pages=97-109 |year=2007 |pmid=17618441 |doi=10.1007/s00401-007-0243-4}}</ref> It remains to be established whether or not these tumors carry a better prognosis than standard glioblastomas.


==Molecular genetics==
==Molecular genetics==

Revision as of 19:26, 17 January 2012

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Oligodendroglioma
ICD-10 C71
ICD-9 191.9
ICD-O: 9450/3-9451/3
DiseasesDB 29450
MeSH D009837

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [3]

Please Take Over This Page and Apply to be Editor-In-Chief for this topic: There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [4] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.

Overview

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Epidemiology & Demographics

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Causes

Differentiating Oligodendroglioma

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Molecular genetics

By far, the most common structural deformity found is co-deletion of chromosomal arms 1p and 19q. The high frequency of co-deletion (60-80%) is a striking feature of this glial tumour, and is considered as a "genetic signature" of oligodendroglioma. 1p/19q deletion has been correlated with both chemosensitivity and improved prognosis in oligodendrogliomas.[1][2] A t(1;19)(q10;p10) translocation mediates the combined deletions of 1p and 19q. The gene products lost as a consequence of this codeletion may include mediators of resistance to genotoxic therapies. Alternatively, 1p/19q loss might be an early oncogenic lesion promoting the formation of glial neoplasms, which retain high sensitivity to genotoxic stress.

Prognosis & treatment

Oligodendrogliomas are generally felt to be incurable using current treatments. However compared to the more common astrocytomas, they are slowly growing with prolonged survival. In one series, median survival times for oligodendrogliomas were 11.6 years for grade II and 3.5 years for grade III.[3] Because of the indolent nature of these tumors and the potential morbidity associated with neurosurgery, chemotherapy and radiation therapy, most neurooncologists will initially pursue a course of watchful waiting and treat patients symptomatically. Symptomatic treatment often includes the use of anticonvulsants for seizures and steroids for brain swelling. PCV chemotherapy (Procarbazine, CCNU and Vincristine) has been shown to be effective and is currently the most commonly used chemotherapy regimen used for treating anaplastic oligodendrogliomas.[4] Temozolomide is a common chemotheraputic drug to which oligodendrogliomas appear to be quite sensitive. It is often used as a first line therapy.

Because of their diffusely infiltrating nature, oligodendrogliomas cannot be completely resected and are not curable by surgical excision. If the tumor mass compresses adjacent brain structures, a neurosurgeon will typically remove as much of the tumor as he or she can without damaging other critical, healthy brain structures. Surgery may be followed up by chemotherapy, radiation, or a mix of both. Oligodendrogliomas, like all other infiltrating gliomas, have a very high (almost uniform) rate of recurrence and gradually increase in grade over time. Recurrent tumors are generally treated with more aggressive chemotherapy and radiation therapy. Recently, stereotactic surgery has proven successful in treating small tumors that have been diagnosed early.

Long-term survival is reported in a minority of patients.[5] With aggressive treatment and close monitoring, it is possible to outlive the typical life expectancies for both low grade and high grade oligodendrogliomas. In rare cases, patients have survived for up to fifteen years post-diagnosis. Westergaard’s study (1997) showed that patients younger than 20 years had a median survival of 17.5 years.[6] Another study shows a 34% survival rate after 20 years. [7]

References

  1. Laigle-Donadey F, Benouaich-Amiel A, Hoang-Xuan K, Sanson M (2005). "[Molecular biology of oligodendroglial tumors]". Neuro-Chirurgie (in French). 51 (3-4 Pt 2): 260–8. PMID 16292170.
  2. Walker C, Haylock B, Husband D; et al. (2006). "Clinical use of genotype to predict chemosensitivity in oligodendroglial tumors". Neurology. 66 (11): 1661–7. doi:10.1212/01.wnl.0000218270.12495.9a. PMID 16769937.
  3. Ohgaki H, Kleihues P. Population-based studies on incidence, survival rates, and genetic alterations in astrocytic and oligodendroglial gliomas. J Neuropathol Exp Neurol. 2005 Jun;64(6):479-89. PMID: 15977639
  4. Herbert H. Engelhard, M.D., Ph.D., Ana Stelea, M.D., and Arno Mundt, M.D.[1] p.452
  5. Tatter SB. Recurrent malignant glioma in adults. Curr Treat Options Oncol. 2002 Dec;3(6):509-24. PMID: 12392640,
  6. Herbert H. Engelhard, M.D., Ph.D., Ana Stelea, M.D., and Arno Mundt, M.D.[2] p.449
  7. Feigenberg SJ, Amdur RJ, Morris CG, Mendenhall WM, Marcus RB, Friedman WA (2003). "Oligodendroglioma: does deferring treatment compromise outcome?". Am. J. Clin. Oncol. 26 (3): e60–6. doi:10.1097/01.COC.0000072507.25834.D6. PMID 12796617.

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