About Glioma

Please note that this is general information only, and does not replace any advice you may receive from your Doctor.

What is glioma? What are the risk factors for glioma? Is glioma genetic? What are the symptoms and how is glioma diagnosed? How is glioma treated? Where do I get more information? References

What is glioma?

Glioma is the most common type of primary brain tumour in adults^1,2. Secondary brain tumours are cancers that have metastasized (spread) from elsewhere in the body.

Gliomas develop from glial cells, which are the supportive cells in the brain that help the neurons "do their job."¹

Types of glial cells include astrocytes, oligodendrocytes and ependymal cells, hence the tumours arising from these are known as astrocytomas, oligodendrogliomas and ependymomas respectively. Oligoastrocytomas are mixed tumours containing both astrocytes and oligodendrocytes.¹

Pathologists examine gliomas under the microscope to determine their grade, which is generally based on the World Health Organisation (WHO) classification system³:

• Low grade gliomas are benign, and include Grade 1 or Grade 2 tumours.
• High grade gliomas are malignant and include Grade 3 tumours:
  • Anaplastic astrocytoma
  • Anaplastic oligodendroglioma
  • Anaplastic oligoastrocytoma
  and Grade 4:
  • Glioblastoma multiforme (GBM).

What are the risk factors for glioma?

Very little is known about what causes glioma. The only validated risk factors are:

1. Age
2. Sex
3. Irradiation to the head

Age

The median age of onset is about 45 years of age for Grade 3 and 60 years for Grade 4⁴.

Sex

Incidence and mortality is consistently higher in males¹.

Irradiation to the head

This is sometimes administered during previous treatment for cancer and can increase the risk of developing glioma 10 or 20 years later⁶.

There is no evidence to support increased risk due to mobile phone use or cigarette smoking. The role of other environmental factors, and occupation, is unclear^5,7.

Is glioma genetic?

Only 5% of all glioma cases can be accounted for by a family history of high grade or low grade glioma⁸.

Some studies have shown an association between certain genes (eg those involved in repairing DNA) and tumour behaviour^4,9-12.

By bringing together a wide range of data on potentially all glioma patients in Australia, AGOG is in a very good position to validate these findings and look for new genetic causes and risk factors¹³.

What are the symptoms and how is glioma diagnosed?

Glioma involves the abnormal growth of glial cells, which are spread throughout the brain. Therefore a glioma can potentially interfere with all normal brain functions, depending on the exact size and location of the tumour¹.

Common symptoms include: headache, seizure, weakness or sensory loss, confusion, visual disturbance or personality change¹.

Diagnosis is based on Magnetic Resonance Scanning (MRI), surgical biopsy and examination by a pathologist specializing in brain diseases¹.

How is glioma treated?

There is currently no cure for glioma. Tumour behaviour does vary markedly between patients and between tumour types, however prognosis is generally poor. Median survival is 3-5 years for Grade 3 and less than 1 year for Grade 4 disease⁴.

Treatment usually involves a multi-disciplinary approach by a team of doctors with different specialties, all aiming to relieve symptoms, prolong survival and improving quality of life.

The standard of care in Australia is surgery to remove the tumour (if assessed as safe by the surgeon), followed by combined chemoradiotherapy then 6 months of further chemotherapy using temozolomide¹⁴.

Where do I get more information?

The Cancer Council NSW
www.cancercouncil.com.au/canceranswers/
Helpline: 13 11 20

National Cancer Institute (USA)
www.cancer.gov/cancertopics/types/brain/

The Brain Tumor Epidemiology Consortium (BTEC)
epi.grants.cancer.gov/btec/

References

1. National Cancer Institute, US Department of Health and Human Services, US National Institutes of Health, US. www.cancer.gov/cancertopics/types/brain/
2. CBTRUS (2004). Statistical Report: Primary Brain Tumours in the United States, 1997-2001. The Central Brain Tumor Registry of the United States. www.cbtrus.org/reports/2004-2005/2005report.pdf
3. Pathology and genetics of tumours of the nervous system (2000). In: World Health Organization Classification of Tumours of the Nervous System, Editorial and Consensus Conference Working Group. Kleihues P, Cavenee WK (Eds). IARC Press, Lyon, France.
4. Laws ER, Parney IF, Huang W, Anderson F, Morris AM, Asher A et al (2003). Survival following surgery and prognostic factors for recently diagnosed malignant glioma: data from the Glioma Outcomes Project. J Neurosurg 99: 467-473.
5. Holick CN, Giovannucci EL, Rosner B, Stampfer MJ, DS Michaud DS . Prospective study of cigarette smoking and adult glioma: Dosage, duration and latency. Neuro-oncol 9(3): 326-334.
6. Walter AW, Hancock ML, Pui CH, et al (1998). Secondary brain tumours in children treated for acute lymphoblastic leukemia at St Jude Children's Research Hospital. J Clin Oncol 16: 3761-7.
7. Inskip PD, Tarone RE, Hatch EE, Wilcosky TC, WR Shapiro WR, Selker RG, Fine HA, Black PM et al (2001). Cellular-Telephone Use and Brain Tumors. N Engl J Med 344(2): 79-86 (2001).
8. Bondy M, Wiencke J, Wrensch M, Kyritsis AP (1994). Genetics of primary brain tumours: a review. J Neurooncol 18: 69-81.
9. Simon M, Ludwig M, Fimmers R, Mahlberg R, Muller-Erkwoh A, Koster G, Schramm J (2006). Variant of the CHEK2 gene as a prognostic marker in glioblastoma multiforme. Neurosurgery 59(5): 1078-85.
10. Bhowmick DA, Zhuang Z, Wait SD, Weil RJ (2004). A functional polymorphism in the EFG gene is found with increased frequency in glioblastoma multiforme patients and is associated with more aggressive disease. Cancer Res 64: 1220-1223.
11. Oku MF, Selvan M, Wang LE et al (2004). Glutathione S-transferase polymorphisms and survival in primary malignany glioma. Clin Cancer Res 10: 2618-2625.
12. Tang J, Shao W, Dorak MT et al (2005). Positive and negative associations of human leukocyte antigen variants with the onset and prognosis of adult glioblastoma multiforme. Cancer Epid Biomarkers Prev 14: 2040-2044.
13. Chanock SJ, Manolio T, Boehnke M, Boerwinkle E, Hunter DJ, et al (2007). What constitutes replication of a genotype-phenotype association ? Nature 447(7145): 655-660.
14. Stupp R, Mason WP, van den Brent MJ, et al (2005). Radiotherapy plus concomitant and adjuvant temozolomide for newly diagnosed glioblastoma. N Engl J Med 352:987-96.