Chapter 1 - Epidemiology, Pathogenesis and Risk Factors of Brain Tumours
High-dose ionising radiation is the only unequivocal environmental risk factor that was identified for glial and meningeal neoplasms. An association was observed in A-bomb studies, nuclear test fallout data, therapeutic radiation, and occupational and environmental studies.
In 2011, the International Agency for Research on Cancer classified mobile phone use and other radiofrequency electromagnetic fields as a possible carcinogenic agent (Group 2B).
Many environmental risk factors (non-ionising radiation, e.g. mobile phones, pesticides, solvents, etc.) have been examined as potential contributors to glioma risk, with inconclusive results until now.
A heritable genetic contribution to glioma genesis was initially suggested by the increased incidence of these tumours in families with Mendelian cancer syndromes.
But a very small portion of these tumours are caused by Mendelian disorders, including neurofibromatosis, tuberous sclerosis and Li-Fraumeni syndrome.
Excluding genetic syndromes, familial cases of primary CNS tumours represent less than 5% of cases.
Epidemiological studies consistently suggest that allergic conditions, including asthma, hay fever, eczema and food allergies, are associated with reduced glioma risk.
In the USA, incidences of glioblastoma and oligodendroglioma are approximately 2 times greater in white people than in black people, but the incidence of meningioma is higher in black people than white people.
Genome-wide association studies have identified heritable risk alleles within 7 genes that are associated with increased risk of glioma.
Revision Questions
- What is the only identified environmental risk factor that increases the risk of glioma or meningioma?
- What are the rare genetic syndromes associated with gliomas?
- Allergy is associated with a reduced risk of glioma. True or false?
