Brain Cancer
Brain cancers are sometimes seen as difficult to treat because of their location, and proximity to delicate structures. These tumours develop a complex microenvironment of cancer cells, immune system cells (microglial cells, macrophages, and lymphocytes), and endothelial cells, which can contribute to drug resistance in treatments. The immune system cells are normally involved in surveillance and defence against infections and cancer cells, and they can make up 30-50% of a brain tumour mass (Wu & Watabe, 2017).
Microglia, the immune system macrophage cells in the central nervous system, normally contribute to clearance of infections and cancer cells. However in prolonged chronic inflammatory conditions, the continued activation of microglia can cause them to release pro-tumour chemicals which results in oxidative stress and inflammation which can contribute to neurodegenerative diseases and brain cancers (Wu & Watabe, 2017).
Cancer stem cells are frequently found in brain tumours. These stem cells have the ability to become resistant to some treatments and can evade the immune system. This can lead to tumour growth and recurrent tumours (Abou-Antoun, Hale, Lathia & Dombrowski, 2017).
Brain tumours in childhood differ from those in adulthood in several ways. In childhood, brain tumours are more a result of genetic and epigenetic factors (ie, how the environment causes genetic changes). In adults, there can be epigenetic factors involved, but brain tumours result more from long-term carcinogen exposure causing genetic damage and mutations leading to cancer (Abou-Antoun, Hale, Lathia & Dombrowski, 2017).
There are more than 40 types of brain tumours, which are grouped into two main types (Cancer Council Australia, 2017):
Symptoms of brain cancer can vary depending on the location of the tumour, and include the following (Cancer Council Australia, 2017):
The risk factors of brain cancer include the following (Osiecki, 2012, p334):
Microglia, the immune system macrophage cells in the central nervous system, normally contribute to clearance of infections and cancer cells. However in prolonged chronic inflammatory conditions, the continued activation of microglia can cause them to release pro-tumour chemicals which results in oxidative stress and inflammation which can contribute to neurodegenerative diseases and brain cancers (Wu & Watabe, 2017).
Cancer stem cells are frequently found in brain tumours. These stem cells have the ability to become resistant to some treatments and can evade the immune system. This can lead to tumour growth and recurrent tumours (Abou-Antoun, Hale, Lathia & Dombrowski, 2017).
Brain tumours in childhood differ from those in adulthood in several ways. In childhood, brain tumours are more a result of genetic and epigenetic factors (ie, how the environment causes genetic changes). In adults, there can be epigenetic factors involved, but brain tumours result more from long-term carcinogen exposure causing genetic damage and mutations leading to cancer (Abou-Antoun, Hale, Lathia & Dombrowski, 2017).
There are more than 40 types of brain tumours, which are grouped into two main types (Cancer Council Australia, 2017):
- Benign - slow growing and unlikely to spread. These include meningiomas, neuromas, pituitary tumours and others.
- Malignant - are able to spread to other parts of the brain or spinal cord. These include astrocytomas, oligodendrogliomas, glioblastomas and mixed gliomas.
Symptoms of brain cancer can vary depending on the location of the tumour, and include the following (Cancer Council Australia, 2017):
- Headaches are often the first symptom. These can be mild, severe, persistent or irregular (but more common or different than usual)
- Difficulty speaking or remembering words, or dementia
- Disturbed vision, hearing, smell or taste
- Seizures or convulsions
- Weakness or paralysis in part of the body
- Loss of balance
- Change in personality
- Nausea and vomiting.
The risk factors of brain cancer include the following (Osiecki, 2012, p334):
- Diet – nutrient deficiencies which affect the central nervous system, immune function or cause chronic inflammation can increase brain cancer risk, such as an imbalance between omega-3 and omega-6 fats in the brain.
- Infections - infectious agents such as viruses have been found in many brain tumours, including cytomegalovirus (CMV) and others (Johnson, Hainfellner, Lau, Scheurer, Woehrer & Wiemels, 2016).
- Environmental chemical exposure – exposure to many environmental chemicals can affect the central nervous system and immune system to increase the risk, including from oil refining, rubber and plastics manufacturing, agricultural chemicals like herbicides and pesticides as adults can result in brain cancers in their children at a young age (Osiecki, 2010, p334).
- Radiation exposure - radiation from medical tests, high voltage power lines, mobile phones and possibly WiFi may increase the risk, but results from studies are conflicting (Johnson, Hainfellner, Lau, Scheurer, Woehrer & Wiemels, 2016). Studies may be conflicting due to the long latency period of brain tumours, and studies being of insufficient follow-up length (of 10+ years) to report a causative link. Some long-term studies have shown a link of extended mobile phone use with the development of gliomas (Yang et al., 2017). The World Health Organisation classifies mobile phone radiation as a possible carcinogen (Johnson, Hainfellner, Lau, Scheurer, Woehrer & Wiemels, 2016).
- Genetics – there are many genetic and epigenetic factors involved in brain cancer, which can cause mutations in cancer promoting genes, cancer suppressor genes and these can affect cancer stem cells (Abou-Antoun, Hale, Lathia & Dombrowski, 2017). Genetic disorders such as Li-Fraumeni syndrome, neurofibromatosis, tuberous sclerosis and Turcot's syndrome are all risk factors for brain tumours (Osiecki, 2012, p334).