Most brain tumors are not linked with any known risk factors and have no obvious cause. But, there are a few factors that can raise the risk of brain tumors.
Even if a person has a risk factor, it is often very hard to know how much it contributed to the tumor.
Radiation Exposure
The best known environmental risk factor for brain tumors is radiation exposure most often from radiation therapy to treat some other condition. Before the risks of radiation were known, children with ringworm of the scalp (a fungal infection) were sometimes treated with low-dose radiation therapy, which increased their risk of brain tumors as they got older.
Now a days, most radiation-induced brain tumors are caused by radiation to the head given to treat other cancers esp treatment for leukemia. These brain tumors usually develop around 10 to 15 years after the radiation. Radiation-induced tumors are still fairly rare, but because of the increased risk (as well as the other side effects), radiation therapy to the head is only given after carefully weighing the possible benefits and risks.
The possible risk from exposure to imaging tests, such as x-rays or CT scans, is not known for sure. Some studies claim that it increases risk for tumours like meningiomas and gliomas. These tests use much lower levels of radiation than those used in radiation treatments, so if there is any increase in risk, it is likely to be very small.
Immune System Disorders and Drug Induced
People with impaired immune systems have an increased risk of developing lymphomas (cancers of lymphocytes) of the brain or spinal cord. A weakened immune system can be congenital (present at birth), or it can be caused by treatments for other cancers, treatment to prevent rejection of transplanted organs, or diseases such as AIDS.
Giving the cancer drug methotrexate into the fluid around the spinal cord (intrathecal methotrexate) for the treatment of leukaemia has been shown to increase the risk of brain tumours. But any increase in brain tumour risk from cancer treatment is small compared to the risk of not having the treatment for the original cancer.
Post menopausal women who are taking hormone replacement therapy (HRT) or oral contraceptives may have a slightly increased risk of developing meningioma but more research is needed to confirm
Family History
Most people with brain tumors do not have a family history, but in rare cases (5 per cent) brain cancers run in families. In general, patients with familial cancer syndromes tend to have many tumors that first occur when they are young.
Other factors
Environmental factors such as exposure to solvents, pesticides, oil products, rubber, or vinyl chloride, petroleum products, and certain other chemicals have been linked with an increased risk of brain tumors.
‘Unproven’ Factors
Cell phone use: This has been the subject of a great deal of debate in recent years. Cell phones give off radiofrequency (RF) rays, a form of energy on the electromagnetic spectrum between FM radio waves and those used in microwave ovens, radar, and satellite stations. Cell phones do not give off ionizing radiation, the type that can cause cancer by damaging the DNA inside cells. The phones, whose antennae are built-in and therefore are placed close to the head when being used, might somehow raise the risk of brain tumors.
In 2011, International Agency for Research on Cancer (IARC) classified mobile phone radiation as Group 2B - possibly carcinogenic. That means that there “could be some risk”, so additional research into the long-term, heavy use of mobile phones needs to be conducted.
Studies to date provide no indication that environmental exposure to RF fields, such as from base stations, increases the risk of cancer or any other disease.
There are some inconclusive studies that Cell phone users had a mild increased risk of malignant gliomas. ,and acoustic neuromas.
Tumors are more likely to occur on the side of the head that the cell handset is used.
One hour of cell phone use per day may increases tumor risk after ten years or more. The same is true of any possible higher risks in children, who are increasingly using cell phones.
Body Size: Overweight gives a slightly higher risk of meningioma than in smaller people. But being overweight doesn’t seem to affect glioma risk. Children weighing 4kg or more at birth have a small increased risk of some brain tumour types compared with lighter babies. Taller people might have an increased risk but the evidence on this is still mixed. Studies that look at food and drink in relation to brain tumour risk are not felt to be reliable. This is because brain tumours are relatively rare and measuring diet accurately is very difficult.
Diet,Smoking and Alcohol: Some studies of diet and vitamin supplementation seem to indicate that dietary N-nitroso compounds may raise the risk of both childhood and adult brain tumors.
Dietary N-nitroso compounds are formed in the body from nitrites or nitrates found in some cured meats, cigarette smoke, and cosmetics.
It’s not yet clear whether smoking affects brain tumour risk. But some studies have shown increased risks for some types of brain tumour. Drinking alcohol doesn’t seem to affect risk.
– Dr Arun Oommen, Consultant Neurosurgeon Lakeshore Hospital and Research Centre, Kochi