Brain tumours are clusters of cells in the brain or its covering , whose growth is uncontrolled, causing harm by destroying normal brain tissue, infiltrating between neural tissues, or exerting pressure locally or globally. It is crucial to differentiate between benign and malignant tumours, as not all brain tumours are cancers. Benign tumours grow slowly, do not damage normal tissues, and usually do not require adjuvant radiotherapy or chemotherapy if completely removed. On the other hand, malignant tumours always necessitate adjuvant therapy to delay or prevent recurrence, even after complete resection. It should be noted that certain low-grade tumours have the potential to become malignant over time.

There are over 100 different types of brain tumours, each with further subclassifications. The associated risk factors vary accordingly, but detailed studies have only been conducted on the more common tumours, and only a few risk factors have been identified.

There are more than 100 varieties of brain tumours, with deeper subclassifications. The risk factors vary accordingly; but only the more common tumours have studied in detail, and only some risk factors have been identified.

Age

Brain tumours can occur at any age, but they have a bimodal peak in age-wise incidence; i.e, they are common in children( <15yrs) and elderly( >60yrs), with reduced incidence in between. However, age itself is not a direct cause of brain tumours, just a notable association.

Gender

Malignant brain tumours are slightly more prevalent in males, including those that spread to the brain from other primary cancers. However, certain tumours such as meningiomas, which rely on estrogen receptors for growth, are expectedly more common in females. Prolonged exposure to female hormones like estrogen and progesterone, as seen in cases of early onset of menstruation, late menopause, or use of oral contraceptive pills, is associated with a slightly increased risk of meningiomas. Similar associations have been observed with obesity. Gliomas, on the other hand, do not exhibit a gender difference. In pediatric cases, medulloblastomas are more commonly found in male children, although the exact reason for this remains unclear.

Genetic factors

As such, all tumours have a genetic basis for their dysregulated growth, and most are not genetically transmissible. But, when we talk of genetic risk factors, we only talk about the hereditarily transmissible abnormalities, that makes one prone to develop brain tumours. Most such tumours with a hereditary background, are benign or low grade.Some of the common genetic syndromes associated with brain tumours are:

• • Neurofibromatosis
• • Li-Fraumeni syndrome
• • Turcot syndrome
• • Tuberous sclerosis
• • Von Hippel-Lindau syndrome
• • Gorlin syndrome
• • Turner syndrome

It is worth noting that these syndromes are still rare, and less than 5% of tumours are associated with genetic hereditary conditions. A key characteristic of tumours associated with these conditions is their tendency to be multiple, and new lesions may form over time.

Health conditions

Certain health conditions can either increase or decrease the risk of developing brain tumours. Here are some examples:

• •Obesity is associated with a slightly higher risk of meningiomas.
• •Autoimmune conditions, particularly atopic dermatitis, are linked to a slightly lower risk of gliomas.
• •Low CD4+ counts, which exist before any therapy, are associated with a higher incidence of glioblastomas.
• •Immunocompromised individuals, whether due to biological factors like HIV or chemical factors like chemotherapy, are more susceptible to lymphomas.
• •Having a history of Varicella zoster infection (Chickenpox) is associated with a notable reduction in the risk of gliomas.

Diet & lifestyle

In general, diet is not considered a direct risk factor for brain tumours. However, there is a known neuro-carcinogen called N-nitroso compounds that forms in processed meat due to its "heme" content. On the other hand, the antioxidants found in vegetables and fruits may help mitigate the potential effects to some extent. Interestingly, a higher socioeconomic status has been associated with a higher incidence of brain tumours, although the underlying reasons for this correlation remain unidentified.

Alcohol consumption is not directly implicated as a risk factor for brain tumours. Regarding cigarette smoking, its impact on meningiomas is inconsistent. It slightly protects females against meningiomas, while marginally increasing the risk for men.

Ionising radiation

Ionizing radiation includes X-rays and gamma rays. Gamma rays can originate from various sources such as environmental factors like nuclear waste or nuclear explosions, exposure to radioactive substances used in medical treatments or diagnostics, and experimental laboratory settings. X-rays are commonly used in diagnostic procedures like CT scans or X-rays.

Gamma rays are linked to a higher risk of developing gliomas, meningiomas, and schwannomas. Additionally, prior exposure to gamma rays as an adjuvant therapy can potentially lead to the development of new primary brain tumours. This underscores the importance of radiation dosimetry and advanced treatment methods like Proton beam therapy or radiosurgery using conformal radiation techniques.

It is worth noting that even CT scans, particularly in children under 5 years of age or with multiple scans, have been associated with an increased incidence of brain tumours. Occupational exposure to repetitive X-rays has also been linked to an elevated risk of brain tumours.

Non-ionizing radiation

The rise in cell phone usage has raised concerns about its potential impact on brain tumours. Numerous studies have been conducted, but overall, there is insufficient evidence to establish a clear association between cell phone usage and brain tumours. Similar studies examining the effects of cell phone towers, microwaves, radars, and other related technologies have also yielded inconsistent results. Furthermore, despite the widespread use of cell phones, there has not been a proportional increase in the occurrence of brain tumours over the years. Currently, it is reasonable to consider cell phones as safe in relation to the risk of developing brain tumours.

Conclusion

At present, the only modifiable risk factors for a brain tumour, are exposure to ionising radiation, and possibly obesity. So, it goes without saying that a healthy life style, with plenty of fruits and vegetables, would serve to reduce the risk for brain tumours. Most of the non-modifiable risk factors are typically used for prognostic purposes rather than prevention.