DR. MOHAMMED RAEES TONSE
Brain tumours are quite diverse affecting all age groups. These tumours pose several challenges from a treatment perspective including rehabilitation and support services of not only the affected person but also the caregiver. However, due to the improvement in neurosurgical, radiotherapy techniques and development of newer chemotherapeutic and biological agents, the outlook of these tumours have improved over the last decade period of time. Moreover, while long term survivors of brain tumours still have considerable issues in several aspects of their activities of daily living and quality of life, there are many of them, who are not only enjoying an excellent quality of life but are also integrating into the mainstream and leading a good social life.
Worldwide Incidence of brain tumours
Brain tumours, though uncommon are not a rare entity. Globally brain tumours account for less than 2% of all cancers (approximately 175000 cases per year worldwide). Its annual incidence is 3.7 per 100,000 for men and 2.6 per 100,000 for women.
How common is Brain Tumour in India?
The incidence of a primary brain tumour in India ranges from 2.5 to 4.1 per 100,000 population for males and 1.4 to 2.6 per 100,000 population for females based on the Indian Council of Medical Research (ICMR) database. It represents < 1% of new cancer cases detected every year in the country. However, there has been a steady increase in the incidence of primary brain tumours over the last decade or so primarily due to higher detection rates, better awareness among individuals and from the widespread availability of excellent diagnostic imaging in India.
In children, brain tumours account for approximately 35% of all types of tumours and are the second most common cancers second only to leukaemias. Data compiled from multiple institutes of India has shown that most common brain tumour in children are astrocytomas (34.7%), followed by medulloblastoma and supratentorial primitive neuro-ectodermal tumours (22.4%), craniopharyngiomas (10.2%) and ependymal tumours (9.8%). The most common astrocytic tumour was pilocytic astrocytoma.
These tumours are quite diverse in nature ranging from benign to malignant tumours.
Benign (Non-cancerous) brain tumours do not contain cancer cells: Majority of the benign tumours can be removed, and they seldom grow back. Cells from benign tumours do not invade tissues around them or spread to other parts of the body. However, benign tumours can press on critical areas of the brain and cause serious and life-threatening neurological problems.
Malignant (cancerous) brain tumours contain cancer cells: They are likely to grow rapidly and crowd or invade the surrounding healthy brain tissue. Very rarely, cancer cells may break away from a primary brain tumour and spread to other parts of the brain, to the spinal cord, or very occasionally even to other parts of the body. A malignant brain tumour is generally more serious and often is life-threatening.
These tumours affect all age groups right from the very young to the very old. Management of these tumours poses several challenges right from treatment to ancillary care including rehabilitation and support services.
In some patients, a low-grade tumour will develop into a high-grade malignant tumour. It is called malignant transformation or progression to malignancy.
Primary and Secondary Brain Tumours
A primary brain tumour is a solid tumour, defined as an abnormal growth of cells within the brain or the central spinal canal. This abnormal and uncontrolled cell division usually occurs in the brain, in blood vessels, in the cranial nerves, in the brain envelopes (meninges), skull bone, pituitary gland, or pineal gland.
When cancer spreads from its original place to another part of the body, the new tumour has the same kind of abnormal cells as the primary tumour. Cancer that spreads to the brain from another part of the body is different from a primary brain tumour. When cancer cells spread to the brain from another organ (such as the lung or breast) doctors may call the tumour in the brain a secondary tumour or brain metastasis.
In India, primary brain tumours are far more common than brain metastasis which is in contrast to the western countries where metastatic brain tumours are more common.
Risk Factors & Possible Causes of Brain Tumours
There are no known causes of brain tumours. Unlike some of the tumours in the body, it is not caused by an infection or infectious agent. Brain tumours are not contagious and cannot be transmitted from one person to another. Brain tumours can occur at any age. Certain brain tumours like gliomas usually occur in middle age and elderly individuals while certain tumours occur during childhood and adolescence.
1. Exposure to Medical Radiation
Exposure to radiation is the only definite risk factor for the development of second cancers especially brain tumours. People who are exposed to radiotherapy, frequent CT scans or X-rays of the head are at higher risk of developing brain tumours like meningiomas and to a lesser extent, malignant gliomas Although medical exposure to radiation is kept as low as possible, X-rays and CT scans are important modalities in diagnosing diseases so that you have the right treatment.
2. Previous cancers
Children who have had cancer have a higher risk of developing a brain tumour later in life. For e.g. children who have had leukaemia (a type of blood cancer) or Hodgkin or Non-Hodgkin lymphoma (a type of cancer of the lymph nodes) as an adult also have an increased risk of brain tumour. There is some evidence that there is an increased risk of brain tumours in adults who have had other types of cancer for e.g. breast cancer survivors who have been treated with chemotherapy
may have an increased risk of pituitary adenomas. This increased risk has been postulated due to the treatment for previous cancer, such as radiotherapy to the head. However, it should be kept in mind that the benefit of treatment for original cancer far outweighs the risk of brain tumour.
3. Genetic conditions and family history
Less than 1% of brain tumours is associated with genetic conditions and occurs in members of a family. Patients with a family history of any of brain tumours need to get themselves properly investigated with relevant investigations.
4. Other Medical Conditions and Medicines
People with HIV or AIDS have double the risk of being diagnosed with a particular type of brain tumour called lymphoma of the brain which is also called as Primary CNS lymphoma. HIV patients tend to have this form of a brain tumour at a younger age.
There is a small risk of women developing brain tumours especially meningiomas. Post menopausal women who are taking hormone replacement therapy (HRT) or a younger woman who are taking oral contraceptive pills (OCP) may have a slightly increased risk. However, this link needs to be proved by further research studies.
5. Mobile Phones
Cell phones emit radiofrequency electromagnetic radiation. The amount of radiofrequency electromagnetic radiation a cell phone user is exposed to depend on the technology of the phone, the distance between the phone’s antenna and the user, and the user’s distance from cell phone towers. International Agency for Research on Cancer (IARC) has categorized the radiation emitted from cell phones as a category 2B carcinogen, which means that there is inadequate evidence of carcinogenicity in humans but sufficient evidence in experimental animals. From the evidence so far, we still can’t say that mobile phones pose a problem to health. There has been a concern about them causing brain tumours in particular. But there is no strong evidence that there is any link. More research is needed because cell phone technology and the way people are using cell phones have been changing rapidly. Even though there is no strong evidence suggesting that radiations emitted from cell phones increase the risk of brain cancer, individuals need to be cautious while using cell phones.