Brain tumors | risk factors and Genetics

Brain cancer ranks as the second most common cancer among children under 14 years old, following leukemia, while it is considered the eighth most common type of cancer among people over 40 years old. Approximately 308.000 people are diagnosed with brain cancer annually worldwide.

There are more than 120 known types of brain cancer according to the latest statistics from the World Health Organization. Most of these types of brain cancer have unknown causes, but some types may result from genetic factors, such as having a relative with brain cancer, which increases an individual's likelihood of developing it.

In this article, we will highlight the causes of brain cancer, its types, and the importance of genetic testing in early diagnosis, prevention, and changing treatment methods.

 

How Does Brain Cancer Develop?

Brain cancer develops from the uncontrollable growth of cancerous cells. It can occur in the brain tissues or in areas nearby, such as the pituitary gland, pineal gland, nerves, and the protective membranes covering the brain's surface.

Tumor cells can grow in the brain, and in this case, they are called primary tumors. These are usually benign, non-cancerous tumors that grow slowly. However, over time, they may develop into malignant, fast-growing cancerous tumors that compress and completely destroy brain tissues. Tumors can also spread from other parts of the body to the brain, known as metastatic or secondary tumors.

 

Types of Brain Cancer

There are more than 120 types of brain cancer, which vary based on the type of tumor cells and their growth location. The most notable types of brain cancer include:

Gliomas

This type of brain tumor originates in the glial cells, which are the supportive and protective cells for the brain tissues. Gliomas are the most common type of malignant brain tumors. Several subtypes of gliomas include:

• Astrocytomas: These tumors arise from the growth of cancerous cells in astrocytes, which are responsible for repairing and nourishing brain cells. They account for nearly half of primary brain tumor cases.
  
  
• Glioblastomas: These are the most dangerous type of astrocytomas. They originate in the spinal cord or brain and share symptoms with other gliomas, such as persistent headaches, seizures, nausea, and blurred vision.
  
  
• Ependymomas: These tumors are most common among children and affect the ependymal cells lining the ventricles that carry cerebrospinal fluid, which protects the brain and spinal cord from damage.
  
  
• Oligodendrogliomas: This type of brain tumor develops in oligodendrocytes, which are responsible for producing a protective substance for the nerve cells in the brain and for transmitting electrical signals in the brain and spinal cord.

Meningiomas

Meningiomas are a type of brain tumor that affects the meninges, the protective membranes surrounding the brain, located just beneath the skull. Meningiomas are the most common type of benign brain tumors and typically grow slowly, though they can occasionally develop into malignant tumors.

Medulloblastomas

Medulloblastomas are a type of brain tumor that affects the cerebellum, located at the base of the skull. These tumors can spread to the central nervous system, which includes the brain and spinal cord. Medulloblastomas account for about 20% of brain tumors in children.

Neuroblastomas

Neuroblastomas usually arise due to the incomplete development of certain nerve cells in various parts of the body. They most often affect the adrenal glands, abdomen, chest, neck, or areas near the spine.

Pituitary Tumors

Pituitary tumors are typically benign and occur in the pituitary gland and its surrounding area. The pituitary gland is responsible for secreting hormones necessary for vital body functions, such as growth and blood pressure regulation, and these tumors can impact its ability to produce these hormones efficiently.

Other Rare Brain Tumors

There are other rare types of brain tumors that can affect muscles, blood vessels, skull bones, and other structures within the brain.

 

Causes of Brain Cancer

There are various causes of brain cancer, with some of the most prominent being:

Aging

Brain cancer can occur at any age, but the likelihood of developing it increases with age.

Obesity

Obesity can increase the risk of certain types of brain cancer, such as meningiomas.

Radiation Therapy

Exposure of the brain to radiation therapy can increase the probability of developing brain cancer.

Genetic Factors

Genetic factors contribute to 5% of brain cancer cases. The risk of developing brain cancer is higher if there are first-degree relatives (such as parents or siblings) who have brain cancer or genetic conditions that increase the risk of brain cancer. These conditions include neurofibromatosis types 1 and 2, tuberous sclerosis, Li-Fraumeni syndrome, Turner syndrome, von Hippel-Lindau syndrome, Turcot syndrome, and Gorlin syndrome.

Some of the key genes responsible for an increased risk of brain cancer when mutated include: MSH6, MSH2, C2orf80, LRIG1, TERC, VHL, TP53, APC, MLH1, PMS2, TSC1, and TSC2.

 

Importance of Genetic Testing in Early Diagnosis and Treatment of Brain Cancer

Genetic testing can significantly alter the ways in which brain cancer and other types of cancer are diagnosed, treated, and prevented. Here are the key benefits:

Prevention and Early Diagnosis

Genetic testing can identify genetic changes that cause brain cancer or increase the risk of developing it, allowing for tailored recommendations to individuals and families. It can also determine the likelihood of a brain cancer survivor experiencing a recurrence by detecting any other genetic changes that may lead to brain cancer or other types of cancer.

Personalized Cancer Treatment

By uncovering the patient's genetic makeup and the changes within it that cause cancer, genetic testing can influence how the patient responds to treatment. This assists doctors in selecting the most appropriate treatment options for the patient, minimizing unwanted side effects from other treatments, and increasing the chances of recovery. For example, initial diagnosis may suggest surgery for a brain cancer patient, but genetic testing might lead the doctor to choose targeted therapy, chemotherapy, or other suitable treatment options.

Assessing Family Risk of Cancer Recurrence

Genetic testing can determine the likelihood of other family members (especially first-degree relatives) developing the same brain cancer or other cancers based on the identified genetic changes causing the cancer. This allows for necessary recommendations for family members, which may include genetic testing or developing a comprehensive cancer prevention plan.

Advancing Cancer Research

Genetic testing contributes to cancer research by identifying new genes that cause brain cancer, leading to the development of more effective treatments, such as gene therapy. Researchers are currently testing the effectiveness of a gene therapy treatment for astrocytomas after its success in treating leukemia.

The American Cancer Society recommends genetic testing in the following cases:

1. For Cancer Patients:

• If you are diagnosed with cancer before the age of 50.
• If you have one or more first-degree relatives (parents or siblings) with cancer.
• If you are diagnosed with rare cancers, such as prostate cancer, breast cancer in men, or rare types of pancreatic cancer.
• If you are planning to undergo surgery to reduce cancer spread (such as colon or breast removal), to determine the appropriate treatment and procedure based on your genetic changes.

2. For Healthy Individuals:

• If you have relatives with brain cancer, pancreatic cancer, prostate cancer, or other cancers.
• If you have more than one first-degree relative (parents or siblings) with cancer.
• If you have a relative diagnosed with more than one type of cancer.
• If you have a relative diagnosed with cancer before the age of 50.

The appropriate type of genetic test depends on the individual's health status and family history of brain cancer or any other genetic syndromes and diseases that increase the risk of brain cancer and other cancers. Therefore, genetic counseling is recommended to guide the individual to the appropriate procedure.

Cancer and Genetic Counseling

Genetic counseling plays a crucial role in guiding you to the appropriate procedure and recommending the most comprehensive genetic test based on the health information provided about you and your family. It also helps in determining the recurrence risk of cancer within the family. The role of a genetic counselor is not limited to the pre-testing phase; they also assist you in understanding the test results, provide necessary recommendations and guidance, and offer psychological support.

To help you preserve your health and the health of your family, Enigma Genomics provides Comprehensive Cancer Panel, covering 109 genes linked to the various cancer types identified to date, along with a virtual genetic counseling service before and after screening. Additionally, Enigma Genomics offers extensive genetic screening services for hereditary diseases, such as: Whole Genome Sequencing, which covers more than 7,500, and Whole Exome Sequencing, which covers 7,000 genetic diseases and others to help you in the journey of maintaining your health and the health of your family.