Glioma

Glioma is a serious type of tumor that develops in the central nervous system. It originates from glial cells, which are responsible for supporting neurons and helping them to maintain their proper functioning. They can affect brain function and can be life-threatening, although their characteristics and approach depend on the type of glioma and its location. They are rare, affecting 6 out of every 100,000 people.

As with most brain tumors, the exact cause of the development of gliomas is unknown, although it is postulated that they are the result of the interaction of genetic and environmental factors. In addition, risk factors have been identified that may contribute to their occurrence:

  • The diagnosis of glioma is more frequent after the age of 45, although it can occur at any age. There are certain types of gliomas, such as ependymomas, which are more common in children and young adults.
  • Exposure to ionizing radiation. This is the most important risk factor in the development of gliomas. People exposed to this type of radiation (X-rays, radiotherapy for cancer, radiation caused by atomic bombs, etc.) have a higher risk of suffering this type of tumor.
  • Syndromes that increase the predisposition to develop tumors such as Lynch syndrome or Li-Fraumeni syndrome.

The exact cause of gliomas is unknown, although some risk factors that may favor their development have been identified. The vast majority of gliomas are of sporadic origin, with no family history, which highlights the low heritability of the pathology. However, it has been established that having a family history of glioma can double the risk of developing it. Association studies carried out in recent years have identified some susceptibility variants. A GWAS-type study carried out on about 12500 patients and more than 30000 controls has identified 9 associated loci. These include genes involved in telomere length maintenance, such as TERT, and cell cycle regulators, such as CDKN2B-AS1, which is also associated with other types of cancer.

Symptoms

The symptoms of glioma vary according to its location and the type of tumor, although the most common are the following:

  • Headache.
  • Nausea or vomiting.
  • Confusion or decreased brain function.
  • Memory loss.
  • Personality changes.
  • balance problems
  • seizures
  • slurred speech
  • vision problems

Symptoms may worsen or change as the tumor grows and compresses different parts of the brain, increasing swelling and pressure in the skull. If the tumor develops in the spinal cord, it can cause pain, weakness and numbness of the extremities.

Prevention

There is no total preventive measure for the development of gliomas, however, in some cases avoiding modifiable risk factors may help to reduce it. At the moment, the only identified risk factor clearly associated with the development of these tumors is exposure to ionizing radiation.

Exposure to this type of radiation can occur by different routes:

  • Internal exposure: occurs when the radionuclide is inhaled, ingested or injected.
  • External exposure: occurs when the radioactive material is present in the environment.

The people most exposed to this type of radiation are astronauts (from cosmic radiation), X-ray medical personnel, researchers and radioactive facility personnel. In addition, additional exposures may be received at each X-ray and nuclear medicine examination.

Number of observed variants

13.5 million variants

Number of risk loci analyzed in the study

9 loci

Bibliography

Melin BS, Barnholtz-Sloan JS, Wrensch MR, et al. Genome-wide association study of glioma subtypes identifies specific differences in genetic susceptibility to glioblastoma and non-glioblastoma tumors. Nature Genetics. 2017 May;49(5):789-794.

Louis DN, Perry A, Wesseling P, et al. The 2021 WHO Classification of Tumors of the Central Nervous System: a summary. Neuro Oncol. 2021 Aug 2;23(8):1231-1251.

American Cancer Society [April 2022]

Mayo Clinic [April 2022]

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