What are nervous system tumors?

Nervous system (NS) tumors are classified by the World Health Organization as primary tumors, when they originate from cells within the nervous system itself, and secondary or metastatic tumors, when they originate from cells in other organs and subsequently spread to the nervous system. Primary NS tumors form an extremely heterogeneous group—some exhibit indolent behavior, while others are more aggressive. They most commonly affect the brain and meninges, but can also involve the spinal cord and cranial and spinal nerves.

Secondary (metastatic) tumors are the most frequent in adults and can occur as a progression of virtually any extracranial tumor. The most common sources are lung cancer, breast cancer, and melanoma. Among primary NS tumors, meningiomas and gliomas are the most frequently found in this age group.

Symptoms

The clinical presentation is variable and depends on the tumor’s size, location, and growth rate. Signs of either focal or generalized impairment may be observed. Headache, nausea, vomiting, and seizures are the most frequent symptoms and are usually progressive, meaning they worsen over time. Depending on the tumor’s location, additional signs of functional impairment in the affected region may also appear, such as: motor or sensory changes, vision or hearing disturbances, language difficulties, personality changes, memory deficits, and disorientation.

Diagnosis

The most commonly used methods for evaluating patients with suspected nervous system (NS) tumors are computed tomography (CT) and magnetic resonance imaging (MRI), both performed with contrast. MRI is the preferred method, as it provides a better assessment of the lesion’s extent and involvement of anatomical structures, allowing for more precise surgical planning. Specific MRI sequences, such as spectroscopy, can offer additional information about the lesion’s biochemical and metabolic characteristics. When compared to normal tissue, these findings are useful for both differential diagnosis and patient follow-up. Perfusion MRI also helps detect increased tumor vascularization, which may, in some cases, be associated with greater aggressiveness, such as in gliomas. Other techniques, including functional MRI, tractography, and MR angiography, may also be helpful, particularly in surgical planning.

It is important to note, however, that a definitive diagnosis can only be established through histopathological evaluation of the lesion, performed via biopsy or tumor resection. Primary NS tumors are usually confined to the affected site and do not spread to other organs. Therefore, tests to assess whether other parts of the body are involved (systemic staging) are rarely necessary. However, some tumors may spread within the nervous system itself, and in such cases, a comprehensive evaluation of the entire NS (brain and spinal cord) is performed.

Treatment

The treatment of nervous system (NS) tumors involves two fundamental stages: symptomatic treatment, aimed at improving symptoms and the patient’s quality of life, and specific treatment of the tumor. The main therapeutic approaches typically used are surgery, radiotherapy (RT), and chemotherapy (CT), with the goal of achieving tumor control.

For most patients, treatment begins with neurosurgery, which is essential both for obtaining a histological diagnosis (definitive identification of the tumor type) and for achieving the maximum possible reduction in tumor volume, provided it is technically feasible and carries a low risk of complications.

Radiotherapy, generally used as a complement to surgery, plays a key role in treating many primary NS tumors in adults. It helps control symptoms, reduce the lesion, and increase survival.

Chemotherapy, in turn, contributes to prolonging survival in certain NS tumors. In most cases, it is used during or after radiotherapy, as well as in cases of recurrence.

Advances in medical knowledge have enabled the use of molecular testing to identify genetic alterations that allow for more targeted treatment choices. New therapeutic approaches are also being actively studied in recent years, including novel chemotherapeutic agents, targeted therapy, gene therapy, vaccines, and immunotherapy.

Prevention

Unlike some types of cancer, there is still no known way to prevent primary nervous system (NS) tumors, and early diagnosis through screening tests is not routinely performed.

The risk factors for developing primary NS tumors have not yet been clearly established. So far, exposure to ionizing radiation is the only confirmed risk factor. Some rare hereditary genetic syndromes are also associated with an increased risk of NS tumors, such as Neurofibromatosis type I and II, Tuberous sclerosis, Turcot syndrome, Li-Fraumeni syndrome, Cowden syndrome, Gorlin syndrome and Von Hippel-Lindau disease. Immunodeficiency (congenital or acquired) may also be associated with a higher incidence of a specific type of NS tumor known as primary central nervous system lymphoma. Environmental factors—such as occupational exposure, use of pesticides, contact with nitrous oxide compounds, electromagnetic fields, and traumatic brain injury—have been suggested but not scientifically proven. Regarding cell phone use, there is also no conclusive evidence to date linking it to an increased risk of NS tumors.

According to the World Health Organization (WHO) and the U.S. National Cancer Institute (NCI), the risk should be considered only “possible” until definitively proven.

Therefore, it is recommended, whenever possible, to use headphones or speaker mode and to limit the duration of cell phone use.

Incidence

Secondary or metastatic nervous system (NS) tumors are more common in adults, with an estimated 200,000 new cases diagnosed annually in the United States, according to the American Association of Neurological Surgeons.

The estimated incidence of metastatic NS tumors is not well known in Brazil.

Primary NS tumors, on the other hand, are rarer compared to other visceral tumors and metastatic NS tumors.

In the United States, an estimated 77,670 new cases of primary NS tumors occur each year, according to the most recent report from the U.S. Central Brain Tumor Registry (November 2015). The global estimated incidence in 2012, based on data from GLOBOCAN, was 256,213 new cases that year.

In Brazil, according to the most recent report from the National Cancer Institute (INCA), the estimate for 2016 was approximately 10,270 new cases of primary NS tumors (5,440 in men and 4,830 in women). These numbers represent about 2.5% of all cancer types in men and 2.3% in women, ranking 10th in frequency compared to other visceral tumors.

Primary NS tumors are slightly more common in men, although some specific types, such as meningiomas and pituitary tumors, are more prevalent in women. There is also a higher frequency in adults and the elderly, particularly for certain tumor types such as metastases, meningiomas, and gliomas.

By the Einstein Editorial Board