Brain tumor overview
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Brain tumor Microchapters |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
A brain tumor is any intracranial tumor created by abnormal and uncontrolled cell division, normally either in the brain itself (neurons, glial cells (astrocytes, oligodendrocytes, ependymal cells), lymphatic tissue, blood vessels), in the cranial nerves (myelin-producing Schwann cells), in the brain envelopes (meninges), skull, pituitary and pineal gland, or spread from cancers primarily located in other organs (metastatic tumors). Primary (true) brain tumors are commonly located in the posterior cranial fossa in children and in the anterior two-thirds of the cerebral hemispheres in adults, although they can affect any part of the brain. In the United States in the year 2005, it was estimated that there were 43,800 new cases of brain tumors (Central Brain Tumor Registry of the United States, Primary Brain Tumors in the United States, Statistical Report, 2005 - 2006) [1], which accounted for 1.4 percent of all cancers, 2.4 percent of all cancer deaths[2], and 20–25 percent of pediatric cancers[2][3]. Ultimately, it is estimated that there are 13,000 deaths/year as a result of brain tumors[1].
Historical Perspective
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Classification
Brain tumors can be classified into two main categories: primary and secondary tumors. Primary tumors originate in astrocytes, oligodendrocytes and ependymal cells. Secondary tumors originate in malignant cancers located primarily in other organs.
Epidemiology and Demographics
Epidemiological record suggests a growing share each year of infants and children in the United States affected by brain tumors.
Natural History, Complications and Prognosis
Survival rates in primary brain tumors depend on the type of tumor, age, functional status of the patient, the extent of surgical tumor removal, to mention just a few factors[4]. Patients with benign gliomas may survive for many years[5][6] while survival in most cases of glioblastoma multiforme is limited to a few months after diagnosis.
Diagnosis
Staging and Grading
Staging is a way of describing a tumor, such as where it is located, if or where it has spread, and whether it is affecting the functions of other organs in the body. A staging system is used for most other types of cancer. There is a formal staging system for adult brain tumors; however, the grading system is always used instead.
After a brain tumor has been diagnosed, additional tests will be done to learn more about the tumor. If the tumor is a glial brain tumor, the pathologist will assign a “grade” using a number from I to IV (one to four). The grade indicates how different the tumor cells are from healthy cells, with a higher grade tumor having cells that are the least like healthy cells. The characteristics of the tumor, as seen under the microscope, help determine how cancerous a tumor is. Generally, the lower the grade, the better the prognosis (chance of recovery or long-term control of the tumor).
History and Symptoms
Although there is no specific clinical symptom or sign for brain tumors, slowly progressive focal neurologic signs and signs of elevated intracranial pressure, as well as epilepsy in a patient with a negative history for epilepsy should raise red flags. However, a sudden onset of symptoms, such as an epileptic seizure in a patient with no prior history of epilepsy, sudden intracranial hypertension (this may be due to bleeding within the tumor, brain swelling or obstruction of cerebrospinal fluid's passage) is also possible.
CT and MRI
Imaging plays a central role in the diagnosis of brain tumors. Early imaging methods—invasive and sometimes dangerous—such as pneumoencephalography and cerebral angiography, have been abandoned in recent times in favor of non-invasive, high-resolution modalities, such as computed tomography (CT) and especially magnetic resonance imaging (MRI).
Other Diagnostic Studies
Electrophysiological exams, such as electroencephalography (EEG) play a marginal role in the diagnosis of brain tumors. The definitive diagnosis of brain tumor can only be confirmed by histological examination of tumor tissue samples obtained either by means of brain biopsy or open surgery. The histologic examination is essential for determining the appropriate treatment and the correct prognosis.
Treatment
Medical Therapy
Although there is no generally accepted therapeutic management for primary brain tumors, a surgical attempt at tumor removal or at least cytoreduction (that is, removal of as much tumor as possible, in order to reduce the number of tumor cells available for proliferation) is considered in most cases[7]. However, due to the infiltrative nature of these lesions, tumor recurrence, even following an apparently complete surgical removal, is not uncommon. Postoperative radiotherapy and chemotherapy are integral parts of the therapeutic standard for malignant tumors. Radiotherapy may also be administered in cases of "low-grade" gliomas, when a significant tumor burden reduction could not be achieved surgically.
Surgery
Meningiomas, with the exception of some tumors located at the skull base, can be successfully removed surgically, but the chances are less than 50%. In more difficult cases, stereotactic radiosurgery, such as Gamma Knife radiosurgery, remains a viable option. Most pituitary adenomas can be removed surgically, often using a minimally invasive approach through the nasal cavity and skull base (trans-nasal, trans-sphenoidal approach). Large pituitary adenomas require a craniotomy (opening of the skull) for their removal. Radiotherapy, including stereotactic approaches, is reserved for the inoperable cases.
References
- ↑ 1.0 1.1 Greenlee RT, Murray T, Bolden S, Wingo PA. Cancer statistics, 2000. CA Cancer J Clin 2000;50:7-33. PDF. PMID 10735013.
- ↑ 2.0 2.1 American Cancer Society. Accessed June 2000.
- ↑ Chamberlain MC, Kormanik PA. Practical guidelines for the treatment of malignant gliomas. West J Med 1998;168:114-120. PMID 9499745.
- ↑ Nicolato A, Gerosa MA, Fina P, Iuzzolino P, Giorgiutti F, Bricolo A. Prognostic factors in low-grade supratentorial astrocytomas: a uni-multivariate statistical analysis in 76 surgically treated adult patients. Surg Neurol 1995;44:208-21; discussion 221-3. PMID 8545771.
- ↑ Janny P, Cure H, Mohr M, Heldt N, Kwiatkowski F, Lemaire JJ, Plagne R, Rozan R. Low grade supratentorial astrocytomas. Management and prognostic factors. Cancer 1994;73:1937-45. PMID 8137221.
- ↑ Piepmeier J, Christopher S, Spencer D, Byrne T, Kim J, Knisel JP, Lacy J, Tsukerman L, Makuch R. Variations in the natural history and survival of patients with supratentorial low-grade astrocytomas. Neurosurgery 1996;38:872-8; discussion 878-9. PMID 8727811.
- ↑ Nakamura M, Konishi N, Tsunoda S, Nakase H, Tsuzuki T, Aoki H, Sakitani H, Inui T, Sakaki T. Analysis of prognostic and survival factors related to treatment of low-grade astrocytomas in adults. Oncology 2000;58:108-16. PMID 10705237.