By Peter Galvin, MD
Statistics say that 85,000 individuals in the U.S. are diagnosed with a primary brain tumor (originates in the brain, not spread from outside of the brain) each year, of which about 29% are malignant. Tumors are classified as malignant based upon several factors, including microscopic appearance, rate of growth, and ability to spread to distant areas of the body. Although statistically 71% of brain tumors are benign (meningioma being the most common), in reality there is no such thing as a benign brain tumor. This is because the brain is enclosed within a space that is non-expandable (the skull) so that anything that grows within the brain must push healthy brain tissue aside, thereby causing (sometimes irreversible) brain damage. About 80% to 85% of malignant brain tumors are gliomas, of which 49% of those are glioblastomas. Gliomas diffusely infiltrate the brain tissue and usually do not occur as a solid mass, which is why they are usually not amenable to surgical removal. The incidence of glioblastoma increases after age 40 and peaks in adults aged 75 to 84 years. Meningiomas are by far the most common brain tumor, and over 90% are “benign,” yet still cause symptoms because of cranial space issues.
Less than 5% of adults with malignant brain tumor report a family history of brain tumors or have a cancer predisposition syndrome. However, based on genetic research, the contribution of heredity to brain tumor formation is likely higher than 5%. Prior exposure to ionizing radiation to the brain, such as during treatment for another cancer such as childhood leukemia, is a risk factor. It has been established that exposure to low-frequency electromagnetic radiation fields (i.e., cell phone) is not a risk factor. This was proven by the UK Million Women Study which found no difference in relative risk of gliomas, meningiomas, pituitary tumors, or acoustic neuromas based upon cellphone use. As far as brain tumor symptoms go, one would expect to find headache a universal occurrence, but headache is reported in only about 50% of those with newly diagnosed brain tumors. Other symptoms depend on the location and speed of growth of the tumor, for example rapidly growing tumors may raise intracranial pressure causing nausea, vomiting and fatigue, frontal tumors may cause personality changes, and other tumors may cause a myriad of neurological symptoms including seizures (75% of those with gliomas have seizures).
Diagnosing brain tumors usually involves contrast-enhanced MRI scanning. The IV contrast usually enhances the image of the tumor and often shows cerebral edema (swelling) surrounding the tumor. In order to establish the diagnosis, a brain biopsy is commonly required, even if the tumor is deemed to be non-resectable. The biopsy is required to grade the tumor which helps establish the prognosis. Because most brain tumors cause cerebral edema, corticosteroids are usually prescribed; Dexamethasone is preferred due to its long half-life and low incidence of side effects. For non-resectable tumors, whole brain irradiation is given along with chemotherapy. Despite many advances in treatment, five-year survival rate of some brain tumors remains dismal. For example, the five-year survival rate of glioblastoma with treatment is less than 10%. Thankfully, the incident rate of primary malignant brain tumor is low at seven per 100,000 individuals.
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