A malignant brain tumor is the most life-threatening of neoplastic (cancerous) diseases. HOWEVER the most common “brain tumor” is actually a meningioma and is almost always benign. Other brain tumors are somewhere in between. We can determine a great deal based on a tumor’s appearance by MRI (and CT), such as the likely type, location, risk factors and best treatment.
The “real” brain tumors are those that start in the brain, as opposed to the coverings of the brain or from another part of the body. These brain tumors form almost exclusively from supporting brain cells, called glial cells, and not the neurons themselves. The most common tumors, known as astrocytomas, come from a cell called an astrocyte.
The most common astrocytoma is called the glioblastoma multiforme or GBM. The tumors are collectively called gliomas. Gliomas in adults share an important characteristic that is difficult for everyone, doctors included, to understand; they are a diffuse disease. This means that the tumors are not completely concentrated into a ball but send out cells into the entire brain, far away from the main focus of the tumor. This is NOT visible on an MRI scan. Therefore, gliomas in adults can not be cured with surgery; surgery is a focal therapy and the disease is diffuse. A surgical cure for an adult glioma, even in the best cases (small tumor in a silent part of the brain), is rare, if not impossible. Other focal treatments, such as Gamma knife, fail for the same reason. That being said, most brain tumor surgeons have patients who have beat the disease. These patients have needed a combination of technically excellent surgery, radiation and chemotherapy. The technical aspect of the surgery is still crucial, even if a surgical cure is not likely, because you need a surgeon who will remove as much of the tumor as possible without causing new, permanent or disabling deficits.
“Other” brain tumors, such as meningiomas or hemangioblastomas, have a high surgical cure rate. Size and location are the determining factors for surgical curability and risk. For example, a meningioma over the middle of the frontal lobe can almost always be cured, whereas a meningioma at the base of the skull, wrapped around the carotid artery and the nerves to the eyes, cannot be cured. Luckily, meningiomas do not grow steadily and may lay dormant for years. One can live with a relatively benign tumor but it is important not to let them become life-threatening.
Meningiomas can threaten one’s life by causing a seizure at the wrong time (such as while driving) or by compressing the brain (even if the tumor grows slowly, there comes a point at which the brain can no longer tolerate the size of the tumor).
Selecting the right surgeon is crucial to minimize one’s chance of brain damage during a curative operation. Complications from meningioma surgery occur in several related ways: seizures, loss of nerve function or stroke. The tumors push into the brain and may steal arteries and veins from the brain or envelop the nerves coming from the brain to the eyes and face. These risks can be greatly reduced with an experienced surgeon.
Metastatic tumors in the brain are tumors that have spread into the brain from elsewhere, such as from lung cancer. The most important factor in beating such cancer is the type of tumor and the extent of disease spread in the body. There are many times when tumors that have spread to the brain should be removed. The most common criteria are: a small number of tumors in the head (1-3), a location near the surface of the brain and tumors that are not very sensitive to radiation. Even after surgery for metastatic tumors in the brain, patients will need radiation treatment.