Each year, more than 100,000 Americans are told they have a brain tumor. It is not clear why many of these tumors occur. Those that originate in the brain, primary brain tumors, may be due to genetic or environmental factors. Others, called secondary brain tumors, are the result of cancer that has spread from other parts of the body.
Brain Tumor Types
There are many different types of brain tumors, which are generally categorized as benign or malignant. Benign brain tumors, while slow growing and non-cancerous, may be inoperable. And unlike benign tumors in other parts of the body, benign brain tumors often recur. Malignant brain tumors grow quickly and are life-threatening. Generally, neither type spreads beyond the brain or spinal cord, meaning that they are unlikely to affect other body organs or systems.
Through the use of neurological exam; sophisticated imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI); and biopsy, doctors are able to provide a specific diagnosis as to the type of brain tumor a person has. Below are descriptions of some brain tumors and their treatment options.
Craniopharyngiomas are tumors near the brain's pituitary gland and most commonly affect infants and children. Because the pituitary gland releases chemicals essential for growth and metabolism, a craniopharyngioma may result in a child's stunted growth. The patient's vision may also be affected. These tumors develop from cells left over from early fetal development.
Treatment: Treatment for these tumors usually includes surgery and fractionated stereotactic radiation therapy. The treatment goal is to gain maximum resection of the tumor while maintaining vision and pituitary function. Dr. Carmel has published the largest series in North America of patients undergoing surgery for craniopharyngioma.
Ependymomas develop from cells that line chambers of the brain or the canal containing the spinal cord. Most of these tumors are benign. Ependymomas often occur in children, where they typically develop at the brain's base.
In addition to headache and vomiting, ependymomas can cause swelling of the optic nerve, involuntary, jerky eye movement known as nystagmus, and neck pain.
Treatment: Surgery followed by radiation therapy is the usual treatment for these tumors. Chemotherapy may be used in the case of recurrent tumors. However, stereotactic radiation therapy may improve tumor control while limiting the side effects of radiation, especially in children.
Gliomas account for about half of all primary brain tumors and nearly one-fifth of all primary spinal cord tumors. They originate from nerve cells called glial cells. Gliomas occur most often in the cerebral hemispheres, but also are found in the optic nerve, the brain stem, and especially among children, the cerebellum.
There are many types of gliomas, including: Astrocytomas
Most gliomas are astrocytomas, which develop from star-shaped glial cells called astrocytes. These tumors can occur in different parts of the brain, and thus, produce varying symptoms. For example, if the astrocytoma is located in the cerebellum (as is commonly the case with children), balance and coordination may be affected. The result of increased intracranial pressure may be headache, vomiting, and visual problems.
Doctors categorize these tumors by grades. Grading occurs after biopsy, when a pathologist examines the brain tissue for breakdown of cell structure. While there are different systems used to assign grades, in general, they are as follows:
Grade I tumors are slow growing; their cells are near-normal in appearance; and are not malignant.
Grade II tumors have cells that are slightly abnormal in appearance and can spread to surrounding tissue.
Grade III tumors grow quickly, contain abnormal cells, and spread to surrounding tissue.
Grade IV tumors contain aggressive, abnormal cells that reproduce quickly. These are the most malignant of brain tumors.
The types of graded astrocytomas include:
These Grade I and II, or low-grade, astrocytomas contain relatively normal cells and are less malignant than the other two grades. While well-differentiated astrocytomas often can be completely removed through surgery, those that are inaccessible to the surgeon may be life-threatening.
These Grade III astrocytomas contain cells with some malignant traits.
Treatment: Surgery followed by radiation, and some chemotherapy, is used to treat anaplastic astrocytomas.
These tumors, sometimes called high-grade or grade IV astrocytomas, grow rapidly, invade nearby tissue, and contain cells that are very malignant. Glioblastoma multiforme is among the most common and devastating primary brain tumors that strike adults. Doctors usually treat glioblastomas with surgery followed by radiation therapy. Chemotherapy may be used before, during or after radiation.
Treatment: For both anaplastic gliomas and glioblastomas , functional image-guided surgery (FIGS) may be helpful in resecting as much tumor as safely possible. Gliadel®, dime-sized chemotherapeutic wafers that are implanted following tumor resection, may be considered for patients with tumors that recur after other treatment.
A rarely occurring and slow-growing form of glioma, gangliogliomas can be found in the brain or spinal cord.
Brain Stem Gliomas
Treatment: These tumors are usually treated with surgery. Functional image-guided surgery may optimize the safety and completeness of surgical resection.
Like their name suggests, brain stem gliomas are located at the base of the brain. They occur more frequently in children than in adults. Brain stem gliomas can range in grade, from slow growing and benign to fast-growing and malignant.
Treatment: Brain stem gliomas occur in a vulnerable location, so surgery is rarely performed to remove them. Radiation therapy can reduce symptoms and improve the patient's chance of survival by slowing tumor growth.
Mixed gliomas contain more than one type of glial cell; one of them usually being astrocytes. For reasons that are not known, mixed gliomas most commonly occur in young men.
Mixed gliomas often produce symptoms common to many brain tumors-headache, vomiting, and visual problems. Depending on the tumor's location, there may be paralysis on one side of the body, memory difficulties, and personality changes.
Optic Nerve Gliomas
Treatment: Treatment focuses on the most malignant cell type found within the tumor and often involves surgical resection. Functional image guided surgery may be used for tumors near the " eloquent" areas of the brain. Radiation therapy is another possibility.
Optic nerve gliomas can interfere with vision, causing "crossed" eyes, or strabismus; bulging eyeballs, or loss of sight. People with neurofibromatosis, a condition where fiber-like growths affect the nerves, may be susceptible to these types of tumors.
Treatment: Treatment may include surgery, radiation or chemotherapy. Stereotactic radiation therapy may control the tumor while avoiding radiation injury to the uninvolved portions of the optic chiasm.
Medulloblastomas, which are malignant, represent more than one-fourth of all childhood brain tumors. They belong to a class of tumors called primitive neuroectodermal tumors, or PNETS, and tend to grow quickly. Medulloblastomas can spread throughout the nervous system and, while not a common occurrence, to other parts of the body.
Some symptoms of medulloblastomas include vomiting, headache, and visual problems. As most of these tumors are located in the cerebellum, muscle coordination-particularly during walking-may be affected. There may also be speech difficulties and weakness in the muscles.
Treatment: Medullobastomas, like other PNETs, are difficult to totally remove through surgery because their cells often spread in a scattered, patchy pattern. Doctors usually remove as much tumor as possible with surgery, then prescribe chemotherapy and/or radiation. Children under age three generally do not receive radiation treatment because of possible long-term side effects. However, stereotactic radiation therapy may be an option, especially for young children without widespread disease; this technique does not produce the same effects as of conventional radiation on the developing brain.
Meninges are thin membranes that cover the brain and the spinal cord. Meningiomas, tumors originating from these membranes, account for about 15 % of all brain tumors and about one-fourth of all spinal cord tumors. These slow-growing tumors rarely become malignant or spread, but about 5 % of the time, malignancy does occur.
Treatment: Surgery is the preferred treatment for accessible meningiomas and is more successful for these lesions than for most tumor types. Recurrent meningiomas may require additional treatment including radiation therapy. In some cases, stereotactic radiosurgery alone may be a good treatment for patients with meningiomas; in others, a strategy of resection plus adjuvant radiosurgery may be ideal. Tumors close to the optic chiasm may be treated with stereotactic radiation therapy, as the high single doses of radiosurgery may injure the chiasm in such cases.
These are malignant tumors that have spread from elsewhere in the body.
These tumors are relatively rare, and when they do occur, are slow growing. Young adults are most commonly affected by oligodendroglimas.
Tumors near the pineal gland, a small structure deep within the brain, can be of about 17 different types. Some are malignant, like the germinoma, and others are not. That is why, when possible, biopsy is used to confirm the tumor type.
Treatment: Benign pineal tumors can often be removed surgically; radiation, chemotherapy, or both, can be the course of treatment for malignant pineal tumors. Patients with the most common types of pineal-region tumors-gliomas, germinomas, and PNET-have been treated successfully with stereotactic radiosurgery. Larger tumors can be treated with stereotactic radiation therapy
The pituitary gland, a small oval-shaped structure located at the base of the brain, releases several chemical messengers known as hormones, which help control the body's other glands and influence the body's growth, metabolism, and maturation. Tumors that affect the pituitary gland account for about 10% of brain tumors. Doctors classify pituitary adenomas into two groups: secreting and non-secreting. Secreting tumors release unusually high levels of pituitary hormones, triggering a constellation of symptoms, which can include impotence, amenorrhea (cessation of the menstrual period), galactorrhea (milk flow unrelated to childbirth or nursing), abnormal body growth, Cushing's syndrome, or hyperthyroidism depending on which hormone is involved. Other tumors that are non-secreting cause symptoms due to their size and so-called "mass effect" on surrounding structures.
Prolactinoma: Currently, patients with prolactin-secreting tumors are often treated with a medication called bromocriptine (brandname: Parlodel) or similar agents such as pergolide or dosinex (a longer-acting preparation), which must be taken lifelong to prevent tumor recurrence. Progressive visual loss, the inability to tolerate the medication, or the chance of a surgical cure may indicate surgical resection. Young women seeking to bear children and to avoid lifelong medication may opt for surgery especially if they have a microprolactinoma (less than 10 mm in height on MRI scan) and a serum prolcatin level less than 300 ng/mL. Such patients may have an excellent chance of cure with surgery. Stereotactic radiosurgery-and in some cases radiation therapy-may play a role in certain patients who have large tumors and cannot tolerate bromocriptine or its related medications.
Acromegaly: This condition is due to oversecretion of growth hormone by a pituitary tumor. If the tumor develops during adolescence the patient may grow to unusual height, a condition known as gigantism. While this may not be inherently a problem, acromegaly, which occurs after growth stops, can be disabling and ultimately lethal. Diabetes, high blood pressure, heart disease, and severe joint abnormalities may ensue. Growth of facial bones may be unsightly. Total resection of a growth-hormone secreting tumor may be curative; other treatments may include stereotactic radiosurgery and/or radiation therapy, which can be highly effective in controlling the disease. Medications such as octreotide or bromocriptine may control the disease to some extent but not nearly as well as in the case of prolactinomas.
Cushing's Disease: Tumors that secrete adrenocorticotrophic hormone (ACTH) stimulate the body's adrenal glands (situated just above the kidneys) to make excessive amounts of cortisol, a steroid that the body normally makes and needs for daily life. However, overproduction of this hormone leads to Cushing's disease, a condition that often is lethal if untreated. Patients develop weight gain due to central obesity, a round-faced appearance, fragile skin, diabetes, and high blood pressure. Surgery is the ideal treatment, especially for those patients with small tumors. Occasionally the entire pituitary gland may need to be removed to achieve a cure, although this should only be done after careful testing confirms that the pituitary is the origin of the problem. Medical therapy with ketoconazole, for instance, may be used as an adjunct. The role of radiation therapy is unclear, although radiosurgery may be useful if surgery is not curative.
Non-secreting tumors: Many patients with pituitary tumors do not suffer from excess hormone production. Rather, their symptoms are due to the "mass effect" of the tumor - i.e., pressure on the optic nerves may cause decreased vision, or the pituitary gland may underproduce normal hormones resulting in problems such as hypothyroidism or decreased sexual drive. If such tumors are found "incidentally", that is, on a scan done for other reasons, treatment may not be needed, especially if the tumor is small. However, if visual loss is present or if MRI demonstrates pressure on the optic nerves, then surgery is often indicated. Radiation therapy or stereotactic radiosurgery can control these tumors but are probably best used as adjuvant treatments after surgery.
Other secreting tumors are much rarer than those listed above, and include:
TSH-producing tumors: Patients with these tumors will have hyperthyroidism because of overproduction of thyroid-stimulating hormone, or TSH (most people with hyperthyroidism have a problem in the thyroid gland itself). The ideal treatment is surgery but radiation therapy or radiosurgery may be needed if TSH levels remain high.
FSH or LH-producing tumors: Follicle stimulating hormone (FSH) or luteinizing hormone (LH) are normally involved in maintenance of sexual function and sexual characteristics in men and women. Their overproduction can alter bodily appearance and interfere with menstrual cycling and pregnancy. The ideal treatment is surgery, but radiation therapy or radiosurgery may be needed if hormonal levels remain high.
Surgery for pituitary tumors: Since pituitary adenomas are underneath the brain, most often they can be surgically approached through the nose and the sphenoid sinus, which lies behind the nose-hence the term "transsphenoidal" surgery. Sometimes an incision under the lip or inside the nose is used to facilitate this surgery, but with the use of modern endoscopic techniques, a nasal incision can be avoided. The tumor itself is removed with the aid of an operating microscope or possibly with the endoscope alone.
The transsphenoidal approach may not be advisable in every case; at times an operation through the head (i.e. "craniotomy") may be preferable if the tumor is unusually large.
Stereotactic radiosurgery for pituitary tumors: Conventional radiation therapy is an effective treatment for many patients with pituitary adenomas. However, large areas of the scalp and brain will also be irradiated. Stereotactic methods make it possible to treat the lesion itself with minimal radiation delivered to surrounding structures. If the tumor is small enough, stereotactic radiosurgery (SRS), may be possible. If the optic nerves or optic chiasm (where the optic nerves meet) are close to the tumor edge, then SRS may not be safe, as the high dose of radiation used would be delivered to these sensitive nerves. If this is the case, then fractionated radiosurgery is advisable.
Stereotactic radiation therapy should be used for the treatment of patients requiring radiation for large pituitary tumors. Radiosurgery may be considered if the lesion is small enough so that injury to the optic chiasm is unlikely to occur from treatment.
Primitive neuroectodermal tumors (PNETs) usually affect children and young adults. Many scientist believe these tumors originate from primitive cells left over from early nervous system development. PNETs are usually very malignant, growing rapidly and spreading easily within the brain and spinal cord. In rare cases, they spread outside the CNS.
These tumors, while usually benign, can affect balance, hearing, and speech. Facial paralysis may occur if the tumor involves the seventh cranial nerve. Also known as vestibular schwannomas or acoustic neuromas, these tumors may grow on one or both sides of the brain.
Symptoms may include tinnuitis-ringing in the ear-; ear pain; and dizziness. Headache and problems with walking can also occur.
Treatment: For most patients, surgical resection by a combined skull base approach is the ideal treatment. Patients who are elderly, medically infirm, or refuse surgery may be treated with stereotactic radiosurgery. Clinical trials show that stereotactic radiation therapy yields excellent tumor control and has a minimal complication rate.
Even after treatment for the tumor, some people may continue to have a hearing loss.
These rare, benign tumors arise from excess growth of blood vessels of the brain. They usually occur in the cerebellum , which is located at the back of the brain. The most common vascular tumor is the hemangioblastoma, which has been associated with von Hippel-Lindau disease, a genetic disorder. Hemangioblastomas do not usually spread.
Because the cerebellum controls balance, people with vascular tumors often walk uncoordinatedly or have difficulty staying steady. Increased pressure within the skull can result in vomiting and headache, as well as visual problems.
Treatment: Surgery is curative. A screening evaluation is recommended to rule out renal cancer, adrenal tumors, and retinal abnormalities. Stereotactic radiosurgery has been shown to control the growth of these tumors.