Brain Tumor Chemotherapy, Early Diagnosis, Symptoms

by Food and Drug Administration (FDA)

(Page 3 of 3)

Radiation destroys cancer cells, but it can also damage adjacent healthy cells. To minimize this damage, doctors may use a special type of radiation treatment called stereotactic radiosurgery or radiotherapy to destroy tumors. One technique combines computer-based treatment planning and a therapy device called the Gamma Knife. Despite its name, this device is not a knife.

The patient is placed on a couch and is fitted with a curved steel helmet, much like a hair dryer, but with 201 small holes. The couch slides into a globe that beams 201 precisely focused gamma rays from radioactive cobalt through the holes to the targeted tumor. One session usually lasts from 15 to 45 minutes and can be repeated, if necessary.

The Gamma Knife is especially effective in shrinking or destroying small, well-circumscribed tumors (less than one and one-quarter inches in diameter) and tumors deep in the brainstem or in other inoperable sites. Radiosurgery can also be used after conventional radiation therapy to boost its effects. More than 41,000 people worldwide were treated with the gamma knife between 1968 and 1995.

Two other machines used in stereotactic radiosurgery — the cyclotron, used to accelerate particles, and a modified linear accelerator — also operate on the same principle as the gamma knife: the delivery of concentrated doses of radiation while sparing normal tissue.

Chemotherapy

Chemotherapy uses drugs to kill tumor cells. Drugs can be given by mouth, injected into a blood vessel or muscle, injected directly into the cerebrospinal fluid, or infused through a catheter to arteries supplying the brain with blood.

One stumbling block to the effectiveness of chemotherapy is the blood-brain barrier, an elaborate network of fine blood vessels and cells that keeps damaging substances in the blood from reaching the brain, but can keep out beneficial drugs as well.

"An important development in the treatment of malignant brain tumors has been the advent of intra-operative interstitial chemotherapy, which circumvents that old bugbear, the blood-brain barrier," says Brem. "This represents a new technology that I and many others in 45 major centers participated in. The study, completed in 1994, was a prospective, randomized, double-blind study [no one knew who received the placebo, or who received the drug] in which biodegradable slow-release polymers [Gliadel wafers] were implanted into the tumor bed after surgery. The surgeon can remove all the gross disease, but 90 percent [of tumors] recur within 2 centimeters. These slow-release wafers, which are impregnated with chemotherapy — BCNU [carmustine] — have been shown to prolong survival." Gliadel wafers are now approved for use in patients who undergo surgery for recurrence of glioblastoma multiforme.

Doctors can treat patients who have certain types of malignant primary brain tumors (and some benign tumors that progress despite surgery and radiation) with chemotherapy before, during or after surgery or radiation. Chemotherapy has been successful in young children and is preferred in many cases to radiation, which can injure developing brains.

The doctor must maintain a delicate balance between giving enough chemotherapy to kill cancer cells, but not so much as to destroy healthy cells. Drugs can be used alone, but are also used in combinations, which are often more effective against the tumor. Other medications that do not affect the tumor but relieve symptoms are corticosteroids to reduce brain swelling and anticonvulsants to prevent seizures.

Cancerous tumor cells, which divide rapidly, can be killed by chemotherapy, but some normal rapidly dividing cells, such as blood, hair follicles, skin, and the cells lining the digestive tract, can also be affected. That's why chemotherapy sometimes causes hair loss and other side effects, such as nausea and vomiting, loss of appetite, diarrhea, anemia, mouth sores, and lowered resistance to infection.

Early Diagnosis Makes a Difference

About half of all primary brain tumors are relatively benign tumors that can be successfully treated, according to the American Brain Tumor Association. Many malignant tumors, including malignant primary brain tumors, such as medulloblastoma in children, are curable by surgery, radiation therapy, and chemotherapy. The most important predictors of a successful outcome are early diagnosis — based on the physician's awareness of common symptoms, as in Sylvia Zeidner's case — and proper management of the disease by a multidisciplinary team of doctors skilled in all phases of diagnosis and treatment.

Zeidner has been having mild headaches since her surgery a year ago, but a recent MRI did not show any recurrence of her meningioma. The neurosurgeon explained that the tumor's removal had left a large cavity in her brain, which has been filling with more fluid than the brain could absorb, thus causing the headaches.

If the headaches get worse, the excess fluid could be drained by a shunt, a tube that is inserted into the head and then threaded under the skin to another body cavity, most commonly the abdomen, where the fluid drains and is absorbed.

Though implanting a shunt is a relatively minor procedure, Zeidner feels she is not that much bothered by her headaches and has opted to treat them with over-the-counter painkillers, which are effective, rather than undergo another round of surgery.

Distinguishing Symptoms

Brain tumor symptoms may resemble symptoms of so many other disorders, including stroke and less life-threatening diseases, that it may be difficult for the doctor to make a diagnosis. For example, headaches — the most common symptom — may be caused by sinus infections or migraine, nausea may be due to gallbladder disease, and dizziness may be a symptom of Meniére's disease.

A CAT scan or MRI can help establish the presence of a brain tumor that may be responsible for any of these symptoms:

• Headaches. Meriting a visit to the doctor include headaches that are: worse in the morning and then improve during the day; persistent and accompanied by nausea and vomiting, especially sudden vomiting; and accompanied by double vision, weakness or numbness.
• seizures (convulsions), especially in an adult
• gradual loss of movement or feeling in an arm or leg
• stumbling, unsteadiness or imbalance
• vision or hearing loss
• speech difficulty
• personality changes
• drowsiness or confusion
• loss of memory or concentration.

About the Author

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