Brain Tumor Surgery and Radiation

by Food and Drug Administration (FDA)

(Page 2 of 3)

Devices Revolutionize

The neurological examination is one of the most helpful tools in the diagnosis of brain tumors. The neurologist checks eye movement, eye reflexes and pupil reaction, hearing, reflexes, sensation, movement, and balance and coordination.

Some laboratory tests, such as the electroencephalogram (EEG), are also useful in diagnosis. The EEG uses special patches placed on the scalp to record electrical currents. Certain patterns in the brain's electrical activity may suggest a local abnormality. Further investigation may turn up a tumor, stroke or other disorder.

For years, doctors diagnosed brain tumors with a technique called angiography. A series of x-ray images is made of the brain after a "dye" (a radiographic contrast material opaque to x-rays) is injected into a major blood vessel. The pictures make the brain's blood vessels visible.

If angiography is not much used today, it's because the diagnosis of brain tumors has been revolutionized in the last two decades by the development of special imaging techniques, such as computed tomography, or CAT scan. This test is especially useful in showing the tumor's location. A CAT scan is made by sending x-rays through the body at various angles and then assembling these images by computer to give cross-sectional views. This test is often used with contrast material injected into the patient. The dye helps outline certain parts of the brain and sometimes makes it easier for the doctor to see abnormal tissue, such as tumors.

Magnetic resonance imaging, or MRI, does not use x-rays, but rather subjects tissues to a strong, but harmless and painless, magnetic field. Unlike the CAT scan, which produces an image that depends on x-ray absorption, MRI produces an image that reflects magnetic properties of the body. One advantage of MRI is that the examination can be tailored to highlight different types of diseases. MRI used in conjunction with contrast materials containing magnetic substances (unlike those used in CAT scans) has been found to be very effective in imaging brain tumors.

Positron emission tomography (PET) is used less often than either CAT scanning or MRI because the equipment is more expensive. PET measures the brain's activity using positron-emitting radiopharmaceuticals, which are injected into the patient before the test. PET scans can be especially useful in detecting recurrent tumors.

To make a definitive diagnosis, doctors often take a small amount of tissue from a suspected tumor, which a pathologist examines under a microscope. This technique, called a biopsy, can reveal whether the cells are benign or malignant and can identify the type of tumor (there are many different types).

Standard treatments for brain tumors include surgery, radiation therapy, chemotherapy, or a combination of these approaches. Many benign tumors are treated by surgery alone, resulting in a complete cure. A highly malignant tumor, such as glioblastoma multiforme, also called high-grade astrocytoma, may require all three types of treatment.

Surgery

The surgeon's aim is to remove the tumor completely without damaging normal brain tissue. To achieve this goal, a whole array of surgical tools has been developed in recent years.

Among the most important are exquisitely miniaturized devices such as the surgical microscope and microsurgical instruments, all regulated by FDA. Microsurgical techniques have made it possible for the neurosurgeon to remove tumors that were once considered inoperable.

"Surgical microscopes are continually being refined," says Steven Brem, M.D., Chief of Neurosurgery, at the H. Lee Moffitt Cancer Center, Tampa, Fla. "They're more flexible, more powerful, provide greater illumination, and are easier to use. They have definitely shortened surgical time." Magnification of the operating area has also made it easier for the surgeon to differentiate between tumor tissue and normal tissue.

Another tool used extensively by neurosurgeons is the ultrasonic aspirator, a device that uses high-frequency sound waves to break up tumors and an aspirator to "vacuum" tumor pieces. "The ultrasonic aspirator is a safe tool that has enabled the cure of benign tumors, especially those that are fibrous, or difficult to remove, or stuck to a nerve," says Brem.

Lasers release a beam of concentrated light energy that can destroy small areas of tumors and can help control bleeding. Those approved for use on brain tumors include carbon dioxide lasers and YAG lasers (Nd:YAG and frequency double Nd:YAG).

Radiation

Radiation therapy is the use of high-energy beams of either x-rays or gamma rays to stop cancer cells from growing and multiplying. Radiation is used after surgery when the surgeon has not been able to remove every bit of cancerous tissue, or is used instead of surgery when a tumor is in a brain area where removal would harm the patient. Certain drugs called radiosensitizers — HU (hydroxyurea), BUdR (bromodeoxyuridine), and IUdR (5-iodo-2-deoxyuridine) — are sometimes given during radiation therapy. These drugs are still being tested. It is hoped that they will make tumor cells more sensitive to radiation therapy.

Another type of radiation treatment currently being used is interstitial brachytherapy. Radioactive "seeds" are planted directly into the brain tumor where they can remain for a period of time. This technique is useful for treating small tumors that cannot be removed surgically.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.