Radiosurgery (CyberKnife)

Tumors are often treated with some form of radiation, either as a separate treatment or in conjunction with surgery, medication, and other remedies. Acoustic neuromas and skull base tumors are sometimes treated with stereotactic radiosurgery (SRS).

• Also referred to as radiosurgery, SRS targets tumors from several different angles with single, high doses of radiation during a single session.
• The beams are delivered in a way that protects surrounding tissue as much as possible

Stereotactic radiation is often recommended for patients 65 and older with tumors less than 3 centimeters. Radiosurgery can also be safely used on patients with underlying health issues such as heart disease. Younger patients may also benefit from SRS. Radiosurgery involves three different possible techniques:

• CyberKnife
• Gamma Knife
• Linear accelerator (older method not commonly used)

Patients often enjoy a more comfortable and noninvasive experience when the CyberKnife system is used for the treatment of acoustic neuromas. During the procedure, a lightweight and open-mesh face mask is usually worn. The robotic arm that’s part of the device is able to precisely direct radiation to the identified location of the tumor. Because of the specific focus of the radiation, other areas of the brain are protected.

Performed without anesthesia as an outpatient procedure, CyberKnife treatment requires one to five treatment sessions lasting from 60-90 minutes each for most tumors. The robotic arm used to deliver the radiation does not touch the patient. During the treatment, the patient will rest on a treatment table. The arm will be manipulated to move around the patient. Benefits for patients include:

• No pain during the treatment
• No incision, blood loss, or recovery time
• Very little risk of complications
• No head or body frame required during the procedure

When the Gamma Knife system is used for radiosurgery, the device will come into contact with the patient. Because there is patient contact, local anesthesia will be necessary. The radiation is delivered through a head-frame that will be placed on the head of the patient and secured in place.

Radiation can be delivered through approximately 200 sources when the Gamma Knife system is used. An MRI scan will be done to determine the exact location of the tumor. Similar to the CyberKnife, Gamma Knife can be very precise with the areas targeted while protecting other tissues.

A CyberKnife or a Gamma Knife device can be used to perform fractionated stereotactic radiotherapy. With this technique, radiation is delivered to the affected area with multiple (fractionated) doses over time instead of in a single, large dose. Fractionated SRS is especially well-suited to treat tumors located at the base of the skull, particularly those less than 3 centimeters in size.

Brain tissue and nerves in the head can often tolerate smaller doses of radiation better than a larger does delivered during a single session. There’s also less of a chance that nerves responsible for facial sensations and motor functions like chewing and biting (trigeminal nerves) will be damaged. Patients may need three to five doses with fractionated stereotactic radiotherapy to completely treat the affected area.

Radiosurgery is not “surgery” in the traditional sense. No incisions are necessary, so it’s considered a non-invasive procedure, even though internal structures will be targeted. It can be used to treat both benign (non-cancerous) and malignant (cancerous) growths. Radiosurgery typically involves 3-D imaging to increase the precision and accuracy of how radiation is delivered to the affected area.

Specifically, it works by targeting the DNA of cells within the tumor. The radiation damages cells so they can no longer reproduce. As a result of this damage to cells, the tumor shrinks, which reduces the risk that nearby nerves will be compressed by the growth. A newer form of radiosurgery involves the use of a proton beam. This type of radiosurgery can also be administered in single or multiple doses.

Whether or not radiosurgery is appropriate for a skull base tumor or an acoustic neuroma will depend on where it’s located, it’s size, and whether or not other treatments, including surgery, may be considered too risky. Due to the precision that’s possible with radiosurgery, it sometimes provides a treatment option for patients with tumors that cannot be safely reached or removed with surgery. Hearing is more likely to be preserved with the fractionated approach to radiosurgery.