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Radiosurgery Program

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Stereotactic radiosurgery delivers a single high dose of radiation to a three-dimensional lesion in the brain identified with CT scan or MRI. The position of the lesion identified using a head frame with a coordinate system and a sophisticated computer. The dose of radiation generally is lethal to the targeted tissue and, even though the radiation is focused very precisely on the target, some of the surrounding tissue will also receive some radiation. Therefore, in order to minimize the amount of toxicity to the healthy tissue, the size of the lesion treated must be less than 3 cm. (1 and 1/4 inch) in diameter.

Technical considerations
Stereotactic radiosurgery may be delivered through different technologies, each of which uses a different radiation source. The options (in no special order) include:

• Proton beams formed by a cyclotron. Only a few sites in the United States have this technology.
• Gamma rays produced by cobalt sources in a Gamma knife. A Gamma knife can only be used to treat brain lesions.
• X-rays delivered by a linear accelerator. These machines are also used for conventional radiation to the brain or other body sites.

Each system is used in conjunction with specialized computer programs. And patients respond to each type of radiation in about the same way.

Radiosurgery at University of Missouri Health Care is based on treatment with x-ray radiation via a linear accelerator, which is located at Ellis Fischel Cancer Center. Two different treatment plans are available, based on the shape of the lesion being treated:

• For small sphere-shaped lesions, cone collimators (devices which focus the radiation beams,) are used with beams delivered in moving arcs with a circular target. Several arcs coming from different directions meet at the lesion to target the diseased tissue.
• Many brain lesions do not have spherical shapes. So, radiosurgery also may be given using a mini-multileaf collimator (MMLC) that enhances the degree of precision of treatment. The MMLC contains a series of sliding shields that move to shape the x-ray beam to conform to the shape of the lesion, even if the lesion has as irregular a shape as the state of Texas or California. Then, the lesion is treated by using a number of beams coming from different directions, all focused on the lesion. Each beam is shaped differently, as the shape of the lesion is different, depending on the direction of the beam. This technique allows 95 percent of the radiation to target the lesion, avoiding "hot" and "cold" spots.

Sequence of treatment

1. Pre-treatment evaluation
Patients who may be candidates for treatment with stereotactic radiosurgery are evaluated by neurosurgeon N. Scott Litofsky, MD, in one of the Neuro-Oncology Clinics located at University Hospital or at Ellis Fischel Cancer Center. If radiosurgery is thought to be appropriate, oncology radiologist Steven Westgate, MD, will also evaluate the patient before treatment. A planning MRI will be performed in advance of the treatment. Some patients will be started on anti-seizure medications about one week before treatment.

2. Day of treatment
On the day of treatment, the patient arrives at Ellis Fischel Cancer Center’s Ambulatory Infusion Unit about 6:30 a.m. A nurse starts an IV so that the patient can receive any needed medications. Then, the patient is connected to a monitor to keep track of blood pressure, heart rhythm and oxygen saturation in the blood. The patient received Oxygen to breath.

Once the patient is set, the patient is given sedative and pain medications in the IV to make the patient comfortable. The scalp is cleaned with a soap solution. Local anesthetic to numb the area is injected in the scalp at the four sites where the head ring pins will attach to the skull. The head ring is tightened into place. After the sedative/pain medication wears off and the patient is awake and alert, the monitoring connections and oxygen are removed.

The patient is taken to the CT scanner. The head ring is secured to the CT table and a CT scan of the head is obtained. The patient returns to the Ambulatory Infusion Unit to have  breakfast and relax, still wearing the head ring.

Meanwhile, the physicians fuse the CT scan with an MRI obtained previously. The lesions to be treated, as well as structures the radiation should avoid, are drawn on the computer images. The radiation physicist determines the appropriate X-ray beams to treat the abnormality while minimizing radiation injury to the surrounding normal brain. Working together, the neurosurgeon and radiation oncologist review the plan – making revisions, if needed – and determine the dose of radiation.

Once the plan is determined, the machines are checked for accuracy. The patient is brought to the radiation oncology linear accelerator and positioned with the head ring secured to the couch. The patient receives the radiation at the dose prescribed for each lesion. Once the treatment is completed, the head ring is removed. The patient is allowed to go home, usually tin the early afternoon depending on the level of complication of the treatment plan. Typically, the patient is given a prescription for a steroid pill (Decadron) for two days and a mild pain reliever

3. Follow-up care
Normally two weeks after treatment, patients return to the clinic to see Dr. Litofsky to ensure no problems have developed. However, most patients do not have problems. If anti-seizure medications were started in preparation for the treatment, they are stopped at this time. A follow-up MRI is scheduled for three to six months following treatment, depending on the type of abnormality being treated. Follow-up continues as needed to be sure the abnormal tissue has responded appropriately to treatment and no long-term difficulties have occurred.

Response to treatment
Different abnormalities have different responses to treatment:

• Metastatic tumors usually disappear over time, although some may remain present on imaging studies.
• Meningiomas and vestibular schwannomas usually do not increase in size and sometimes they may shrink.
• Pituitary tumors and gliomas may shrink after treatment.
• Arteriovenous malformations should disappear, but it usually takes two years.

Potential side effects
Most patients have no difficulty with stereotactic radiosurgery. Several side effects may occur:

• Some patients may have fatigue after treatment. Usually, this symptom resolves after several weeks.
• Hair loss, which may be temporary or permanent, may occur.
• Injury to surrounding nerves or the brain is an uncommon occurrence.