Stereotactic Radiosurgery

Stereotactic Radiosurgery

Stereotactic radiosurgery (SRS) is a non-surgical radiation therapy used to treat functional abnormalities and small tumors of the brain. It can deliver precisely-targeted radiation in fewer high-dose treatments than traditional therapy, which can help preserve healthy tissue.

Stereotactic radiosurgery (SRS) is a non-surgical radiation therapy used to treat functional abnormalities and small tumors of the brain. It can deliver precisely-targeted radiation in fewer high-dose treatments than traditional therapy, which can help preserve healthy tissue. When SRS is used to treat body tumors, it's called stereotactic body radiotherapy (SBRT).

SRS and SBRT are usually performed on an outpatient basis. Ask your doctor if you should plan to have someone drive you home afterward and whether you should refrain from eating or drinking or taking medication several hours before treatment. Tell your doctor if there's a possibility you are pregnant or if you're breastfeeding or if you're taking oral medication or insulin to control diabetes. Discuss whether you have an implanted medical device, claustrophobia or allergies to contrast materials.

Doctors use three types of technology to deliver radiation during stereotactic radiosurgery in the brain and other parts of the body:

• Linear accelerator(LINAC) machines use X-rays (photons) to treat cancerous and noncancerous abnormalities in the brain and other parts of the body. LINAC machines are also known by the brand name of the manufacturer, such as CyberKnife and TrueBeam. These machines can perform stereotactic radiosurgery (SRS) in a single session or over three to five sessions for larger tumors, which is called fractionated stereotactic radiotherapy.
• Gamma Knifemachines use 192 or 201 small beams of gamma rays to target and treat cancerous and noncancerous brain abnormalities. Gamma Knife machines are less common than LINAC machines and are used primarily for small to medium tumors and lesions in the brain associated with a variety of conditions.
• Proton beam therapy(charged particle radiosurgery) is the newest type of stereotactic radiosurgery and is available in only a few research centers in the U.S, although the number of centers offering proton beam therapy has greatly increased in the last few years. Proton beam therapy can treat brain cancers in a single session using stereotactic radiosurgery, or it can use fractionated stereotactic radiotherapy to treat body tumors over several sessions.

When you have stereotactic radiotherapy and radiosurgery

Stereotactic radiotherapy and radiosurgery isn’t suitable for everyone. You might have this type of treatment if you have a:

• vestibular schwannoma
• meningioma that started in the base of the skull
• pituitary gland tumour
• cancer that has spread to the brain from somewhere else in the body (secondary brain tumour)

Why is stereotactic radiosurgery performed?

SRS is a precise and powerful type of radiation therapy. SRS usually involves a single treatment of a very high dose of radiation in a focused location. Sometimes, it may involve a few treatments. During radiation therapy, your doctor uses radiation to damage the DNA of the tumor or other cells so that they no longer reproduce. This causes the tissue of the tumor to die.

SRS was originally developed to treat small, deep brain tumors. Now, it may be used for a wider array of problems in the brain and other parts of the body. Doctors use this method to treat areas that are hard to reach or close to vital organs, or they use it to treat tumors that have moved within the body. Examples of problems that your doctor can address with SRS include:

• deep brain tumors
• residual tumor cells after surgery
• pituitary tumors
• cancers of the eye
• arteriovenous malformations, which are tangled blood vessels that leak and disrupt your normal flow
• neurological problems, such as trigeminal neuralgia
• tumors in the lung, liver, abdomen, spine, prostate, head, and neck
• Parkinson’s disease
• epilepsy

Before the Procedure

Stereotactic radiosurgery takes a team approach, involving specialists in radiation oncology and neurosurgery. A dosimetry expert determines how the beams should be directed and a physicist calculates the amount of radiation the patient should receive, balancing risk and potential effectiveness. A key element of planning the procedure is maximizing the treatment to abnormal tissues, while protecting healthy tissues around the abnormal area.

Together, these experts spend about two weeks planning the procedure. The preparation time may be shorter in the case of an emergency.

Clothing and personal items

Wear comfortable, loosefitting clothing.

Avoid wearing the following items during SRS of the brain or spine:

• Jewelry
• Eyeglasses
• Contact lenses
• Makeup
• Nail polish
• Dentures
• Wigs or hairpieces

During the procedure

Children are often anesthetized for the imaging tests and during the radiosurgery. Adults are usually awake, but you may be given a mild sedative to help you relax.

If you are using a Gamma Knife machine, you'll lie on a bed that slides into the machine, and your head frame will be attached securely to the bed frame. The machine does not move during treatment; instead, the bed moves within the machine. The procedure may take less than an hour to about four hours, depending on the size and shape of the target. If treating with LINAC stereotactic radiosurgery of the brain the treatment will be quicker.

During the procedure:

• You won't feel the radiation.
• You'll be able to talk with the doctors via a microphone.

What you can expect

Stereotactic radiosurgery is usually an outpatient procedure, but the entire process will take most of a day. You may be advised to have a family member or friend who can be with you during the day and who can take you home.

You may have a tube that delivers fluids to your blood stream (intravenous, or IV, line) to keep you hydrated during the day if you are not allowed to eat or drink during the procedure. A needle at the end of the IV is placed in a vein, most likely in your arm.

Complications

Complications from radiosurgery are few — pin-site bleeding or infection is rare, and swelling around a tumor may occur, which is why Decadron is administered. In rare instances, a seizure may occur; these are generally brief and self-limiting. Caregivers or family members are asked to simply make sure the patient is safe, to call 911 with their physician’s information and to bring them to the hospital for further care. An anti-seizure medication is administered and is usually quite effective in controlling any further seizures.

One late complication that may be seen is known as radiation necrosis: tumor cells killed by radiation but inadequately cleared by the body. In some instances, this can cause further brain swelling requiring additional or increased dose Decadron. In refractory cases, hyperbaric oxygen may be administered, or surgery considered to remove dead tissue. This is why it is important to have close follow-up with a neurosurgeon or radiation oncologist.

It is also possible for a tumor to recur in a different part of the brain, as SRS only targets a very focal area; in such instances, the SRS treatment may be repeated on the new areas of tumor growth. Due to limitations imposed by overlap of radiation beams coming in from different directions, it is generally recommended to limit the number of tumors treated in one session to four. At times, a neurosurgeon and radiation oncologist will extend that number but only with careful consultation and consideration for the patient’s age, tumor type, location of the tumors in the brain and prior treatment history.

Possible Side Effects

Stereotactic radiosurgery causes fewer and milder side effects than conventional radiotherapies, which cover a wider area and can affect healthy tissue. The following side effects are typically temporary and get better within a few weeks.

• fatigue
• skin irritation at treatment site
• hair loss at treatment site
• headache
• neurological symptoms, such as seizure, numbness/tingling or weakness
• gastrointestinal symptoms, such as nausea, vomiting or diarrhea