Stereotactic radiosurgery

Stereotactic radiosurgery (SRS) uses many precisely focused radiation beams to treat tumors and other problems in the brain, neck, lungs, liver, spine and other parts of the body.

It is not surgery in the traditional sense because there’s no incision. Instead, stereotactic radiosurgery uses 3D imaging to target high doses of radiation to the affected area with minimal impact on the surrounding healthy tissue.

Like other forms of radiation, stereotactic radiosurgery works by damaging the DNA of the targeted cells. The affected cells then lose the ability to reproduce, which causes tumors to shrink.

Stereotactic radiosurgery of the brain and spine is typically completed in a single session. Body radiosurgery is used to treat lung, liver, adrenal and other soft tissue tumors, and treatment typically involves multiple (three to five) sessions.

When doctors use stereotactic radiosurgery to treat tumors in areas of the body other than the brain, it’s sometimes called stereotactic body radiotherapy (SBRT) or stereotactic ablative radiotherapy (SABR).

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.

How it works

  • All types of stereotactic radiosurgery and radiotherapy work in a similar manner.
  • The specialized equipment focuses many small beams of radiation on a tumor or other target. Each beam has very little effect on the tissue it passes through, but a targeted dose of radiation is delivered to the site where all the beams intersect.
  • The high dose of radiation delivered to the affected area causes tumors to shrink and blood vessels to close off over time following treatment, robbing the tumor of its blood supply.
  • The precision of stereotactic radiosurgery means there’s minimal damage to the healthy surrounding tissues. In most cases, radiosurgery has a lower risk of side effects compared with other types of traditional surgery or radiation therapy.

Indications: the use of stereotactic radiosurgery has expanded widely to treat a variety of neurological and other conditions, including:

  • Brain tumor.Stereotactic radiosurgery, such as Gamma Knife, is often used to treat noncancerous (benign) and cancerous (malignant) brain tumors, including meningioma, paraganglioma, hemangioblastoma and craniopharyngioma.

SRSmay also be used to treat cancers that have spread to the brain from other parts of the body (brain metastases).

  • Arteriovenous malformation (AVM).AVMs are abnormal tangles of arteries and veins in your brain. In an AVM, blood flows directly from your arteries to veins, bypassing smaller blood vessels (capillaries). AVMs may disrupt the normal flow of blood and lead to bleeding (hemorrhage) or stroke.

Stereotactic radiosurgery destroys the AVM and causes the affected blood vessels to close off over time.

  • Trigeminal neuralgia.Trigeminal neuralgia is a chronic pain disorder of one or both of the trigeminal nerves, which relay sensory information between your brain and areas of your forehead, cheek and lower jaw. This nerve disorder causes extreme facial pain that feels like an electric shock.

Stereotactic radiosurgery treatment for trigeminal neuralgia targets the nerve root to disrupt these pain signals.

  • Acoustic neuroma.An acoustic neuroma (vestibular schwannoma), is a noncancerous tumor that develops along the main balance and hearing nerve leading from your inner ear to your brain.

When the tumor puts pressure on the nerve, a person can experience hearing loss, dizziness, loss of balance and ringing in the ear (tinnitus). As the tumor grows, it can also put pressure on the nerves affecting sensations and muscle movement in the face.

Stereotactic radiosurgery may stop the growth or minimize the size of an acoustic neuroma with little risk of permanent nerve damage.

  • Pituitary tumors.Tumors of the bean-sized gland at the base of the brain (pituitary gland) can cause a variety of problems. The pituitary gland controls hormones in your body that control various functions, such as your stress response, metabolism, growth and sexual function.

Radiosurgery can be used to shrink the tumor and lessen the disruption of pituitary hormone regulation.

  • Stereotactic radiosurgery may be used to treat tremors associated with functional neurological disorders such as Parkinson’s disease and essential tremor.
  • Other cancers.SRS may be used to treat cancers of the liver, lung and spine.

Results

The treatment effect of stereotactic radiosurgery occurs gradually, depending on the condition being treated:

  • Benign tumors (including vestibular schwannoma).Following stereotactic radiosurgery, the tumor may shrink over a period of 18 months to two years, but the main goal of treatment for benign tumors is to prevent any future tumor growth.
  • Malignant tumors.Cancerous (malignant) tumors may shrink more rapidly, often within a few months.
  • Arteriovenous malformations (AVMs).The radiation therapy causes the abnormal blood vessels of brain AVMs to thicken and close off. This process may take two years or more.
  • Trigeminal neuralgia.SRS creates a lesion that blocks transmission of pain signals along the trigeminal nerve. Many people experience pain relief within several weeks, but it may take several months.