Stereotactic Radiosurgery & Radiation Therapy 

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Radiation therapy, or radiotherapy, uses high-energy beams (X-rays or gamma rays, for example) to kill tumor cells and keep tumors from growing. Radiation can be targeted to reach the brain tumor without affecting other parts of the body, and may be used before, after or instead of surgery, depending on each patient’s situation. 


At Houston Methodist, we use the latest technology to selectively attack the tumor. Stereotactic radiosurgery (SRS) is the use of radiation therapy to manipulate and focus the beam to the precise shape of the tumor to minimize the amount of radiation passing through healthy brain tissue. In this case, the radiation is delivered from an external beam. Your doctor may also consider and discuss surgery and/or chemotherapy with you. 


Stereotactic Radiosurgery (SRS)

Many brain tumors that were previously considered untreatable can now be treated quickly, effectively and safely with radiosurgery. It is often a successful treatment option for people who have remaining lesions after surgery or for brain tumors that are in regions with critical functions or that are risky to access with conventional surgery. 


Our experts can treat both primary tumors (those that originate within the brain) and metastatic tumors (secondary tumors, or tumors that have spread from cancer sites outside the brain), usually with a single, one-day treatment, or in a short course of three to five treatments, instead of the usual 20 to 26 treatments required for radiation therapy.

Many patients originally thought to have inoperable tumors can now be safely and effectively treated. This technique has given patients new treatment options to avoid or augment surgery and minimize side effects from surgery or more extensive traditional radiation treatments. In some cases, patients who previously had limited life expectancy now have the potential of longer-term survival with enhanced quality of life.


Disorders treated with SRS include:

  • Acoustic neuroma
  • Arteriovenous Malformations (AVMs), Dural AV Fistulas
  • Brain metastases 
  • Functional disorders (movement disorders, e.g.)
  • Gliomas 
  • Meningiomas
  • Skull base tumors: Meningioma, schwannoma, chordoma, glomus tumors, adenoid cystic carcinoma, primary skull base carcinoma, esthesioneuroblastoma
  • Trigeminal neuralgia


Houston Methodist Hospital Radiosurgery Program 

Neurosurgeons and radiation oncologists at Houston Methodist Hospital Sterotactic Radiosurgery Program use highly specialized stereotactic radiosurgery equipment, such as the Gamma Knife and Novalis®, to focus beams of radiation only where needed to destroy cancerous or noncancerous growths without damaging healthy brain tissue. These beams are formed to the complex, 3-D shape of each person’s tumor, allowing physicians to administer higher doses of radiation more precisely and safely. That makes this noninvasive, nonsurgical treatment less toxic than previous radiation treatments for brain tumors.
Before treatment, patients will undergo 3-D magnetic resonance imaging (MRI) and computerized tomography (CT) to give physicians an accurate view of each patient’s internal anatomy and the shape and location of each tumor. Then radiation oncologists and neurosurgeons, together with the patient, develop a personalized treatment plan. 

More About Stereotactic Radiosurgery

Types of SRS

SRS can be delivered with the Elekta Gamma Knife (GK) or a LINAC based system (Novalis, Varian Edge). Both deliver a high dose of focused radiation to the target while minimizing doses delivered to adjacent normal structures. In each system, a pre-treatment imaging study with fixed markers is used to identify the precise coordinates or 3-D location of the target. This “map” provides a template on which the computer assisted treatment plan is then generated to precisely target your lesion. 

How does SRS work?

The doses delivered by SRS to the target volume produce cellular injuries, which either kill cells or render them “sterile” and incapable of further growth. This effectively treats tumors. SRS also generates a scar response in blood vessels, effectively eliminating blood flow and risk of bleeding when treating vascular malformations. 

What are the potential risks and side effects of SRS?

While radiation is extremely effective in treating a variety of lesions, it is rare that it permanently injures surrounding structures. The potential side effects from radiation depend on the specific functions in or around the area being treated. To distinguish radiation injury from disease progression, patients may undergo specialized imaging, such as a PET scan, or may be treated with medications to reduce swelling or improve blood flow. Your doctor will discuss all potential side effects and their treatments with you.

Your treatment

There are three essential steps to the SRS treatment process: pretreatment evaluation, treatment simulation and treatment itself. Your physician will walk you through the details of each step, making sure you understand what the treatment entails and are as comfortable as possible throughout the entire process.


The team will assess the effectiveness of your treatment through periodic evaluations and imaging. All patients are entered into a database, and imaging and clinical updates are periodically reviewed by the SRS Treatment Board to monitor response and side effects. Your referring physician will receive updates from these evaluations as part of your longer-term care. A clinical contact will be available for any questions you might have before and after your SRS treatment.

Stereotactic Radiation Therapy for Brain Tumors

If a brain tumor is located in an area that is especially sensitive to high doses of radiation, the radiation dose may be lowered and delivered over several days or weeks. This is called fractionated stereotactic radiation therapy. It allows radiation oncologists to effectively target tumor cells, while allowing surrounding healthy cells to recover between treatments. As with stereotactic radiosurgery, the doctors use MRI and CT scans to view the tumor and to plan treatment.

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