Stereotactic Radiation Therapy (SRT)

Stereotactic Radiation Therapy (SRT) is a type of external radiation therapy which uses special equipment to precisely position the patient in order to deliver radiation to a well-defined cancerous tumor. With SRT, the total dose of radiation is divided into several smaller doses given over several days. Stereotactic radiation therapy is typically used in an overall treatment plan to treat brain tumors and other brain disorders.

How Does SRT Work?

Like other forms of radiation therapy, stereotactic radiation therapy does not involve the removal of the tumor. Instead, SRT causes the tumor to shrink by causing sufficient damage to the cells of the tumor to make them unable to grow. The damage accomplished through SRT procedures tends to produce results within a few months, indicated by shrinkage of the mass. 

SRT relies on thorough imaging with three-dimensional digital treatment monitoring to deliver extremely accurate and precise radiation dosage. Imaging provides the precise size and shape of the tumor in order to pinpoint treatment. 

The main distinguishing feature of stereotactic radiotherapy treatment, from other types of external radiation therapy, is the division of the daily doses of radiation into fractions. The number of fractions used for a treatment program can vary from between 3 and 30 fractions, depending on the individual situation and circumstances of treatment.    

In addition to carefully calculated dosages and targeting, SRT often requires immobilization devices to assist in limiting, monitoring or adjusting for any patient movement during treatment. Immobilization of the head is done through the use of a mask, specifically formed to fit your head, which helps to position your head in the same precise location for each fraction. Other types of molds can be made to immobilize other body parts as well. This is critical to provide a higher level of accuracy without damaging nearby tissue.

Planning for SRT

Stereotactic Radiation Therapy does require planning for the patient is ready to begin treatments. During a planning appointment, a radiation specialist will take scans to determine:

  • How much radiation will need to be delivered to the tumor
  • The exact shape of the radiation beam to be used
  • Where exactly to send the radiation beams
  • What type of immobilization the treatment requires (head mask or frame, etc)
  • How many treatments are needed

After the patient’s planning appointment is complete, the Compass radiation experts will create the patient’s radiotherapy plan. This plan will be referred to each time the patient comes in for SRT treatment. 

Benefits of Stereotactic Radiation Therapy

  • Painless, non-invasive, and non-surgical
  • Ideal for well-defined small tumors, especially those that are close to critical organs
  • Can treat small tumors in the brain, that might otherwise be inoperable
  • Typically completed in two - eight treatments, in contrast to longer-term traditional radiation regimens
  • Treatments delivered with extreme accuracy, minimizing harmful side effects to nearby organs
  • Available as an outpatient option at various Compass locations

Examples of SRT Uses for Cancer Treatment

The treatment of brain tumors is the most common use of SRT. It is favored over whole brain radiation, because of its ability to target specific tumors without causing damage to surrounding brain tissue, and is especially effective in the treatment of metastasized brain tumors. SRT has also proven successful in treating other types of cancer, including:

  • Metastasized lung or liver tumors
  • Treatment of lung cancer in the early stages
  • Prostate cancer
  • Pancreatic cancer 
  • Spinal tumors
  • Benign inner ear tumors
  • Benign pituitary adenoma (pituitary tumors)

What are the Side Effects of Stereotactic Radiation Therapy?

The side effects that patient’s may experience depend upon which area of your brain has been treated, along with the amount of radiotherapy given during each dose. In most cases, patients will experience only some common, short-term side effects associated with SRT. 

Common SRT side effects during brain tumor treatments include: 

  • Nausea, Diarrhea, or Vomiting 
  • Vertigo or Dizziness
  • Headaches
  • Soreness from the head frame used to help to keep your head from moving during treatment
  • Fatigue
  • Skin Irritation - It is common for skin to become red, dry and irritated in the treated area, and the mask may leave temporary patterns on the skin.

Side effects of SRT are often mild and short-lived. However, in rare instances more severe neurological deficits can occur including seizures and speech, memory or reasoning issues. Some patients experience brain swelling. Sometimes, side effects appear months or even years after the SRS treatment ends.

If you experience any side effects after treatment be sure to advise your cancer care team. They have the necessary expertise to help patients deal with any of the symptoms and side effects related to your specific treatment plan.