Stereotactic Radiotherapy (SRS)

Written by Dr. Heinzerling

Stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT) are specialized techniques for treating small tumors in the brain, lung, spine, abdomen, liver, kidney, or bone with highly targeted, high-dose radiation therapy. The distinction between the two techniques lies in the number of treatments and the location of the body being treated. SRS typically involves a single treatment or “fraction” of radiation and is often directed towards the brain or spine. SBRT typically involves more than one fraction of radiation and may be targeted to other areas of the body like the lung or abdomen. These techniques may also be referred to as stereotactic ablative radiotherapy (SABR). These treatments utilize precisely delivered radiation beams to treat very specific areas.

Since the treatment is so precise, stereotactic techniques allow oncologists to better spare surrounding normal tissues than with conventional external beam therapy. Stereotactic radiotherapy also requires fewer sessions than other traditional radiation therapies.

The physicians of SERO were some of the earliest adopters of this advanced technology, so we are experts on the science behind and application of SRS and SBRT. As you consider your next steps in cancer treatment, your SERO cancer care team is here to answer any questions you may have about the techniques.

This page will help you to understand and navigate SRS or SBRT as a treatment option.

Stereotactic radiotherapy is an advanced form of therapeutic radiation. It is known as stereotactic radiosurgery when treating the brain and stereotactic radiotherapy, stereotactic body radiotherapy (SBRT), or stereotactic ablative radiotherapy (SABR) when treating the areas of the body.

These techniques utilize external beam radiation to precisely focus beams of radiation at small tumors. The treatment destroys certain types of tumors in the brain and other organs, including the lung, spine, liver, kidney, and bone.

Stereotactic radiosurgery originally evolved as an alternative to brain surgery. Where brain surgery is invasive, stereotactic radiotherapy does not require any incision or surgery. Instead, SRS delivers radiation beams through the skin to effectively decrease or eradicate cancerous cells.

Stereotactic radiosurgery is now a preferred treatment for many small tumors in the brain and spine because it is non-invasive and efficient. Most treatments for the brain or spine only require one session. Treatments for other areas, like the lung or liver, require only three to five sessions.

Many oncologists also recommend stereotactic radiotherapy because it is very precise. With acute radiation rays directed specifically at the small tumors, this treatment avoids affecting the surrounding tissues. This, in turn, lessens the negative side effects associated with other radiation therapies.

Finally, SRS is ideal for tumors that are difficult to reach through other treatment methods, especially those in the spine or brain.

Stereotactic radiotherapy utilizes multiple precise radiation beams to treat tumors. Like with other radiation treatments, these radiation beams damage the DNA of the cancer cells. This causes the cancer cells to die, which in turn causes the tumor to shrink.

Although it is sometimes referred to as stereotactic radio surgery, it is not really surgery and there are no incisions. SRS uses 3D imaging, like a CT or MRI, to map the tumor. Then radiation beams are delivered through the skin to the tumor.

The machines that deliver SRS use many high-energy beams. One of these beams would have little effect on the tumor. Cumulatively, however, they can destroy a cancerous tumor.

Radiation oncologists use one of three different technologies to deliver these radiation beams to patients:

Stereotactic radiosurgery treats cancers in the brain, while stereotactic body radiotherapy treats tumors in other organs or areas of the body.

This is often the preferred method for small tumors, especially those that are in hard-to-reach areas. It is also ideal for tumors that are near vital organs or anatomical regions more susceptible to radiation damage because its precision usually spares the surrounding area from side effects.

Since SRS and SBRT are delivered in one to five sessions, it’s also the preferred treatment option for tumors in places that might move or change positions.

Stereotactic radiosurgery is used to treat a variety of brain tumors, including:

• Benign tumors
• Malignant tumors
• Primary tumors
• Metastatic tumors
• Intracranial tumors
• Orbital tumors
• Base-of-skull tumors
• Tumor cells that remain after surgery

Stereotactic body radiotherapy can treat tumors in many other areas of the body through three to five sessions, such as:

• Lung cancer
• Liver cancer
• Pancreatic cancer
• Kidney cancer
• Spine cancer
• Bone cancer
• Prostate cancer
• Head and neck cancer

Both SRS and SBRT are typically performed as outpatient procedures. While few sessions are required for these treatments, each session may span over a full day. Therefore, we usually recommend a friend or family member accompany patients to their sessions in order to help with transportation and support.

In advance of your procedure, your cancer care team will spend time planning your treatment. This ensures that the radiation is delivered precisely and accurately during your treatment. This planning usually occurs on a day preceding your treatment.

Like with stereotactic radiosurgery, your cancer care team will need to plan your stereotactic radiotherapy before administering treatment. This could include:

Whether you undergo SRS or SBRT, you will not feel the radiation as it enters your body. In order to help you relax, you may be given a mild sedative, but you will be awake throughout the procedure. You will also be able to communicate with your doctor.

During a Gamma Knife procedure, you’ll be secured to a bed that enters a machine. Your head will also be secured within your head frame. The bed will move throughout the procedure, which may take one to four hours.

During a LINAC procedure, the machine will rotate around while the treatment table stays fixed. After the procedure, you may feel dizzy or nauseous, but you will be able to eat and drink.

Before your procedure, you should follow the instructions of your cancer care team, which may vary depending on your cancer. However, most radiation oncologists will ask the following:

• Wear comfortable clothing during your procedure. Do not wear jewelry, makeup or nail polish, glasses or contacts, dentures, or wigs.
• Communicate with your doctor regarding any medications you’re taking before your procedure. He or she will recommend whether or not to take the medications leading up to your treatment

One of the greatest advantages of SRS and SBRT is that these procedures are precise enough to avoid affecting the surrounding tissues. This alleviates many of the symptoms associated with radiation.

Some patients may experience short-term side effects during the weeks following their treatment, including:

• Fatigue
• Soreness and swelling
• Headache
• Nausea
• Vomiting
• Diarrhea
• Scalp irritation or sensitivity
• Hair loss
• Difficulty eating or swallowing

Rarely, patients may experience other long-term side effects. These usually manifest months or even years after treatment and may be permanent. These include:

• Brain or neurological problems
• Infertility
• Joint pain
• Changes to the lungs, kidneys, spine, or colon
• Fractured bones
• Difficulties swallowing or eating
• Lymphedema