Stereotactic Radiation Therapy
A specialized type of external beam radiation therapy calledstereotactic radiation uses focused radiation beams targeting a well-defined tumor, relying on detailed imaging, computerized three-dimensional treatment planning and precise treatment set-up to deliver the radiation dose with extreme accuracy (i.e., stereotactically).
There are two types of stereotactic radiation:
SRS/SBRT is best for very small tumors. Doctors use specialized scans to pinpoint exactly where within the body the tumor target is located. A customized holder may be used to keep the body perfectly still during treatment, or the treatment machine may have the ability to adjust for patient motion such as during breathing. These techniques allow doctors to give a high dose of radiation to the tumor in a short amount of time. SRS/SBRT is a type of external beam radiation therapy that can be completed in one to five days rather than over several weeks.
The advantage of SRS/SBRT is it delivers the right amount of radiation to the cancer in a shorter amount of time than traditional treatments. Plus the treatment is delivered with extreme accuracy, minimizing the effect on nearby organs. A disadvantage to SRS/SBRT is that this technique is suitable only for small, well-defined tumors that can be seen on imaging such as CT or MR scans, thus the approach is not suitable for all situations. Also, the amount of radiation that may be safely delivered may be limited if the cancer is located close to a sensitive normal structure, such as the spinal cord or bowel. You may want to read ASTRO's Emerging Technology Committee's report on SBRT for prostate cancer.
Other Names for Stereotactic Radiation
There is sometimes confusion about the branding of equipment separate from the terminology of SRS or SBRT. Stereotactic radiation may be delivered by a number of different devices; brand name stereotactic treatment machines you may hear mentioned include: Axesse, CyberKnife, Gamma Knife, Novalis, Primatom, Synergy, X-Knife, TomoTherapy or Trilogy. It is important not to confuse these brand names with the actual type of stereotactic radiation under consideration.
How Are These Treatments Alike?
- Use multiple narrow radiation beams.
- Target small, well-defined areas with precision.
- Use immobilization devices or techniques that limit monitor and adjust for any movement during treatment.
- Give high doses of radiation safely and accurately over just a few treatments (usually one to five sessions overall).
How Are These Treatments Different?
- Different capabilities: Some stereotactic systems can treat only tumors in the head, others in the head and neck, and others anywhere in the body.
- Different schedules: Some stereotactic treatments may be best given in a single session, others may be given in a few treatments over several days.
- Different ways to achieve accuracy: Different systems use different ways to keep patients in the correct position. Some use customized holders that keep the patient immobile, and others have the machine track any movement of the patient.
Conditions Treated With Stereotactic Radiation
Stereotactic radiosurgery (SRS) is used to treat conditions involving the brain or spine including:
- Cancers that start in the brain (gliomas and other primary brain tumors).
- Cancers that spread to the brain (brain metastases).
- Benign tumors arising from the membranes covering the brain (meningiomas).
- Benign tumors of the inner ear (acoustic neuromas).
- Abnormal blood vessels in the brain (arteriovenous malformations).
Stereotactic body radiation therapy (SBRT) is used to treat small tumors in the chest, abdomen or pelvis that cannot be removed surgically or treated with conventional radiation therapy, including:
- Small lung cancers.
- Cancers that started elsewhere and spread to the lung (lung metastases).
- Cancers that started elsewhere and spread to the liver (liver metastases).
These lists cover commonly treated conditions but cannot include every possibility. Stereotactic radiation may be useful for other cancers not readily addressed with surgery or conventional radiation therapy. Patients with tumors that are small and few in number are the best candidates for stereotactic techniques. Not all patients can benefit from this type of treatment.
Your radiation oncologist can tell you whether this approach is an options for your specific condition as new research continues to broaden the use of this technology.
Who Is Qualified to Provide Radiation Therapy?
Radiation oncologists are highly trained, board-certified and licensed physicians who use radiation therapy in its various forms to care for patients with cancer and other conditions, and who oversee the care of each person undergoing stereotactic radiation. Radiation oncologists team up with neurosurgeons for stereotactic radiosurgery of the brain or spine.
Other members of the radiation therapy treatment team include medical physicists, dosimetrists,radiation therapists and radiation oncology nurses.
Where Should I Be Treated?
Modern radiation therapy facilities are widely available across the country. Not all of them offer every type of radiation treatment. You should choose a center that offers the most appropriate treatments for your particular condition. Possibilities include:
- Academic medical centers located at major universities across the country.
- Community hospital cancer centers.
- Freestanding radiation therapy or cancer centers.
The suitability of a given treatment center will depend on the specific treatment you require, the technical capabilities of the center, the experience of the physicians and the center's location. Your health insurance plan may limit your choices to certain preferred centers.
How Do I Choose the Best Treatment For Me?
Choosing between treatments is confusing, and sometimes there is no simple answer. For many patients, there are several reasonable options. Factors to consider:
- Is reliable medical evidence available supporting the use of this treatment for your specific condition? This evidence may be hard to find for some new technologies.
- What are the side effects?
- Is it covered by insurance?
- Is travel required to get to the treatment?
- Have you had the opportunity to ask questions and had them answered to your satisfaction?
- Do you feel comfortable with the radiation oncologist?
Things You Should Know
- Your physician should discuss all of the appropriate, medically approved treatments related to your condition. Be concerned if your doctor refuses to talk about other treatments.
- Question heavily advertised treatments that are not backed by scientific evidence.
- You can always seek a second opinion. No doctor should discourage you from getting one.