Stereotactic Radiation Therapy

A specialized type of external beam radiation therapy called stereotactic radiation uses focused radiation beams targeting a well-defined tumor. It relies on detailed imaging, computerized three-dimensional treatment planning and precise treatment set-up to deliver the radiation dose with extreme accuracy. There are two types of stereotactic radiation:

1. Stereotactic radiosurgery (SRS) delivers one to five stereotactic radiation treatments to the brain or spine. SRS is delivered by a team involving a radiation oncologist and a neurosurgeon. This treatment does not involve surgery. An incision is not made and tissue is not surgically removed.
2. Stereotactic body radiation therapy (SBRT) or stereotactic ablative radiotherapy (SABR) delivers one to five stereotactic radiation treatments to tumors within the body, excluding the brain or spine.

SRS/SBRT/SABR is generally best for very small tumors. Doctors use specialized scans to pinpoint exactly where the tumor target is located. A customized holder may be used to keep the body perfectly still during treatment. Some treatment machines 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/SABR is a type of external beam radiation therapy that can be completed in one to five treatments.

The advantage of SRS/SBRT/SABR 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 other nearby organs.

A disadvantage of SRS/SBRT/SABR 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 this 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.

Other Names for Stereotactic Radiation

There is sometimes confusion about the branding of equipment separate from the terminology of SRS or SBRT/SABR. 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, Edge, Novalis, Primatom, Synergy, X-Knife, TomoTherapy, Trilogy, Truebeam, Versa HD or View Ray. It is important not to confuse these brand names with the actual type of stereotactic radiation under consideration.

How are these Treatment Systems Alike?

• Use multiple narrow radiation beams.
• Target small, well-defined areas with precision.
• Use immobilization devices or techniques that limit or 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 Treatment Systems 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 recur 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 pituitary (pituitary adenoma).
• Benign tumors of the inner ear (acoustic neuromas and vestibular schwannoma).
• Benign conditions of the cranial nerves (trigeminal neuralgia).
• 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 start in or 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 option for your specific condition as new research continues to broaden the use of this technology.

Who is Qualified to Provide Stereotactic Radiotherapy?

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.