Stereotactic radiosurgery (SRS)
Stereotactic radiosurgery (SRS) is a precise, noninvasive medical procedure that utilizes multiple beams of radiation to target tumors, particularly those located in challenging areas such as the brain, chest, or abdomen. This technique is often employed for various types of tumors, including brain tumors like meningiomas, paragangliomas, and acoustic neuromas, as well as metastatic and other difficult-to-reach cancers. One of the key advantages of SRS is its ability to deliver high doses of radiation with remarkable accuracy, enabling treatment of tumors that may not be suitable for traditional surgery, while minimizing damage to surrounding healthy tissue.
Before the procedure, patient preparation can vary depending on the tumor's location and the technology used, which may involve the attachment of a halo frame or the use of a robotic linear accelerator. The procedure itself typically lasts from thirty minutes to two hours, during which patients remain awake and can communicate with the medical staff. While SRS may cause temporary side effects such as headaches or nausea, it generally allows for a quicker recovery compared to conventional surgery, with many patients returning home within hours.
Post-treatment, the effectiveness of SRS is monitored over time, as tumor shrinkage occurs gradually. Advances in imaging and treatment delivery continue to enhance the precision and efficacy of SRS, making it a valuable option in modern oncology.
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Subject Terms
Stereotactic radiosurgery (SRS)
ALSO KNOWN AS: Fractionated stereotactic radiosurgery
DEFINITION: Stereotactic radiosurgery (SRS) is a noninvasive procedure that uses multiple beams of radiation to treat a selected target, such as a brain tumor or a difficult-to-reach tumor in the chest or abdomen. The radiation comes from either cobalt or a linear accelerator.
Cancers treated: B and brain tumors (such as meningioma, paraganglioma, hemangioblastoma and craniopharyngioma), acoustic neuroma, metastases, head and neck cancers, lung cancer, pancreatic cancer, gynecological cancers, liver cancer, spinal cancer, other cancers that are difficult to reach
Why performed: SRS is the most precise method of tumor targeting in radiation therapy interventions. While stereotactic radiosurgery is noninvasive and similar to radiation therapy, it is so accurate that it is considered surgical. Most often, SRS is used to reach tumors not candidates for surgery or near structures that a surgical approach could damage. SRS provides the option for an outpatient procedure rather than a traditional surgery that may require several days or weeks of hospitalization. Sometimes, SRS may be used when patients have had previous radiation.
Patient preparation: Stereotactic radiosurgery preparation depends on the site of the tumor and the type of equipment used. The traditional approach to SRS in the head uses a lightweight halo frame attached to the skull with four small screws and cobalt radiation beams for treatment. Another option for SRS is a robotically controlled linear accelerator that delivers multiple beams and uses various techniques to hold the patient still. A facial mask or a body frame is fitted for each patient when the robotically controlled linear accelerator is used. Since treatments may last thirty minutes to two hours, positioning devices help the patient lie still during the treatment.
A computed tomography (CT) scan with contrast dye, a magnetic resonance imaging (MRI) scan, or an angiogram, all very accurate procedures, may be done to determine the size and location of the tumor or blood vessels to be treated. If treatment is in the head, a neurosurgeon will work with a radiation oncologist to review the images and other patient data to determine the site to be treated. Other physician specialists and the radiation oncologist may be involved in planning the SRS treatment for other body sites. Information is loaded into a treatment-planning computer that calculates how much radiation the patient will receive and precisely where to direct the beams. The patient may receive a mild drug to be more comfortable during the treatment.
Steps of the procedure: For a stereotactic radiosurgery treatment of the head using a cobalt radiation source, the patient lies down on the treatment table, and the halo head frame is attached to the equipment, securing the position of the head to prevent movement that might cause the radiation beams to stray onto normal tissue. Up to 201 separate beams may be used to shape the treatment area. The treatment may last two to forty-five minutes during the session. There is no pain during the treatment.
For a stereotactic radiosurgery treatment using a robotically controlled linear accelerator, the patient lies down on the treatment table. The premade positioning devices are adjusted to hold the patient in one position for the treatment. One beam of radiation is used as the linear accelerator moves around the patient in a circle to shape the treatment area. A single treatment or a daily treatment of one or two sessions for five or more days may be used.
Regardless of the equipment, the patient is awake and can talk with the radiation therapy staff using an intercom. The staff watches the patient on closed-circuit television. The patient may hear noises from the equipment as adjustments of the beam are made to move around the tumor.
After the procedure: If a head frame was used, it is removed. Depending on the procedure and the site treated, the patient may be able to go home in just a few hours or may stay overnight in the hospital. The patient may need to lie still for a while after the procedure. The doctor will provide information about when the patient may resume normal activities, usually in just a few days. It is safe for patients to be around others, including children and pregnant women, because no radiation is in the body.
In the twenty-first century, advances continue to be made in stereotactic radiosurgery techniques. Proton beam therapy is a type of stereotactic surgery that can treat brain tumors in just one procedure, or can be employed to treat body tumors over several sessions. As imaging techniques advance, stereotactic radiosurgery has evolved to target tumors more precisely, allowing doctors to better understand their properties and adjust treatments accordingly. Additionally, various treatment delivery mechanisms have been developed, allowing doctors to effectively and accurately ascertain the correct radiation dosage.
Risks: Side effects depend on the site treated but may include headache, swelling as the tumor cells die, minor swelling where the head frame was attached to the skin, nausea, skin irritation, diarrhea, or bladder problems. There is a slight chance of paralysis or other deficits, such as weakness or difficulty with speech or hearing, when the brain or spine receives radiation.
Results: Stereotactic radiosurgery does not work immediately but causes cell death over time. The tumor decreases in size over time based on the type of tumor and its growth rate before treatment. Malignant tumors and metastatic tumors usually respond more rapidly because their growth rate is faster. The patient sees the physician frequently to monitor the tumor destruction and to be sure that side effects are not developing as the cells die.
Bibliography
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