Stereotactic Radiation Therapy: Gamma Knife and CyberKnife
Stereotactic radiation therapy is a type of radiation that delivers a high dose of radiation to a small, well-defined area using precisely focused beams. This helps target the cancer without harming nearby healthy tissue. In breast cancer, stereotactic radiation is most often used to treat spots of metastatic disease in the brain, spine, bones, lungs, or liver. Stereotactic radiation is used when cancer is in a delicate area and doctors want to be sure the surrounding tissues are not harmed by radiation. It’s also used when surgery isn’t an option.
Stereotactic radiation therapy is also called:
stereotactic external beam radiation therapy
stereotaxic radiation therapy
stereotactic body radiotherapy
stereotactic radiosurgery
stereotactic ablative radiotherapy
It may also be referred to by the brand names Gamma Knife and CyberKnife. While the words “surgery” and “knife” are in some of the names for stereotactic radiation therapy, it’s not traditional surgery because there’s no incision.
Stereotactic radiation is a type of external beam radiation.
What’s the difference between Gamma Knife and CyberKnife?
Gamma Knife and CyberKnife are both types of stereotactic radiation. They differ in how the radiation is delivered, the source of the radiation energy, and how much you can move during treatment. CyberKnife is considered more comfortable than Gamma Knife, but Gamma Knife treatment is usually shorter — one day of treatment versus several weeks. Because the CyberKnife can be used to treat more areas of the body, there are more CyberKnife machines than Gamma Knife machines in the United States. Gamma Knife machines can only treat tumors in the brain, head, and neck (cervical spine).
During Gamma Knife treatment, you wear either a metal frame around your head and neck that’s attached to your skull with screws or a custom-fitted rigid mesh mask over your face. If your treatment uses the head frame, you usually receive local anesthesia to areas where the screws are placed. When treating cancer in the brain, precision is extremely important and the frame or mask ensures that your head doesn’t move during treatment. You usually have only one treatment session. Gamma Knife delivers multiple high-intensity radiation beams to one area. This treats cancer and doesn’t harm nearby healthy tissue.
During CyberKnife treatment, the radiation is delivered by a robot arm that can move around your body. The system tracks the position of the tumor as your body naturally moves, including during breathing, heartbeat, and digestion. Instead of a metal frame or rigid mask, CyberKnife uses a soft, flexible mask or body mold, so anesthesia isn’t needed. Because the robot arm can move, CyberKnife can deliver radiation to any area of the body from any angle. A full course of CyberKnife treatment usually takes one to five sessions spread out over several weeks.
Stereotactic radiation: What to expect
Treatment is often completed in one to five sessions. The planning and treatment process for stereotactic radiation therapy depends on whether you’re receiving stereotactic radiation from a Gamma Knife or Cyberknife machine. On the day of treatment, you should plan on having someone come with you to the clinic and drive you home after the procedure. You may have an IV inserted to give you fluids if you’re not allowed to eat or drink that day. Although you may feel some discomfort when the Gamma Knife head frame is placed, receiving the stereotactic radiation with either machine is painless.
What to expect with Gamma Knife treatment
Because Gamma Knife treatment requires a metal head frame or mask that must stay in place during imaging, planning, and treatment, the entire process happens on the same day.
Before treatment
It’s recommended that you wash your hair and scalp the night before treatment. You may be given a special shampoo to use. Wear your hair loose and don’t use any clips, pins, bands, hair spray, or other styling products.
Day of treatment
Wear slip-on shoes, loose fitting pants or shorts with an elastic waist, and a shirt that closes in the front, rather than a shirt that has to go over your head. If your treatment involves a head frame, you won’t be able to fit a shirt over your head once it’s in place.
Before the procedure starts, the metal frame is attached to your head with four screws. The shape of the frame may vary slightly depending on where you’re receiving treatment. But in general, it looks like a large metal circle that goes around your head just below your ears. Four rods stick up from the circle, two in the front and two in the back. The rods hold the screws that attach the frame to your scalp. You receive shots of numbing agent at the four places where the screws are placed: two points on your forehead and two at the back of your head. Your hair doesn’t have to be shaved. The frame is usually attached first thing in the morning on the day of your treatment.
When a mask is used instead, it’s molded to exactly fit your head and face. The mask is made of plastic material that looks like mesh that’s hard at first. It’s then placed in a warm water bath to make it flexible. After the mask comes out of the water, it’s gently stretched over your face and attached to the treatment table using clips. It feels warm and wet. Technicians use their fingers to mold the mask around your head, face, eyes, ears, and throat. The holes in the mesh make it easy for you to breathe and see. It takes about 10 minutes for the mask to cool and harden.
Since the process of securing the head frame or mask in place can be stressful for many people, you may be given medicine to help you relax before either procedure.
Breastcancer.org Community member @illimae had Gamma Knife treatment for brain metastases and shared their experience. “The procedure begins with the fitting of a metal head frame or a plastic mesh mask. The mask is initially soft and form-fitting, but hardens quickly for a secure fit and is claustrophobic for many. The metal head frame requires numbing medication injected into your head… where the frame’s pins will secure the frame to your skull. This process is the most anxiety-inducing and painful (due to the injections) part, so Xanax, Ativan or something similar is highly recommended, especially if you are needle-phobic."
After the frame or mask is in place, you have scans of the area to be treated — MRI or CT scans or both — so your doctor can see the exact location of the tumor. Depending on the type of scan, you may have dye injected into a vein in your arm.
The scan results are then fed into a computer that calculates the correct dose and helps your treatment team map out the precise treatment area. This planning process may take an hour or more. While that’s being done, you can relax in another room, but the frame or mask has to stay attached to your head or face.
During treatment, you lie on a bed that slides into the machine. The head frame or mask is attached to the bed to keep your head completely still. The machine doesn’t move during treatment. Instead, the bed moves inside the machine. The procedure can take from less than an hour to about four hours, depending on the size and shape of the treatment area. You’ll be alone in the room with the machine, but you can talk to the treatment team through a microphone.
After treatment
After treatment, the head frame or mask is removed. If the frame was used, you may have a little bleeding where the screws were attached, and the areas may be slightly tender. If you had an IV placed, it’s also removed. If you have a headache or feel sick to your stomach, tell your treatment team right away so they can give you medicine.
You’ll be monitored for about 30 minutes before going home. You can eat and drink normally afterward. It’s recommended that you have someone stay with you the night after treatment in case you have any side effects.
What to expect with CyberKnife treatment
CyberKnife treatment takes place over several weeks.
Before treatment
Before treatment starts, you have a planning session that starts with imaging, usually an MRI, CT, or PET scan, so your doctor can see the exact size, shape, and location of the tumor. With the help of a computer, your doctor uses your scans to calculate the correct dose of radiation and map out the treatment area.
Depending on the tumor’s location, you may need a minor procedure so your doctor can place tiny gold seeds in or near the tumor to track its position during treatment. You’ll also be fitted for a customized face mask made of soft mesh material or body cradle, also made of soft material, to keep you still during treatment. The mask or cradle isn’t attached to your body or the treatment table. They’re designed to hold you still and keep you in the same position for each treatment.
Day of treatment
About a week or two after the treatment planning session, you return to the center for treatment.
On the day of treatment, it’s recommended that you wear loose, comfortable clothes and slip-on shoes. You can eat and drink normally that day. You should avoid using any moisturizers, lotions, creams, powders, or deodorant on the treatment area for at least four hours before the procedure.
During treatment, you lie on a table, which automatically positions you. A computer moves the robot arm around your body to each pre-defined position, where it stops to precisely deliver each radiation dose. You don’t need anesthesia. Treatment generally lasts between 30 and 90 minutes, and you typically have one to five treatment sessions over one to two weeks.
After treatment
If you have a headache or feel sick to your stomach, your treatment team will give you medicine. Although you may feel well enough to drive yourself home, most clinics recommend that you have someone drive you, but no one needs to stay with you overnight..
Stereotactic radiation therapy side effects
In many cases, the side effects of stereotactic radiation therapy are milder than traditional external beam radiation therapy and usually get better a few weeks after treatment. There can be some long-term side effects, but they depend on the area receiving treatment. Because stereotactic radiation therapy for breast cancer is often given to the brain or spine, common side effects are:
hair loss and skin irritation at the treatment site
scalp tingling or irritation
When stereotactic radiation therapy is used to treat breast cancer in the brain, it may cause swelling at or near the treatment site. Your doctor may prescribe anti-inflammatory medicines, such as steroids, to prevent swelling or treat any symptoms that you have.