Why Am I Hearing So Much About CyberKnife?

Radiation oncologist and CyberKnife expert Abraham Wu

Radiation oncologist Abraham Wu explains that CyberKnife is a brand name for one of several available stereotactic radiosurgery devices.

Note: This article was updated in November 2018.

Advertisements for a radiation delivery system called CyberKnife® have prompted a large number of questions from patients inquiring whether it employs a unique new technology.

CyberKnife is used in a type of radiation therapy called stereotactic radiosurgery (also known as stereotactic radiotherapy). This treatment destroys tumors with extremely precise, very intense doses of radiation while minimizing damage to healthy tissue, offering accuracy akin to the sharpness of a surgeon’s scalpel.

Memorial Sloan Kettering radiation oncologist Abraham J. Wu employs stereotactic radiosurgery to treat lung and gastrointestinal cancers. He explains that CyberKnife is a brand name for one of several available stereotactic radiosurgery devices that deliver radiation with linear accelerators, or devices that form beams of fast-moving subatomic particles. The beams are precisely directed through the use of advanced imaging technologies combined with a sophisticated computer guidance system.

“There are a lot of different machines and a lot of different marketing terms thrown around, but they all achieve the same goal, which has two critical components,” Dr. Wu says. “One is delivering a more intense dose of radiation in just a few sessions. This is called hypofractionated radiation therapy. The other is targeting the radiation very accurately by pinpointing the precise location of the tumor during treatment.”

At MSK, radiation oncologists use linear accelerators made by a company called Varian. The Varian machine Dr. Wu most often uses — primarily to treat lung tumors — employs a system called TrueBeamTM, which incorporates computed tomography (CT) imaging into the same device that delivers the radiation. This allows the radiation therapists to make sure patients remain in the proper position during radiation therapy and to adjust the radiation beams as needed.

MSK Precise: Larger Doses over a Shorter Period

MSK Precise incorporates the TrueBeam system to deliver hypofractionated radiation therapy. With this treatment approach, a radiation beam can be very precisely targeted to a tumor. The total radiation treatment can be split into fewer sessions, using larger doses given over a shorter period.

“Really, the big breakthrough in recent years has been the advent of CT imagers on the treatment machine itself — as we have with the TrueBeam — which allows us to ensure the accuracy of radiotherapy treatments with the highest precision,” he says. “Interestingly, CyberKnife does not incorporate a CT imaging machine into the device — it uses a different system of image guidance.”

In addition to using CT imaging, MSK Precise also employs MRI in the treatment of some cancers, particularly prostate cancer. When MRI is used to plan the treatment, CT scans are not needed. MSK is the only institution in the world to routinely use MRI for hypofractionated radiation therapy.

The main distinguishing feature of CyberKnife is that the linear accelerator is mounted on a robotic arm. While this offers more flexibility and freedom of movement in how the radiation beam is delivered, Dr. Wu says that “in practice this is rarely something that is going to make a difference in how precisely we treat someone. We can still deliver the radiation to a given target.”

What is important, he explains, is the skill and experience of the radiation oncologists and medical physicists who define the radiation target.

“There are a lot of different technical solutions to achieve the kind of accuracy that you need to deliver very high doses of radiation — it’s a variety of different means to the same end,” Dr. Wu says. “We’re convinced that our Varian machines enable us to perform stereotactic radiosurgery at the highest level.”


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My daughter is having this procedure next month..

How is this different from proton therapy?

Brenda, thank you for your comment. We consulted with Dr. Wu who provides this response:

Proton therapy means that the radiation is being delivered in the form of protons, a different type of subatomic particle. Both CyberKnife and TrueBeam use x-ray (also known as photon) radiation, which is the most common and best-established way to deliver stereotactic radiotherapy. Protons can sometimes be used to deliver stereotactic radiotherapy, but protons currently are not compatible with the same kind of sophisticated image guidance used in TrueBeam.

My husband has mesothelioma and is going to do proton therapy at md Anderson. He is currently enrolled in a clinical trial with ur hospital. Is this type of technology better than proton?

Brenda, unfortunately, we cannot answer personal medical questions on our blog. Decisions about the best therapy and best technology are based on each individual case, and we suggest your husband consult with his physician on questions such as this.

Ok thanks is much for the work u all are doing. I am so encouraged to hear about all the new technologies. We will discuss this with our radiologist.

Can this type of procedure be used on pancreatic cancer tumors(IPMN)? Thank you.

Barbara, thank you for your comment. Stereotactic radiosurgery as described in this story has been used to treat pancreatic cancer. You can read a recent discussion of it here:


If you would like to make an appointment with a Memorial Sloan-Kettering physician, please call our Physician Referral Service at 800-525-2225 or go to http://www.mskcc.org/cancer-care/appointment.

How does this compare to IMRT and Neutron radiation?

Sylvia, thank you for your comment. We consulted with Dr. Wu and he responded:

We incorporate intensity-modulated radiation therapy (IMRT) into our stereotactic treatments. IMRT is a way of “shaping” the radiation dose in complex ways, while “stereotactic” means that the radiation dose/shape is delivered very precisely. So the two techniques are not mutually exclusive and we combine the two. Neutron radiation is very rarely used for any cancer nowadays, and is not used for stereotactic radiation as far as I know.

can this be used for multiple areas of metastatic prostate cancer disease?

Has this device been used on tumors in the brain?

Mary, yes the devices discussed in the story have been used to treat tumors in the brain, both primary tumors and brain metastases. You can learn more about this treatment here:


(scroll down to the section titled “Brain Metastasis: Single-Day High-Dose Radiation”)

We plan to have an updated blog story about this in a few weeks with more detail. Thank you for your comment.

Where can a patient find information about radiation scatter to the heart when undergoing radiation for left breast cancer?

Joan, thank you for your question about radiation treatment of breast cancer. To learn more about how Memorial Sloan-Kettering treats breast cancer, you can go to http://www.mskcc.org/cancer-care. For questions about breast cancer treatment, you also can call the National Cancer Institute’s Cancer Information Service at 800-4CANCER (800-422-6237). To learn more about the CIS, including Live Chat help and how to send them an email message, go to http://www.cancer.gov/aboutnci/cis/page3.

I have leiomyosarcoma, I am currently getting IMRT to the sacrum. I had a tumor removed from the sacrum. I had cyberknife last April to a tumor in the liver. It was successful and they said it was gone, however they saw an increase in size in Dec. I am receiving treatment at Sara Cannon in Nashville. Is there a better treatment? I have had several surgeries and now it is back in my lungs again. I need some help determining the best treatment.

Dear Brenda, we are sorry to hear that the cancer is back. Unfortunately, we cannot answer personal medical questions on the blog. If you would like to make an appointment for a consultation with one of our specialists who can provide a personalized assessment of your treatment options, please call our Physician Referral Service at 800-525-2225. Thank you for reaching out to us.

I had this type of procedure for an acoustic neuroma 5 years ago. At the time, not a lot of data was out there in regards to long term effects. Has more data surfaced since then?

Michele, thank you for your comment. We are looking into finding an expert who can provide a response for your particular question.

Michele, we consulted with MSK physician Josh Yamada, who responded:

There are several large patient series (University of Pittsburgh, and the UK series, for example) with long term follow up suggesting the radiosurgery for this type of tumor has an extremely low incidence of serious complications.

I have metastatic colon cancer and there are very small lesions on my lungs. ( a few cms and less) Is this type of treatment available to treat small lesions?

Susan, we passed your question on to Dr. Wu and he responded:

Yes, SRS is frequently used to treat metastatic lesions in the lungs and other organs. Usually it is only recommended when there are a limited number of lesions (~3 or less), and the lesions are relatively small (~5cm or less), but it is always on a case-by-case basis.

Thanks for the reply. This is food for thought when considering the future of my treatment. What is the recovery like from this treatment on the lungs?

Susan, who passed your question on to Dr. Wu, who responds:

Most patients do not have any noticeable impact from this treatment on the function of their lungs. Often, the only noticeable side effect from SRS to the lungs is fatigue. There is, however, a small risk of developing a lung complication that can affect your breathing, as well as other risks that would have to be discussed with the radiation oncologist.

I have a friend with SNUC. His first surgery was just over three years ago. He has undergone multiple rounds of chemo and radiation therapy (including proton radiation) since. The cancer has returned. Is it reasonable to believe that CyberKnife radiation could target this tumor in an effective way.

Dear Mark, we are sorry to hear about your friend. We are unable to answer personal medical questions on the blog. If he would like to make an appointment with one of our physicians for a more-personalized assessment and recommendation, please have him call our Physician Referral Service at 800-525-2225. Thank you for reaching out to us.

Can this procedure be used to aid in liver cancer stage 4?

David, thank you for your comment. We are looking into this and hope to be able to post a response soon.

David, we consulted with Dr. Wu who uses stereotactic body radiotherapy to treat cancer and this is his response. I hope this is helpful:

It depends on what you mean by stage 4 liver cancer. If you mean cancer originating elsewhere in the body that has metastasized to the liver, then SBRT can sometimes be used to treat those liver tumors, but only in specific situations that you should talk to your doctor about. Likewise, SBRT can also sometimes be used to treat cancers originating in the liver, but whether this is technically possible or medically beneficial needs to be discussed with a doctor who knows the particular situation.

Thank you very much. Looking forward to your response.

My husband had a malignant brain tumor (oligodendroglioma) the size of a golf ball removed in 2000 and had radiation a year after. They now see signs of cell growth (?) and he will have three days of cyberknife treatment. He is asking if there are any side effects after this treatment?

Dear Denise, we are sorry to hear about your husband. We sent your inquiry to Dr. Kathyrn Beal, one of our radiation oncologists specializing in treating brain cancer, and she responded: “Cyberknife is a form of stereotactic radiosurgery and it is usually very well tolerated. Long-term there is a risk of radionecrosis (scarring of the normal brain tissue from the high doses of radiation). Radionecrosis typically occurs about 6 months to 1 to 2 years following stereotactic radiosurgery and occurs in roughly 10% of patients. You should inquire with his doctor about this.”

Thank you for reaching out to us.

Thank you for this information. I appreciate it.

Thanks radio department.
What is the utility of either Cyberknife or Truebeam in the management of cerebellar AVMs?

David, we are looking into an answer to your question and hope to post a response in the next few days. Thank you for your comment.

David, we passed your question on to Dr. Kathryn Beal, who responded:

Cyberknife or Truebeam stereotactic radiosurgery or gamma knife can all be used to treat AVM’s. We don’t treat AVM’s at our center since they are benign lesions and we treat primarily cancers or tumors here.

when the chemo can not stop the spread of cancer such as a lymphatic lung cancer is the cyberknife an option. Can a patient be receiving oxygen and be a candidate for the cyberknife

Dear Jero, thank you for your question. This type of radiation therapy can be given to patients with lung cancer that has spread to the lymph nodes. If you’d like to read more about radiation therapy for lung cancer, you can learn more here: http://www.mskcc.org/cancer-care/adult/lung/radiation-therapy. To make an appointment with one of our doctors, you can call 800-525-2225 during regular business hours, or you can go here to get more information about making an appointment: http://www.mskcc.org/cancer-care/appointment.

Would the cyberknife be affective for a tumor which is on the vagus nerve and twining near the vocal cords and carotid artery?

Dear Chris, thank you for your question. We reached out to Abraham Wu, who said: “This is an unusual situation which could only be answered by a radiation oncologist familiar with the details of your case. SBRT can technically be delivered to that region of the body, but whether this would be safe or offer you any potential benefit would have to be assessed by your doctor.”

Is SBRT/TrueBeam for NSCLC available only at the main campus, or is available in either of the Westchester offices? We live in Dutchess County.

Herschel, thank you for reaching out. Yes, SBRT is available at MSK’s Sleepy Hollow location and will be available at the Harrison site when it opens this fall.

Thank you for the prompt response. One quick follow up. Is there a difference between the TrueBeam technology used in Manhattan vs another SBRT modality used in Westchester. Is it worth the trip for an isolated lung lesion in a Stage IV NSCLC with a complex history, but an outstanding and unusual clinical
course (off chemo X 16 mo close to 4 yr survival good activity and living, very slow progression of remaining primary.

Dr. Lessin, we consulted with radiation oncologist Abraham Wu, who responds:

Sleepy Hollow does not have a TrueBeam, but the Harrison site will. In any case, TrueBeam is not required to give SBRT and in most situations our SBRT technique would be identical with or without a TrueBeam. 

Hello my mom was diagnosed with Stage 4 bladder cancer that has moved to her kidney, liver and maybe her lungs. Is SBRT something she can benefit from? Her oncologist said radiation wouldn't help her, but is it possible to do SBRT and chemo?

Dear Sally, we are sorry to hear about your mom. We cannot answer personal medical questions like this on our blog. If she would like to meet with one of our specialists to discuss whether SBRT would be a treatment option for her, please call our Physician Referral Service at 800-525-2225. Thank you for reaching out to us.

I have received proton beam radiation 11 years ago for a calcified chondrosarcoma at the base of my skull. Prior to that, I had 3 craniotomies, none of which offered much help. While it has not grown in any significant way since the proton beam, I am always looking for a way to be rid of it. In such a sensitive area, near the carotid artery, pituitary gland, and various nerves, could this be what I'm looking for?

Dear Cavan, thanks so much for your question. Stereotactic radiation therapy could be an option for someone with your type of cancer, but an expert would need to evaluate you in order to confirm that. For information about making an appointment with an MSK doctor, go to: http://www.mskcc.org/cancer-care/appointment. We wish you the best, and thanks again for reaching out.

How is Cyberknife different from Image-Guided Radiation?