Frequently Asked Questions

The CyberKnife System uses leading-edge robotics and advanced software technology, but it’s not new. The CyberKnife System has more than a decade of clinical evidence and has been used to help thousands of liver cancer patients. The CyberKnife System is used to treat liver cancers, with a procedure called stereotactic body radiation therapy (SBRT). It is an effective option for patients who cannot undergo surgery or radiofrequency ablation, and/or whose tumors cannot be completely removed with surgery. The CyberKnife System can also be used as a bridge to transplantation.1

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The FDA provided clearance for the CyberKnife System in 2001 for the treatment of tumors anywhere in the body, including the liver. The CyberKnife System is supported by years of published clinical follow-up with a large number of patients.

CyberKnife treatment is available at hundreds of locations worldwide.
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Treatment with the CyberKnife System is a non-surgical, outpatient procedure that does not require incisions or general anesthesia. Most patients will not require hospitalization or a long recovery period. The efficacy of the CyberKnife System for primary liver cancer is equivalent to surgery with milder adverse events.2

CyberKnife treatment eliminates the inconvenience and risk associated with the insertion of a needle-like probe into the tumor through the skin.

Radiation therapy is a treatment that uses high-energy X-rays (photons) to kill, shrink or control the growth of tumors. Radiation therapy works by damaging cells, disabling them from growing and dividing. The goal of any radiation treatment is to destroy cancer cells while minimizing the side effects on healthy tissue. As imaging technologies have improved over the last several decades, radiation therapy has integrated those improvements to enhance dose delivery and minimize side effects.

Radiation may be recommended as an alternative to surgery or in addition to other therapies. There are several kinds of radiation therapy. The CyberKnife System delivers a type of radiation therapy known as stereotactic body radiation therapy (SBRT).

Stereotactic body radiation therapy (SBRT) couples a high degree of targeting accuracy with very high doses of extremely precise, externally delivered radiation, thereby maximizing the cell-killing effect on the tumor(s) while minimizing radiation-related injury in adjacent normal tissues.

The hypofractionated, high-dose SBRT treatment delivered by the CyberKnife System has emerged as a ground-breaking treatment option — showing promising efficacy with low toxicity for primary liver cancer (e.g. hepatocellular carcinoma) and metastatic liver tumors.3, 4

Additionally, the CyberKnife System can also be used as a bridge to transplantation.1

There are numerous options for treating liver cancer, and the right option depends on your specific tumor location, cancer type and cancer aggressiveness — as well as your health, age and lifestyle. The CyberKnife System is an ideal treatment option for a wide range of cancer types and patient situations. The best way to determine if CyberKnife treatment is right for you is to find a CyberKnife treatment location and make an appointment to discuss your specific details.

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Despite the higher dose rate associated with SBRT, the efficacy of the CyberKnife System for primary liver cancer is equivalent to surgery with milder adverse events.2 The ability to adapt to motion and deliver precise doses of radiation enables clinicians to minimize radiation of healthy liver and surrounding organs at risk and to reduce toxicity.5 Most patients resume normal activity immediately after treatment sessions. Nonetheless, side effects can and do occur. Most radiation side effects are minimal and last only a short time. Side effects can, however, be severe.

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CyberKnife treatment is typically completed in just 1-5 sessions over 1-2 weeks.

Treatment sessions are non-invasive outpatient procedures, and no anesthesia is required. Most patients resume normal activity immediately after treatment sessions.

No anesthesia is required for CyberKnife treatment and treatment sessions are completed on an outpatient basis. Liver tumors will require the placement of fiducials within the organ. This procedure would be performed under local anesthesia.

The CyberKnife System was designed to provide the clinical team with a powerful tool to effectively control the cancer while minimizing side effects and the impact of treatment on patients’ daily lives. The majority of patients can continue normal activity during and immediately following CyberKnife treatment — compared to the typical requirement to limit normal activity several weeks after traditional surgery. In some circumstances, complications may occur.

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The CyberKnife robot, guided by motion synchronization software, can deliver radiation from virtually any angle — allowing it to maintain sub-millimeter accuracy throughout treatment delivery. Greater precision helps minimize dose to surrounding healthy tissues, preserving liver function and reducing the risk of side effects.

During treatment, a liver tumor will continuously move and deform throughout the course of treatment delivery.

Failing to adapt and synchronize the delivery of radiation dose with tumor movement can result in decreased dose delivered to the target — and increased dose delivered to healthy liver tissue and surrounding organs at risk. This can impact the overall effectiveness of the treatment and can potentially increase the incidence and severity of side effects — including reducing the liver’s ability to function.

Unlike any other radiation treatment, the CyberKnife System uses the world’s only real-time motion synchronization technology to continuously track that motion and adapt treatment delivery to maintain sub-millimeter precision. This ensures the radiation dose is delivered to the target — maximizing treatment effectiveness while minimizing dose to surrounding tissues to reduce the incidence of side effects. And unlike other radiotherapy options, the CyberKnife System does not require uncomfortable patient restraints or breath-hold techniques; you can relax and breathe normally, with full confidence in the CyberKnife’s synchronization capabilities.

Precisely delivering the prescribed radiation dose to the target is essential for reducing toxicity and preserving liver function.

Because many patients with liver cancers already have impaired liver function, minimizing damage to healthy liver cells is critical to preserving maximal liver function. Additionally, the liver is surrounded by sensitive organs and tissues, making precise delivery important for reducing the incidence and severity of side effects and protecting quality of life both during and after treatment.

SBRT is a form of hypofractionated radiation therapy. Hypofractionation entails delivering a higher dose per fraction across fewer total fractions. Hypofractionated radiation therapy, such as liver SBRT, has been proven to deliver clinical outcomes as good as surgery with milder adverse events2 — while dramatically reducing both the number of treatments and the total cost of care for both patients and payers.

Despite the higher dose rate associated with SBRT, multiple studies have validated that CyberKnife SBRT is well tolerated with minimal side effects. The ability to deliver precise doses of radiation enables clinicians to decrease exposure to surrounding healthy tissue and minimize side-effects that can reduce a patient’s quality of life. Most patients resume normal activity immediately after treatment sessions. Nonetheless, side effects can and do occur — and can be severe — with any treatment option, and should be discussed with your physician.

Compelling clinical evidence shows that the hypofractionated, high-dose radiosurgery delivered by the CyberKnife System can offer sustained tumor control with a low risk of serious toxicity and similar clinical outcomes to surgery with milder adverse events.2

  • A study of 75 patients with liver cancer treated using the CyberKnife System found that 89.8 percent of patients showed no progression of cancer beyond the liver two years following treatment. Overall survival at the one-year follow-up was 78.5 percent and at the two-year follow-up was 50.4 percent.6
  • A study evaluating the efficacy and toxicity of SBRT in the treatment of 57 patients with liver metastases showed more than 85 percent of patients achieved local tumor control at two years post treatment, without severe toxicities. Overall survival at the two-year follow-up was 55.9 percent. SBRT with the CyberKnife System is an effective alternative for those patients with liver metastases who cannot undergo surgery and/or whose tumors cannot be completely removed with surgery.4

Because the precise targeting of the CyberKnife System significantly reduces irradiation of liver healthy tissue and surrounding organs at risk, patients treated with CyberKnife are often excellent candidates for re-irradiation, in the event of recurrence.

Because the precise targeting of the CyberKnife System significantly reduces irradiation of liver healthy tissue and surrounding organs at risk, the CyberKnife System may provide a safe radiation treatment option even for patients who have previously received radiation therapy. Each patient should consult his or her physician regarding his or her own specific case.

As of January 2020, SBRT treatment for liver cancer is covered by Medicare in all 50 states and the District of Columbia. In addition, many private insurance payers cover SBRT treatment for liver cancer. It is always best to check your insurance policy and if applicable, be sure to review your employee contract to determine if your insurance coverage benefits are limited. If you live outside of the United States, typically the CyberKnife Center that you would choose for treatment can answer coverage questions.

Not every patient’s liver cancer is effectively treated with CyberKnife SBRT. Talk to your physician about your best options and come to a joint decision. Accuray’s Radixact® or TomoTherapy® System may be a good option to treat primary and metastatic liver cancer too. Radixact and the TomoTherapy Systems leverage CT-image guidance to ensure highly conformal dose delivery to the tumor with each treatment.


1 O’Connor JK et al. “Long-term outcomes of stereotactic body radiation therapy in the treatment of hepatocellular cancer as a bridge to transplantation.” Liver Transpl. 2012 Aug;18(8):949-54. doi: 10.1002/lt.23439.

2 Yuan Z et al. “Comparative research on the efficacy of CyberKnife® and surgical excision for Stage I hepatocellular carcinoma.” Onco Targets Ther. 2013 Oct 29;6:1527-32. doi: 10.2147/OTT.S51452. eCollection 2013.

3 Bibault JE et al. “Stereotactic body radiation therapy for hepatocellular carcinoma: prognostic factors of local control, overall survival, and toxicity.” PLoS One. 2013 Oct 11;8(10):e77472. doi: 10.1371/journal.pone.0077472. eCollection 2013.

4 Yuan ZY et al. Stereotactic body radiation therapy using the CyberKnife(®) system for patients with liver metastases. Onco Targets Ther. 2014 Jun 12;7:915-23. doi: 10.2147/OTT.S58409. eCollection 2014.

5 Yoon K et al. Gated Volumetric-Modulated Arc Therapy vs. Tumor-Tracking CyberKnife Radiotherapy as Stereotactic Body Radiotherapy for Hepatocellular Carcinoma: A Dosimetric Comparison Study Focused on the Impact of Respiratory Motion Managements. PLoS One. 2016 Nov 22;11(11):e0166927. doi: 10.1371/journal.pone.0166927. eCollection 2016.

6 Bibault, J-E, S. Dewas, S, Vautravers-Dewas C, Hollebecque A, Jarraya H, et al. Stereotactic Body Radiation Therapy for Hepatocellular Carcinoma: Prognostic Factors of Local Control, Overall Survival, and Toxicity. PLoS One. 2013; 8(10): e77472. Published online 2013 Oct 11. doi: 10.1371/journal.pone.0077472.

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Important Safety Statement: Most side effects of radiotherapy, including radiotherapy delivered with Accuray systems, are mild and temporary, often involving fatigue, nausea, and skin irritation. Side effects can be severe, however, leading to pain, alterations in normal body functions (for example, urinary or salivary function), deterioration of quality of life, permanent injury and even death. Side effects can occur during or shortly after radiation treatment or in the months and years following radiation. The nature and severity of side effects depend on many factors, including the size and location of the treated tumor, the treatment technique (for example, the radiation dose), the patient’s general medical condition, to name a few. For more details about the side effects of your radiation therapy, and if treatment with an Accuray product is right for you, ask your doctor.