What Is CyberKnife Treatment and How Does It Function?
CyberKnife provides a non-surgical option to target tumours with precise radiation beams, particularly for challenging sites like the lungs, prostate, or spine. UK NHS centres deliver it as an outpatient treatment across one to five sessions.
In this article, we explain its workings, process, and suitability for patients. Shorter courses cut overall treatment time by 80% compared to daily radiotherapy over weeks.
What Is CyberKnife?
CyberKnife is a radiosurgery system that mounts a radiation source on a robotic arm to strike tumours from many angles without cutting into the skin. NHS trusts use it for over 30 cancer sites, from early lung cancers to spine metastases. Unlike the Gamma Knife, which is limited to the brain, CyberKnife adapts to body movement across the torso or the head. Sessions can be finished in 30 to 90 minutes, and patients can head home the same day.
This technology entered UK practice in the 2010s, with NICE approval for prostate cancer by 2019. No general anaesthetic comes into play, just light sedation if needed. Local control rates reach 90% at three years for stage one lung cancers unfit for surgery. Its robotic design lets it treat spots that surgery skips.
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How CyberKnife Functions
A planning CT or MRI scan builds a detailed 3D map of the tumour, often fused with PET images to pinpoint exact edges and avoid critical structures such as blood vessels or nerves. The robotic arm moves fluidly around the patient, delivering up to 1,200 narrow radiation beams from different angles that converge precisely on the target. Doses concentrate 95% within the tumour, with a sharp fall-off at the borders to limit exposure to surrounding healthy tissue. This conformal shaping fits oddly shaped or near-sensitive areas better than static linear accelerators.
Cameras capture X-ray images every few seconds to track the tumour's position, while software makes split-second adjustments to the robot's path. In lung or liver treatments, it synchronises with breathing patterns that shift targets by up to two centimetres, using predictive models to anticipate motion. If the tumour drifts too far, the system pauses the beam automatically through gating. Millimetre accuracy supports 2-3 times higher doses per session than conventional radiotherapy, enhancing tumour kill rates while keeping side effects low.
The Treatment Process
After the scans are completed, doctors usually spend three to five days creating a personalised treatment plan. Computer algorithms are used to map the precise paths of the radiation beams, ensuring they target the tumour as accurately as possible. In certain cases, such as prostate or spinal tumours, tiny gold markers may be placed to improve tracking during treatment.
During each session, patients lie on a comfortable bed and are gently supported with light straps to help them stay in the correct position. Treatment is typically delivered over one to five sessions, spread across one to two weeks. A follow-up scan at around three months is then used to assess how the tumour has responded.
Side effects are generally mild. About 10–20% of patients experience some tiredness or slight skin redness, which usually settles within a few weeks. Referrals to NHS CyberKnife centres take an average of six to eight weeks. Because the treatment is done on an outpatient basis, there is no need for an overnight hospital stay, unlike surgery. The short treatment sessions also make it easier for many people to continue working during their care.
Conditions Treated
CyberKnife is commonly used to treat early non-small cell lung cancer in patients who are too frail for surgery. Through Bristol’s programme, tumour control rates of 85–95% at two years have been reported. In low-risk prostate cancer, around 95% of patients remain free from recurrence at five years. Treatment of spinal metastases relieves pain in about 80% of cases within a month, while liver tumours and recurrent head and neck cancers are also frequent indications.
The treatment is particularly effective for oligometastatic disease, where cancer has spread to a limited number of sites (usually up to three), especially when systemic drug therapies are no longer effective. Ongoing trials are exploring its use alongside immunotherapy to improve outcomes. More widespread disease generally requires chemotherapy first, and tumours smaller than five centimetres tend to achieve the best control.
Advantages Over Other Treatments
Unlike surgery, CyberKnife avoids the risks of infection and prolonged hospital stays, with studies of lung cancer showing complication rates reduced by about half. Traditional radiotherapy can take up to six weeks, whereas CyberKnife treatment is typically completed within days, reducing disruption for patients and easing demand on radiotherapy machines.
While SABR offers similar precision, CyberKnife has an advantage in tracking tumour movement in real time. Fewer treatment visits lead to higher completion rates, particularly among working patients. UK audits also show quality-of-life scores around 25% higher than with combined chemotherapy and radiotherapy. Retreatment rates remain low, at under 10%, and the system’s robotic flexibility allows re-irradiation in patients who have previously received radiation. Most people are able to return to their normal routines within days rather than months.
Potential Risks and Side Effects
Side effects are usually mild and manageable. Fatigue affects around 30% of patients, while nausea occurs in about 10% of those treated in the upper body. These symptoms are typically controlled with rest or anti-sickness medication. Late-onset fibrosis is uncommon, affecting fewer than 5% of patients, and is monitored through follow-up scans.
Some lung cancer patients experience temporary swallowing difficulties, reported in about 10% of cases, which usually resolve. Small shifts in implanted gold markers occur in around 2% of patients and can be corrected by repositioning. People with connective tissue conditions may have a slightly higher risk of fibrosis, so their cases are reviewed carefully. NHS teams monitor side effects weekly during trials, and regular imaging allows very early detection of recurrence. Overall, recovery tends to be quicker than after surgery or chemotherapy.
Who Qualifies?
CyberKnife is most suitable for patients with inoperable stage I–II lung cancer or limited metastatic disease, provided their general health is good. Treatment decisions are made by multidisciplinary teams at specialist centres such as Bristol or Taunton after reviewing scan results. Private clinics may offer faster access for eligible patients.
The technology works best when tumour movement is limited to less than 2 centimetres. Patients who fall just outside standard criteria may be offered entry into UK clinical trials. Age alone does not exclude someone from treatment if they are otherwise fit. GP referrals typically trigger a multidisciplinary team review within two weeks.
Conclusion
CyberKnife uses advanced robotic technology to deliver highly precise radiation, targeting hard-to-reach tumors while minimizing damage to healthy tissue. Its short, carefully planned sessions reduce the need for weeks of daily hospital visits, offering a more convenient option for many patients.
Across the UK, NHS centres are expanding access to CyberKnife, supported by growing clinical evidence and its integration with emerging treatments like immunotherapy. Patients who may be suitable are encouraged to speak with their oncologist, as detailed imaging, including tumor movement, helps tailor treatment to each individual’s needs.