What is CyberKnife®?
Conventional radiotherapy uses large field sizes and just a few radiation beams to treat ‘regions’ in the body which means the dose given to the tumour is often limited by the radiation tolerance of surrounding normal tissues. The CyberKnife® system is completely different as it uses hundreds of pencil thin beams and thousands of potential treatment angles to target individual tumours.
The machine consists of a highly manoeuvrable miniaturised linear accelerator (a machine that delivers high energy x-rays) attached to a robotic arm. Bavarian Motor Works (BMW) originally created this robotic arm for manufacturing their cars. This robotic arm is complimented by a state-of-the-art targeting system which pinpoints tumours with sub-millimetre accuracy and then fires in hundreds of high dose pencil-thin beams of radiation.
What makes CyberKnife® so special?
It is a very accurate form of radiation treatment that can be used as an alternative to surgery in many cases. The key is delivering the right dose to the right place at the right time whilst minimising damaging effects on normal tissue. I like to think of it as “precision without incision”. Technology advancements enable the use of highly innovative and sophisticated planning and targeting software to treat tumours, even moving up and down to track the target as the patient breathes, minimising any radiation dose to normal tissues.
Theoretically any tumour target can be cured with radiation therapy, historically this has been limited by the tolerance of surrounding normal tissue; CyberKnife® has changed this concept overnight with obliterative doses of radiation delivered rapidly and with absolute precision. In radiotherapists’ terminology it combines extreme hypo fractionation (where radiation is given in larger doses or ‘fractions’ and in less sessions than traditional radiation therapy) with intrafraction Image Guided Radiotherapy (IGRT) and extreme Intensity Modulated Radiotherapy (IMRT) to produce a near-perfect dose distribution of radiation around the target, with minimal dose to surrounding healthy tissue. This enables the very high doses used to be given with absolute safety and confidence.
What can CyberKnife® treat?
Patients who were previously untreatable may now have hope. The CyberKnife® System can treat tumours all over the body and not just the brain as per some older machines. What makes it unique is that it can be used as an alternative to invasive conventional surgery in many cases.
Major operations such as lung and liver resections, removal of pancreas and prostatectomy now have a viable alternative option with this technique.
Tumours in the body
Current indications include the treatment of stage 1 or 2 non-small cell lung cancer, lung metastases, spinal tumours, locally advanced pancreatic tumours, early prostate cancer, and treatment of primary or secondary liver tumours. This technology can also be used to retreat cancers that have recurred following conventional radiotherapy, for example head and neck or rectal cancers. These are situations that were previously untreatable using radiation.
Tumours in the brain and spine
Within the brain CyberKnife® can be used for the same indications as Gamma Knife including brain metastases, pituitary tumours, acoustic neuromas, meningiomas, AV malformations and trigeminal neuralgia. The use of 6-dimensional skull tracking makes this treatment at least as accurate as gamma knife without the inconvenience of a frame bolted to the patient’s skull. With the opening of the cancer centre, The London Clinic will have an essential tool for patients with limited disease as Cyberknife® is not usually appropriate for patients with widespread metastases.
What happens before treatment?
Patients will have a CT planning scan in order for the clinical oncologist, radiologist and physicist to determine the correct treatment volume, organs at risk, and radiation dose distribution. This scan can be fused with other imaging modalities such as MRI, PET scans and 3D angiography. Some tumours require the implantation of metallic markers, the size of a grain of rice (called fiducial markers), which help the software track the tumour more accurately. This can usually be done under local anaesthetic, one week before treatment. The treatment is explained in detail to each patient at a dedicated consultation, where discussions of any possible side effects will also take place. Due to the accuracy of targeting there have been very few serious side effects.