Accuracy, covering whole body
CyberKnife, stereotactic radiation treatment device is used for treating both malign and benign tumours all around body. Best candidates for treatment are relatively small (under 7 cm) and solid tumours. Clinical accuracy with CyberKnife is always under one millimeter, even 0,3 mm for some areas. Intracranial tumours and tumours near spinal cord are very suitable for CyberKnife treatments. CyberKnife treatment can also be an option for surgery for some cases, where the tumour is inaccessible. With increased accuracy and dose gradient, radiation dose per day can be increased (hypofractionation), leading to fewer visits to radiation therapy department, and shortening the overall treatment time. The adverse effects are not normally increased with hypofractionation. CyberKnife treatment consists usually of 1-6 treatment fractions whereas conventional radiation therapy is usually delivered with 10-30 daily fractions.
The treatment accuracy is being confirmed with continuous imaging during the treatment session. CyberKnife will take into account the possible movement of a patient and a target, which allows the treatments to be delivered without invasive stereotactic frames, fixation devices and tight thermoplastic masks. Most of the CyberKnife treatments are planned with curative intent, aiming to complete curing from cancer. Some of the treatments are delivered in order to relieve difficult symptoms caused by various diseases.
Examples from treatment indications:
Central nervous system
- Benign neoplasms of brains (more under neurosurgery)
- Brain metastasis
- Treatment of the tumour site after surgery
- Reirradiation of brain tumours
Spinal cord and spine
- Tumours inside spinal cord or compressing it
- Treatment and re-treatment of metastasis in vertebral bodies, while sparing spinal cord.
- Treatment of localized lung cancer
- Treatment of separate metastasis in lungs
- Curative treatment of prostate cancer
- Re-treatment of prostate cancer after local failure from brachytherapy
- Tumours / metastasis with difficult locations
- Tumours / metastasis within liver
- Tumours of the pancreas
- Tumours of kidneys
CyberKnife is well suited for treating tumours inside the spinal cord or compressing it. The treatment system uses the anatomy of the vertebra to target the tumour. Because of steep dose gradients, it is possible to spare healthy spinal cord from high radiation doses. For example, the bony structures of vertebra can be treated without irradiating the spinal cord over its tolerance dose.
The CyberKnife system can be used to treat small lung tumours to high doses. The system will take into account the tumour movement during breathing cycle without any fixation devices or diaphragm pressers. The patient can breathe normally during the treatment and the robot will “breathe along” with the patient following the tumor. Because of the treatment accuracy and high dose gradients, large radiation doses can be delivered safely at a time.
The treatments of small lung tumours are performed typically with three treatment fractions (3 x 18-20 Gy). According to recent studies this treatment can even replace the surgery. As a consequence for the inoperable patients, we can offer a treatment which is intent to cure the disease or prolong the disease free time.
If the tumor is located near large vessels in mediastinum or very close to ribs, the fraction dose is reduced. Then the total number of treatment fractions is usually between 5 and 8.
In order to track the tumor, CyberKnife will need a visible target in X-ray images. This can be tumor itself or fiducial markers. If the tumor is not visible in X-ray images, it can be marked with fiducial markers. Markers will be inserted near the tumor with long needles or via angiography.
Following the same principles also single or in some cases multiple metastases in lungs can be treated with the CyberKnife system.
Prostate cancer treatments
Localized prostate cancer is an optimal target for stereotactic radiotherapy. According to radiobiological studies large fraction doses are beneficial for the treatments of prostate cancer. With the high accuracy and steep dose gradients of the system the treatment related uncertainty margins can be minimized and thus the adverse effects will be minimal.
For all the prostate cancer patients treated with CyberKnife, special gold fiducial markers are implanted in the prostate. For the dose planning a computed tomography (CT) and magnetic resonance images (MRI) are needed to visualize the treated area accurately..
The treatment is given in 5 fractions, usually 5 x 7.25 Gy, 2 to 3 times in a week. One treatment fraction will last about an hour. For the patients the shorter fractionation is much more convenient, comparing it to conventional 38 treatment fraction treatments.
Other treatment areas
The radiation treatment of the tumours in liver, pancreas and kidneys is difficult because of the surrounding sensitive organs. The treated targets located in these organs can also be very mobile and can move from day to day and also with breathing. However, CyberKnife can be used to treat these difficult tumours because of its high accuracy, sharp dose gradients and the ability to follow the tumor. Single primary tumors or metastases can be treated within these areas.