What Is a Cyberknife?
A cyberknife is a robotic device that performs radiosurgery to treat cancerous and noncancerous tumors anywhere in the body. The device delivers precise high-dose radiation to the tumors without interfering with the normal cells. Although the description mentions the word radiosurgery, in reality, there is no surgery involved. Radiosurgery is the same as radiation therapy provided to cancer patients but in a higher dose and precision.
Cyberknife is the first and only robotic device that is approved to treat tumors anywhere in the body. It is a non-surgical option for patients with inoperable complex tumors.
How Does Cyberknife Work?
Cyberknife works on two principles. They are-
1. Three-dimensional Target Localization- A cyberknife uses a 3D coordinate system with image enhancement to fabricate an accurate radiotherapy plan. Conventional systems deliver the dose of radiation based on the information feed that a radiotherapist manually enters into the device; any changes in the dose are also done by the professional.
A cyberknife has a built-in 3D imaging system that provides real-time image guidance; it can be used to locate tumors anywhere in the body; the different tumor-tracking systems it uses are-
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6D skull to locate and track tumors in the brain.
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X site spine for tumors in the spine.
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X site lung with synchrony for tumors in the lungs.
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Fiducial tracking for tumors in the liver, prostate, breast, etc.
Other than the imaging system, a few important components of the device are the linear accelerator and the robotic arm. The accelerator that produces and delivers the radiation and the robotic arm that gives the accelerator the flexibility that it needs to shoot the radiation beams from all possible directions.
2. Radiation Precision- The device has a synchrony tracking feature that can track any moving target in a phased manner, also incorporating breathing cycles. So, if an individual, unfortunately, moves during the procedure, the machine can sense the movement and directs the radiation to the tumor, which is now at a different angle due to the patient's movement.
The cyberknife has sub-millimeter accuracy in tracking the tumor, which is extremely useful in reducing normal tissue damage. During surgery and radiotherapy, the clinician removes and destroys quite a bit of normal tissue surrounding the tumor to make sure that there are no remnant cancer cells that might cause recurrence of the tumor. In this cautionary step, the healthy tissue is unnecessarily damaged; this is avoided in cyber knife radiosurgery.
The device can mark the location of the tumor with a margin of a few sub-millimeters; if this accuracy is not achieved, it gives a warning and stops the treatment. It also takes an X-ray before and after every beam of radiation to assess the further dose and angle.
How Does Cyberknife Destroy Cancer?
Cyberknife damages the cancer cells through a couple of mechanisms-
1. Double Impact- The theory of hypofractionation applies to cyberknife. During the treatment, large doses of radiation with deep and irregular gradients are given at shorter intervals. This doubles the impact, the larger dose penetrates deep into the tumor on an expo facto basis, and the short duration prevents the cancer cells from entering into a resting phase.
The resting phase is present in all living cells, normal cells use this time to recuperate after cell division, but cancer cells skip this step cause they are in a constant state of frenzy to multiplicate.
Radiation therapy destroys the cancer cells by preventing DNA (deoxyribonucleic acid) replication that happens during the dividing phase of the cell; the cancer cells, which are in a constant dividing phase, change themselves to the resting phase as a coping mechanism during radiation. The cyberknife does not give them enough time for this conversion to happen.
2.Radiobiological Damage- This feature of the cyberknife is relatable to regular radiation therapy. The radiation produced by the cyberknife destroys the blood vessels that supply the tumor, thereby depriving them of the nutrients that are needed for its growth.
What Type of Cancers Can Be Treated With Cyberknife?
As of now, cyberknife treatment is preferred for adults; the curative aspect of it is being explored in early benign lesions, arteriovenous malformations, meningiomas, trigeminal neuralgia, etc. However, as an adjuvant and palliative treatment, it is being used in the following cancers-
Brain, Spine, and Skull-Base Tumors- Cyberknife was actually developed for the treatment of brain and spine tumors. Traditional radiotherapy needed patients in a surgically attached framework to provide precise radiation to the brain tumors; this is eliminated in cyberknife, which uses a tailor-made lightweight and open mesh face mask for precision.
As a result, the patient is more comfortable, which improves the overall experience; the treatment requires one to five sessions to deliver the same dose of radiation which would take ten to thirty sessions by a traditional device.
Head and Neck Cancer- Cyberknife is being used to treat tumors that originate or metastasize to the head and neck. It is often used in combination with intensity modulated radiation therapy (IMRT) and chemotherapy. It can be used to treat tumors in the eye, nose, tongue, salivary glands, windpipe, etc., which in the previous days were only treated during that which resulted in severe disfigurement.
Lung Cancer- Delivering radiation to treat lung cancers is challenging because the lungs expand and collapse during breathing; this affects the accuracy. With cyberknife’s synchrony respiratory tracking system, this complication is eliminated; the sensors in the device track the respiratory movements and modulate the radiation beams accordingly.
Metastatic Cancer- Metastasis is the spread of cancer from its origin to other parts of the body. It is difficult to treat metastatic tumors because most of them metastasize to delicate locations like the brain and spinal cord and, at times, are found wrapped around critical structures, which makes surgery impossible. A cyberknife is the perfect treatment option in these scenarios.
Pancreatic Cancer- Treating pancreatic cancer using conventional radiation therapy usually damages the adjacent liver, thus can be avoided using a cyberknife.
Prostate Cancer- Prostate cancer that does not meet the criteria for brachytherapy can be treated with a cyberknife.
Trigeminal Neuralgia- Although technically not a tumor, trigeminal neuralgia is the most painful neurological condition that affects the entire half of the face. Medical therapy does not manage the pain effectively, and often patients seek surgery to remove part of the nerve causing the pain.
Cyberknife can treat this without surgery by delivering radiation beams to the trigeminal nerve with pinpoint accuracy. There is no cutting, blood loss, and hospital stay.
Although, in theory, a cyberknife aims to eliminate only cancer cells, often adjacent tissue does get affected, which can be reversed with sufficient oxygenation. The treatment is often used as a palliative or adjuvant therapy and is yet to receive the mainstream status that it is intended for.
Conclusion:
Cyberknife uses state-of-the-art technology and can treat a wide range of cancers, noncancerous lesions, and other conditions. Although it is completely automated, which decreases the diagnostic and treatment errors, a high degree of understanding and training is needed before the system is put to use in a clinical setting. As of now, it is used as a curative treatment in a small number of malignancies, which hopefully will be expanded in the future.
