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| REVIEW ARTICLE |
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| Year : 2015 | Volume
: 27
| Issue : 1 | Page : 72-75 |
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CyberKnife radiosurgery: Precision without incision
Enja Siva Prasad Reddy, Shruti Sinha, Sunira Chandra, Shruti Chandra
Department of Oral Medicine and Radiology, Saraswati Dental College and Hospital, Lucknow, Uttar Pradesh, India
| Date of Submission | 05-May-2015 |
| Date of Acceptance | 28-Sep-2015 |
| Date of Web Publication | 12-Oct-2015 |
Correspondence Address:
Shruti Sinha
Department of Oral Medicine and Radiology, Saraswati Dental College and Hospital, Faizabad Road, Tiwari Ganj, Lucknow, Uttar Pradesh
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0972-1363.167088
 Abstract | | |
CyberKnife stereotactic radiosurgery system is an innovative, effective, frameless, non-invasive substitute for conventional surgical treatment of cancer. It works on the principle of stereotaxy. It is used for the treatment of both cancerous and non-cancerous tumors, intracranial lesions, tumors of lung, spine, prostate, and kidney, recurrent cases of oral squamous cell carcinoma, arteriovenous malformation, and trigeminal neuralgia. It has an advantage over other systems like Gamma knife radiosurgery and linear accelerator (LINAC)-based systems, as it is frameless, has submillimeter accuracy, does not affect the normal cells adjacent to the lesion, and tracks the lesion in synchronization with the patient's respiratory rate. The future of CyberKnife encompasses possibilities such as incremental improvements in accuracy and better shaping of the field of radiation and would certainly allow extension of radiosurgery as an effective substitute for chemotherapy. This paper aims to review and highlight the immense potential that CyberKnife holds in the field of dentistry in treating disorders of the head and neck region, thereby ensuring enhanced longevity for the patients. Keywords: CyberKnife, head and neck cancer, linear accelerator, radiotherapy, recurrent tumors, stereotactic neurosurgery, stereotactic radiosurgery, stereotaxy
How to cite this article:
Reddy EP, Sinha S, Chandra S, Chandra S. CyberKnife radiosurgery: Precision without incision. J Indian Acad Oral Med Radiol 2015;27:72-5 |
How to cite this URL:
Reddy EP, Sinha S, Chandra S, Chandra S. CyberKnife radiosurgery: Precision without incision. J Indian Acad Oral Med Radiol [serial online] 2015 [cited 2020 Oct 31];27:72-5. Available from: https://www.jiaomr.in/text.asp?2015/27/1/72/167088 |
| Introduction | |  |
CyberKnife is a stereotactic radiosurgery system which, as the name suggests, does not use any knife or scalpel. It is an amalgamation of the basic principles governing "radiotherapy" and "stereotactic neurosurgery." Stereotaxy is a computer-based three-dimensional (3D) co-ordinate system with pre-calculated trajectories. As a nominal approach, it allows ingenious conservation, low risk, and high sensitivity. It is a non-invasive treatment to ablate the tumor or lesion, as the high dose of radiation targets the area specifically from multiple angles without damaging the nearby tissues and adjacent critical structures. It is a revolutionary advancement in the field of radiosurgery which has changed the way lesions are treated and has overcome the limitations of stereotactic radiosurgery. [1],[2],[3]
Horsley and Clarke in 1908, invented the first stereotactic apparatus to locate the cerebellum of a rat. In 1940, Spigel and Wycis invented the stereotactic system for humans, which was later used for treating tremor-related disorders. [1] A Swedish neurosurgeon, Dr. Lars Leksell, gave the concept of radiosurgery in 1950 and along with Traugott Riechert, Robert, and Wells, he invented stereotactic methods of radiosurgery to determine the location of tumor by linear coordinates. [1],[2] Dr. John Adler, a neurosurgeon in Stanford, USA, invented CyberKnife in 1990s with the major advantage of elimination of head frame and treatment of both intracranial and extracranial lesions. [2]
| Technique | | |
It works on the dynamic principle of stereotaxy which is defined as "operating in a 3D space with pre-calculated directions (trajectories)." [1],[2] The four different tumor tracking facilities used are 6D skull, which is used for lesions that are located intracranially, Xsight spine, Xsight lung with synchrony, and fiducial with synchrony. [2] CyberKnife enables the irradiation of tumor or lesion without damaging the adjacent critical structures. [2]
CyberKnife unit has two main components, i.e. the linear accelerator and the robotic arm [Figure 1]. High-energy X-rays are delivered to the area of tumor by the linear accelerator (6 MeV with radiation dose of 4 Gy/min) which is light in weight and attached to the robotic arm. [2],[3] The robotic arm has six degrees of freedom of movement and can achieve 1200 positions. Non-isocentric beams can be directed from any angle. Infrared cameras have been incorporated into it that send online information to the robot after following the breathing movements of the patient, which guides the linear accelerator (LINAC) into proper position. The robotic arm moves in synchrony with the breathing movements, which is known as "breath-triggered real-time movement correction system." [3] The collimators which limit the size of radiation and reduce the patient's exposure are available in 12 sizes ranging from 5 to 60 mm. [4] Fiducial is a metal marker (5 mm) which is implanted percutaneously to locate the area to be irradiated precisely. It acts as reference point for the radiation beams. It is used in case of lesions involving organs which show movement, like the lung, liver, and pancreas. [3] The image fusion software is used which combines other imaging modalities like computed tomography (CT), positron emission tomography (PET), single-photon emission computed tomography (SPECT), and magnetic resonance imaging (MRI) and helps in precisely locating the lesion and improves the outcome of treatment. [1] Silicon detectors are used to record the images in digital format [Figure 2]. The patient remains awake during the treatment and it is a painless procedure. A session of radiosurgery takes 60-90 min depending on the site, volume of lesion, and the risk factor of organs. [3] It works on the principle of dose painting, which is radiation delivery from one edge of the tumor to the other. [2] Treatment can be divided into several stages depending upon the volume to be irradiated. [3]
| Applications | | |
It is the treatment of choice in cases where further surgery is not feasible, like in inaccessible lesions, lesions lying in close proximity with critical structures, and irregularly shaped tumors, as it spares the adjacent normal cells. [3],[5] It is indicated as the first-line treatment for recurrent and residual tumors where prior radiotherapy treatment has been done, like in case of oral cancer. In 2002, Ishimaru et al. treated a 64-year-old woman, who had oral squamous cell carcinoma with extensive invasion of the primary tumor and had already undergone superselective intra-arterial chemoradiotherapy, with CyberKnife and were able to achieve a complete recovery of the case. [6]
It is indicated as the line of treatment for head and neck cancers. In 2014, Bonomo et al. conducted a study where they treated various sites of head and neck cancer (five patients for neck lymph nodes, five for paranasal sinuses, two for oropharynx, and one patient each for nasopharynx, larynx, oral cavity, nasal fossa, and parotid gland) with CyberKnife. Of these, 16 patients (94%) were evaluated. At a median follow-up of 7.5 months, four patients showed complete response (25%), five achieved partial response (31%), and seven had stable disease (44%). No side effect was noted at late stages. [7] In 2014, Yamazaki et al. conducted a study where they took 11 nasopharynx, 7 oropharynx, 1 hypopharynx, 3 nasal cavity and paranasal sinus, and 3 oral cancers that had been already treated with conventional radiotherapy and treated them with CyberKnife. The overall treatment response rate was 96% (24/25) with 18 patients showing complete response, 6 showing partial response, and 1 had progressive disease. [8] In another study conducted by Tsai et al. in 2013 where CyberKnife was the chosen treatment modality in patients suffering from vestibular schwanomma, 117 patients had excellent tumor control rates (99.1%) with a mean imaging follow-up of 61.1 months. [9]
CyberKnife has proved to be an excellent procedure in the treatment of trigeminal neuralgia. In a review of 10 studies that was reported by Gibbs et al. in 2009, in which trigeminal neuralgia was treated with CyberKnife, 77-96% patients reported initial pain relief and 4.8-34% reported recurrence of pain. CyberKnife shows the same success rate as that of microvascular decompression and percutaneous procedures. [10] Other neurological disorders where CyberKnife can be used are acoustic neuromas, meningiomas, and brain metastases. [1],[3],[10],[11] In 2015, Basu et al. conducted a study in which four patients suffering from adrenal tumor were treated with CyberKnife with a median dose per fraction of 10 Gy. After 8-12 weeks, check-up was done which revealed that two had complete recovery and two had partial recovery. [12]
Other stereotactic systems like Gamma knife and LINAC were used to treat intracranial lesions, but with recent advancements in technology, CyberKnife has emerged as a whole-body stereotactic radiosurgery system. [2] It is also an indication for extracranial tumors, and small tumors in the lung, liver, spine, and pancreas. [1],[3],[5],[13] In 2013, Yuan et al. conducted a research where hepatocellular carcinoma was treated with CyberKnife and showed less adverse effects, with 1-, 2-, and 3-year local control rates of 92.9%, 90.0%, and 67.7%, respectively. The survival rates of the patients treated by CyberKnife were 72.7%, 66.7%, and 57.1%, while of those treated surgically were 88.5%, 73.1%, and 69.2%, respectively. [14]
| CyberKnife Over Other Techniques | | |
The major advantage of CyberKnife radiosurgery is its precision, as the radiations can be projected from many directions, cross-firing the lesion in an accurate manner with submillimeter accuracy. If this exactness is not achieved, the machine gives a warning signal and the treatment does not proceed. Other LINAC-based systems have millimeter accuracy as opposed to CyberKnife, as digital images are taken before the beams are fired to enhance the accuracy. [2] Conventional radiotherapy has 5-20 mm target accuracy, while CyberKnife and Gamma knife have <1 mm target accuracy. [15] High doses of radiation can be given to the affected area with minimal harmful effects on the nearby normal tissues and other critical structures adjacent to the lesion. This feature makes it an ideal treatment option over conventional radiotherapy, as it requires negligible margins for the setup and the dose ascent is deeper. [3] CyberKnife has the ability to fractionate doses, while this is not possible in Gamma knife surgery. Ability to target tumor with breathing movements and real-time imaging are the exclusive features of CyberKnife. [15] For tumors of small size, it is considered to be the best treatment alternative, apart from surgical procedure. [5] It is a pain-free, non-invasive treatment procedure as it does not require any invasive stereotactic frame, while frame is required in Gamma knife therapy and immobilization in conventional therapy. [2],[3],[15] Neither general anesthesia nor stay in hospital or rehabilitation is needed, and patient can resume his/her daily activities. [3]
| Limitations | | |
It is a technique-sensitive procedure. So, it involves a team of radiation oncologists, medical physicists, and technologists for the successful outcome of treatment. [2] Longer treatment time, i.e. more than 40 min, may pose a problem in pediatric patients, where adequate sedation and immobilization is needed, and in elderly patients suffering from respiratory disorders and bladder insufficiency. [5] Re-irradiation has been associated with harmful complications such as necrosis, focal edema, and hemorrhage, while no such complications have been encountered in patients who underwent only radiosurgical procedure. As CyberKnife treatment involves delivery of high dose of radiations, negligence can result in death of patient. [15],[16],[17]
| CyberKnife in India | | |
Depending on the location, size, type of tumor, and the number of sessions required, the cost of CyberKnife technology varies in India (approximately it amounts to Rs. 500,000). The number of sessions may vary from one to five. Conventional surgery involves more expenditure as the duration of stay in hospital is more and the associated expenses increase, while CyberKnife does not involve such extra costs. [15]
Treatment is available for benign tumors like pituitary adenoma, acoustic neuroma, malignant tumors, head and neck cancers like lip and oral cavity cancer, oropharyngeal cancer, nasopharyngeal cancer, etc., arteriovenous malformations, cavernous malformations, functional disorders like trigeminal neuralgia and cluster headache, lung cancer, liver cancer, renal cell cancer, and prostate cancer. At many centers in India like BLK CyberKnife Centre at BL Kapur Memorial Hospital in New Delhi, Apollo Hospital in Chennai, and Medanta Hospital in Gurgaon, treatment is available. [18],[19],[20]
| Conclusion | | |
CyberKnife has proved to be an accurate, safe, superior, and sophisticated approach for the treatment of intracranial and extracranial lesions. In dentistry, it is being successfully used to treat oral cancer and trigeminal neuralgia. The technological advances in stereotactic neurosurgery will show the way for further extension in treatment. New research activities are aimed at utilizing the full potential of robotics in radiosurgery and also on the prospective enduring side effects. By use of an optimized path traversal process, the overall treatment time is reduced by 5-10 min. Monte Carlo algorithms have been used to calculate the accurate dose required. The IRIS collimator decreases the treatment time, requires less monitor units, and provides more homogeneity of treatment. Fiducial-less treatment is possible now with the use of real-time image guidance. Treatment of depression, obsessive compulsive disorder, Parkinsonism More Details, non-small cell lung tumor, etc. by CyberKnife is still under research. Another aim is to treat low-volume tumors. Xsight lung tracking, an algorithm for fiducial-less lung tracking, has been developed for peripheral, radiodense lung tumors with diameters >15 mm. With all these advancements, it will certainly give way to further improvements in the treatment accomplishment for patients, while lowering certain limitations.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
| References | | |
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