Every year, thousands of patients are diagnosed with cancer. Their therapies often include a complex interplay of different modalities. Surgeons, medical oncologists and radiation oncologists work closely in the treatment of these patients and use cutting–edge surgical techniques, new novel chemotherapy agents and advanced technologies in radiation oncology.
New imaging technologies coupled with complex radiation delivery systems now allow physicians to better target tumors while at the same time protecting normal organs. Techniques, such as intensity modulated radiation therapy (IMRT), allow improved mapping of the tumor size while the image guided radiation therapy (IGRT) gives “real–time” information, allowing the radiation oncologists to see tumor movement and verify proper target coverage.
The CyberKnife is a new and exciting form of technology that merges all of the above modalities with the use of a robotic delivery system. It can be used for the treatment of tumors throughout the body by using very high doses of radiation in a small number of treatments that are delivered to a precise location. This technique of utilizing high–dose delivery using advanced targeting modalitiesis referred to as stereotactic radiosurgery (SRS). Other delivery systems have used SRS to successfully treat many intracranial tumors, as well as other benign processes, such as arteriovenous malformations (AVMs), and debilitating conditions, such as trigeminal neuralgia.
The CyberKnife uses a miniature linear accelerator (LINAC) attached to a robotic arm to deliver focused radiation to a tumor from multiple positions and angles. By using real time image guidance, the CyberKnife system is able to track the exact position of the tumor in the body and deliver a highly focused dose of radiation that converges on the tumor. Thus, the tumor receives a cumulative dose of radiation that is high enough to control or kill the tumor cells while minimizing radiation exposure to surrounding healthy tissue.
By employing a moving robot, the CyberKnife system now allows physicians to extend the reach of SRS to also treat tumors located throughout the central nervous system, including the brain and spine region, as well as other organs. It is also used to re–treat many tumors that have been previously irradiated using conventional techniques and could not otherwise be treated without compromisingnormal surrounding tissues.
Recent advances in software, such as the Synchrony System, allow the CyberKnife to treat many tumors affected by normal breathing cycle movement, including lung, liver, pancreas and kidney cancers. It allows the precise delivery of dynamic radiosurgery, i.e. the ability to radiate a tumor while it is moving within the body. The Synchrony System utilizes a vest worn by the patient that is embedded with tiny positioning electrodes coupled with tiny radiopaqe markers implanted in or near the tumor.As the patient breathes normally, real–time information is transmitted to the robot, allowing it to “know” the exact position of the tumor so that radiation is delivered only to the target desired.
Further technological and software refinements will allow faster treatment times and better tumor targeting and tracking. Many ongoing protocols are underway, and stereotactic radiosurgery will be used for the definitive treatment of specific tumors, such as prostate and lung cancers.
The success of the CyberKnife treatment depends on a multidisciplinary team approach. This group includes radiation oncologists, surgeons, physicists, dosimetrists, radiation therapists and nurses. Because the procedure does not involve any invasive interventions during the treatment, it can often be performed as an outpatient procedure and does not require any sedation or anesthesia.
