Conditions Treated by CyberKnife®
Arteriovenous Malformations (AVMs)
CyberKnife precisely aims radiation beams at the AVM from multiple angles. Over time, the radiation causes the AVM blood vessels to narrow and eventually close off, eliminating the risk of hemorrhage or stroke. The primary advantage over surgical removal is that radiosurgery is not invasive, does not require anesthesia or a hospital stay and doesn’t carry the risks of open surgery. Moreover, some AVMs are located in areas of the brain that cannot be treated with conventional surgery. In those cases, radiosurgery may be the only feasible treatment option.
CyberKnife differs from other radiosurgery systems in that it doesn’t require a rigid metal frame screwed to the patient’s skull for targeting tumors and immobilizing patients. The CyberKnife achieves highly accurate targeting with computer imaging that continuously updates the tumor location and, therefore, eliminates the need for a metal frame.
A benign, slow-growing tumor type, acoustic neuromas affect the seventh and eighth cranial nerves in a part of the brain known as the cerebellar-pontine angle, or CPA. The eighth cranial nerve has two parts – the cochlear nerve that transmits sound between the inner ear and the brainstem, and the vestibular nerve that helps provide balance. Acoustic neuromas most commonly arise from schwann cells, which produce insulation for the vestibular nerve. Therefore, these tumors are often called vestibular schwannomas.
What are the Symptoms?
Early symptoms include hearing loss or deafness, pressure in the inner ear, impaired sense of balance and ability to walk, as well as vertigo with associated nausea and vomiting. About 80 percent of patients reported tinnitus, usually high-pitched ringing, roaring or hissing sounds. Large tumors that press against the brainstem may affect other cranial nerves that result in less common symptoms like the loss of sensation in the face and mouth or altered swallowing and gag reflex. Larger tumors also may lead to increased intracranial pressure and associated symptoms like headache, vomiting and altered consciousness.
Radiosurgery for kidney tumors is noninvasive, and typically carries less risk of complications than conventional surgery. For patients who refuse surgery or have medically inoperable kidney tumors, radiosurgery can be an effective treatment option. CyberKnife, which delivers high-dose radiation over one to five treatments, can be particularly effective for treatment of small kidney tumors. CyberKnife has the ability to compensate for normal patient movements, precisely targeting the tumor during the entire procedure and minimizing damage to surrounding healthy tissue. This is important when treating kidney tumors, which can shift during treatment due to regular patient movements such as breathing.
CyberKnife’s ability to treat tumors with precisely focused radiation offers an important advantage for liver cancer patients. Accurate to within less than a millimeter, radiosurgery has minimal effect on surrounding health tissue. This level of accuracy enables doctors to target liver tumors with high-dose radiation, which significantly reduces the number of treatments needed – usually between three and five over several days compared to 30-40 over several weeks required for conventional radiotherapy systems. Radiosurgery has other benefits as well, namely its ability to track tumors in real time. That means patients breathe normally during each treatment session, since the radiation beam adjusts automatically to the tumor location.
CyberKnife can treat patients who cannot endure surgery or who have a high risk for postoperative complications. CyberKnife can also be used for some tumors that are marginally resectable or unresectable due to their location.
CyberKnife is capable of high-dose radiation for tumors or lesions in especially sensitive areas of the brain and is the only radiosurgery system that doesn’t need an invasive head frame. Radiosurgery with CyberKnife safely delivers high-dose radiation while minimizing exposure to healthy tissue. Ocular and orbital tumors can be difficult to treat due to their close proximity to important structures in the brain, and CyberKnife provides an effective treatment option for these tumors due to the precise nature of the radiation beams it delivers. Ocular and orbital tumors can greatly affect a patient’s quality of life, and radiosurgery with CyberKnife offers a treatment option that can preserve a patient’s vision.
CyberKnife treats pancreatic cancer with high-dose radiation. Clinical studies are ongoing to test the CyberKnife’s effectiveness in treating localized, non-metastatic pancreatic cancer. However, preliminary results involving patients with relatively advanced cases of pancreatic cancer suggest that CyberKnife radiosurgery treatment is well tolerated and provides some clinical benefit.
Prior to treatment, doctors implant between three to five small metal markers known as fiducials in or near the tumor that enable the CyberKnife to pinpoint the tumor location throughout treatment. Implanting the markers is an outpatient procedure that takes about an hour. About a week later, patients are fitted with a custom body mold made of soft material that they lie on during treatments. The fitting process is painless. Patients then undergo a CT scan that assists in developing a customized treatment plan.