How Does the CyberKnife System Treat Liver Cancer?
Treating liver cancer with radiation therapy is a challenge because liver tumours move with respiration. In addition the tissue surrounding the liver tumours is very sensitive and can be damaged easily. The CyberKnife Radiosurgery System is able to deliver very high doses of radiation to both primary (HCC - where it can be used before or after liver transplant as the case may be or in conjunction with TACE (trans arterial chemotherapy or TARE - trans arterial radio embolixation) in inoperable primary cases) and metastatic liver tumours with extreme accuracy. Working in conjunction with the CyberKnife System is the Synchrony Respiratory Tracking System, which enables the radiation beam to track tumour movement in real time and allows patients to breathe normally during their treatment sessions. With the CyberKnife System, doctors can zero-in on a moving target the liver tumour and irradiate it without harming the healthy surrounding tissue. As a result, the CyberKnife treatment is more comfortable for patients, radiation is delivered more accurately and treatments can be completed in one to five sessions.
Liver cancer treatment with the CyberKnife System involves a team approach, in which several specialists participate. A team may include:
Once the team is in place, the patient will begin preparation for CyberKnife treatment. The CyberKnife treatment generally involves four steps:
During the first step, the patient is scheduled for a short outpatient procedure in which three to six fiducials, tiny gold seeds each about the size of a grain of rice, are inserted into and around the liver tumour using CT or ultrasound guidance, . The CyberKnife System uses these fiducial markers as reference points to identify the exact location of the tumour during treatment. Once fiducials are implanted, the patient must wait approximately one week before CyberKnife treatment planning can begin to ensure that fiducial movement has stabilised.
During simulation and imaging, the patient will be fitted for a custom body cradle, which is designed to help keep him or her more comfortable and ensures consistent positioning for both imaging and treatment. The patient also will be fitted with a special Synchrony vest, which is worn during CyberKnife treatment and enables the robot to correlate chest motion and breathing patterns with the tumour position. The data generated with the vest allows the CyberKnife robot to precisely follow the tumour’s motion as it delivers each beam of radiation, ensuring safe and accurate radiation delivery.
While wearing the vest and positioned in the cradle, the patient then will undergo a series of CT imaging studies, which will enable the CyberKnife team to determine the exact size, shape and location of the tumour. An MRI or PET-CT scan also may be necessary to fully visualise the tumour, liver and nearby anatomy. Once the imaging is done, the Synchrony vest and body cradle will be stored for use during CyberKnife treatment.
Next a treatment plan will be specifically designed by a medical physicist in conjunction with the patient’s doctors. The patient does not need to be physically present at this time. During treatment planning, the imaging data is downloaded into the CyberKnife System’s software. The medical team determines the size of the area being targeted by radiation and the radiation dosage, as well as identifying critical structures where radiation should be minimised. Each patient’s unique treatment plan will take full advantage of the CyberKnife System’s extreme manoeuvrability, allowing for a safe and accurate liver cancer treatment.
After a treatment plan is developed, doctors may choose to deliver the liver cancer treatment in one session or stage it over several days. Liver cancer treatments are typically completed within one week. For most patients, the CyberKnife treatment is a completely pain-free experience. When it is time for treatment, the patient will be asked to put on their Synchrony vest and lie on their custom body cradle.
As treatment begins, the location of the liver tumour will be tracked and detected continually as the patient breathes normally. The medical team will be watching every step of the way as the CyberKnife System tracks the patient’s liver tumour as it moves safely and precisely delivering radiation to it.
Once treatment is complete, most patients quickly return to their daily routine with little interruption to their normal activities. If treatment is being delivered in stages, the patient will need to return for additional treatments over the next several days as determined by their doctors. After CyberKnife treatments, most patients experience minimal side effects, which typically go away within the first week or two after treatment. Doctors will discuss all possible side effects prior to treatment. In addition, doctors may prescribe medication to control any side effects, should they occur.
After completing CyberKnife radiosurgery treatment, it is important for the patient to schedule and attend any follow-up appointments. The patient should be aware that his or her tumour will not suddenly disappear. Response to liver cancer treatment varies from patient to patient. It could take several months or longer to determine the effectiveness of the CyberKnife treatment. Doctors will monitor the outcome in the months and years following a patient’s treatment through physical exams, blood tests and imaging techniques, such as CT or PET-CT scans.