Treating liver cancer with radiation therapy is a challenge because liver tumors move with respiration. In addition the tissue surrounding the liver tumors is very sensitive and can be damaged easily. The CyberKnife is able to deliver very high doses of radiation to both primary and metastatic liver tumors with extreme accuracy. Working in conjunction with the CyberKnife is the Synchrony® Respiratory Tracking System, which enables the radiation beam to track tumor movement in real time and allows patients to breathe normally during their treatment sessions.
With the CyberKnife, doctors can zero in on a moving target – the liver tumor – 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.
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 tumor using CT guidance, ultrasound or via a camera that is passed through the mouth into the stomach and small intestine. The CyberKnife uses those fiducial markers as reference points to identify the exact location of the tumor 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 stabilized.
During set-up 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 tumor position. The data generated with the vest allows the CyberKnife robot to precisely follow the tumor’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 tumor. An MRI or PET-CT scan also may be necessary to fully visualize the tumor, 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 present at this time. During treatment planning, the imaging data is downloaded into the CyberKnife’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 minimized. Each patient’s unique treatment plan will take full advantage of the CyberKnife’s extreme maneuverability, allowing for a safe and accurate liver cancer treatment.
After a treatment plan is developed, the patient returns to the CyberKnife center for treatment. 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. Patients dress comfortably in their own clothes and, depending on the treatment center, they may be allowed to bring music to listen to during the treatment. Patients also may want to bring something to read while they wait, and have a friend or family member with them to provide support before and after treatment.
When it is time for treatment, the patient will be asked to put on their Synchrony vest and lie on their custom body cradle. The radiation therapist will ensure the vest is properly adjusted and that the patient is positioned correctly on the treatment couch.
As treatment begins, the location of the liver tumor 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 tracks the patient’s liver tumor as it moves, and safely and precisely delivers radiation to it.
The CyberKnife’s computer-controlled robot will move around the patient’s body to various locations from which it will deliver radiation. At each position, the robot will stop. Then, special software will determine precisely where the radiation should be delivered by correlating the location of the tumor using digital images of the fiducials and information from the Synchrony vest. The CyberKnife’s robotic arm will adjust the radiation source automatically, to follow the liver tumor as it moves. Nothing will be required of the patient during treatment, except to relax and lie as still as possible.
For more information about CyberKnife, call 253-403-6399.