The CyberKnife System has been used to treat pancreatic cancer in patients who are poor surgical candidates, those who refuse surgery and in patients for whom surgery or other treatments have failed. Two clinical studies from Stanford University8-9 have shown the growth of pancreatic tumors in patients with advanced disease has been controlled by CyberKnife radiosurgery. One study estimated the six-month survival at 80 percent and the estimated one-year survival at 15 percent.9 In another preliminary study, CyberKnife treatment was shown to provide pain control in 85 percent of the treated patients.10
Treating tumors in and near the pancreas with radiation is challenging because those tumors move as you breathe, making it difficult to target them accurately with radiation. As a result, the tumor may not receive enough radiation and healthy tissue near the tumor may be damaged. With other kinds of radiation therapy – often referred to as conventional, external-beam, or intensity-modulated radiotherapy – the total radiation dose is divided up into smaller doses delivered over 25 to 40 sessions in order to minimize damage to surrounding healthy tissue. CyberKnife radiosurgery is intended to destroy, or ablate, the tumor tissue with high doses delivered in one to five sessions. To do that safely requires a highly accurate system that detects the movement of the tumor throughout treatment sessions and delivers the radiation with pinpoint precision.
Working in conjunction with the CyberKnife System 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 System, doctors can zero in on a moving target – the pancreatic 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.
Pancreatic cancer treatment with the CyberKnife System involves a team approach, in which several specialists participate. A team may include:
- a surgeon
- a radiation oncologist
- an interventional radiologist
- a medical physicist
- a radiation therapists
- medical support staff
Once the team is in place, the patient will begin preparation for CyberKnife treatment. The CyberKnife treatment generally involves four steps:
- Fiducial placement
- Set-up and imaging
- Treatment planning
- CyberKnife treatment
During the first step of the treatment process, the patient is scheduled for a short outpatient procedure in which three to five fiducials – tiny gold seeds each about the size of a grain of rice – are inserted into the pancreatic tumor using CT guidance. The CyberKnife System uses those markers as reference points to identify the exact location of the pancreatic 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, the patient 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 scan also may be necessary to fully visualize the tumor, pancreas and nearby anatomy. Once the imaging is done, the body cradle will be stored for the remaining CyberKnife treatments.
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 CT and MRI scan 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 minimized. Each patient’s unique treatment plan will take full advantage of the CyberKnife System’s extreme maneuverability, allowing for a safe and accurate pancreas cancer treatment.
After a treatment plan is developed, the patient returns to the CyberKnife center for treatment. Pancreatic cancer treatment is usually delivered in four to five sessions, which 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 pancreas 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 System tracks the patient’s pancreas tumor as it moves, and safely and precisely delivers radiation to it.
The CyberKnife System’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 pancreas tumor as it moves. Nothing will be required of the patient during treatment, except to relax and lie as still as possible.
Once treatment is complete, most patients quickly return to their daily routines 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. Early results indicate that patients tolerate the CyberKnife procedure well, and it does not impair pancreas function. 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 tumor will not suddenly disappear. Response to pancreas 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 using imaging studies and evaluating his or her symptoms.