The CyberKnife System offers patients a new option for spine cancer treatment5. Unlike conventional radiation therapy, during which low doses of radiation are delivered over weeks and months, the CyberKnife System can treat a tumor in one to five days by delivering a high dose of radiation with extreme accuracy.
Spine tumors present a treatment challenge because they move as the patient breathes. Conventional radiation therapy cannot account for this movement, so surrounding healthy tissue is damaged by the radiation. The CyberKnife System is able to achieve a high level of accuracy completely non-invasively – without the use of body frames or implanted fiducial markers. It can pinpoint a tumor’s exact location in real time throughout treatment7.
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The CyberKnife System allows the patient to breathe normally while on the treatment table, enabling the doctor to zero in on the moving tumor and focus hundreds of radiation beams from different angles, all of which intersect at the tumor. Using this method, the CyberKnife System is able to deliver a high dose of radiation to the tumor while avoiding damage to the surrounding sensitive spinal cord tissue and other critical structures. As a result, radiation is delivered more accurately and treatments can be performed in a shorter period of time6.
Clinicians using the CyberKnife System have pioneered the treatment of spine tumors with radiosurgery and it was more than 10 years ago that the first CyberKnife patient was treated for spine cancer5
CyberKnife treatments involve a team approach, in which several specialists participate:
- a neurosurgeon
- an orthopedic surgeon
- a radiation oncologist
- a medical physicist
- a radiation therapist
- other medical support staff
Once the team is in place, preparation for the CyberKnife treatment will begin. Generally there are three steps involved:
- Set up and imaging
- Treatment planning
- CyberKnife treatment
During set-up and imaging, the patient may be fitted for a custom body cradle, which is designed to help keep the patient more comfortable and ensures he or she is in the same position for both imaging and treatment.
If the tumor is in the upper cervical region, the patient also may be custom-fitted with a mesh face mask. Both the cradle and face mask are painless and completely non-invasive.
While laying in the body cradle and/or wearing the face mask, the patient will undergo a computed tomography (CT) scan. This scan data will be used by the CyberKnife team to determine the exact size, shape and location of the tumor. A magnetic resonance image (MRI) or some other type of imaging study also may be needed to fully visualize the tumor and nearby anatomy. Once the imaging is done, the body cradle or face mask will be stored for use during treatment.
Treatment planning is then performed by a medical physicist in conjunction with the treatment team. The patient will not need to be present at this time. During treatment planning, all CT, MRI and other scan data will be downloaded into the CyberKnife System’s treatment planning software to develop a customized treatment plan. The medical team will determine the size of the area being targeted by radiation and the dosage, as well as identifying critical structures – such as the spine or vital organs – where radiation should be minimized. The CyberKnife System calculates the optimal radiation delivery plan to treat the tumor. The treatment plan will take full advantage of the CyberKnife System’s maneuverability, allowing for extremely accurate delivery of radiation.
After the plan is developed, the patient will return to the CyberKnife center for treatment. The doctors may choose to deliver the treatment in one session, or stage it over several days. Typically, treatments are completed in one to five days.
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.
If lying on one’s back is painful, the doctor may instruct the patient to take pain medication prior to the CyberKnife treatment in order to minimize any discomfort.
After arriving at the CyberKnife center, the patient will be escorted into the treatment room, placed in the body cradle and/or face mask and then positioned on the treatment couch. The patient will be monitored through closed circuit television and be able to communicate with the treatment team at all times.
When treatment begins, the CyberKnife System will use X-rays to place the patient into the proper position and pinpoint the location of the patient’s tumor. The CyberKnife System’s computer-controlled robot will move the radiation source to multiple locations around the patient as they lie still on the table. Throughout the treatment, more digital images of the spine will be captured by the image guidance system in order to verify the tumor location. If the patient moves slightly, the change is detected by the imaging system, which automatically adjusts the robotic arm before delivering the radiation. By adjusting in this manner, the radiation beam can accurately target the tumor throughout the entire treatment process and minimize damage to healthy tissue.
Nothing will be required of the patient during the treatment, except to relax and lie as still as possible. In fact, patients often sleep through the treatment.
There are generally only minimal side effects from CyberKnife treatments. Occasionally patients report mild, temporary nausea, particularly if the lower abdomen is undergoing treatment. Prior to treatment, the doctor will discuss with the patient all possible side effects they may experience. The doctor also may prescribe medication designed to control any side effects should they occur.
After completing the CyberKnife treatment, patients should schedule and attend all follow-up appointments. Patients must keep in mind that the tumor will not suddenly disappear. In fact it could take several months, or longer, to determine the effectiveness of the CyberKnife treatment. Response to treatment varies from patient to patient. Clinical experience has shown that most patients respond very well to CyberKnife treatments. By routinely evaluating the symptoms and undergoing post-operative MRIs, the doctor can chart the patient’s post-treatment progress.