The CyberKnife System offers patients a new option for spine cancer treatment. 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 can be damaged by the radiation. The CyberKnife System is able to achieve a high level of accuracy noninvasively – without the use of body frames (to limit patient movement) or implanted fiducial markers (used as reference points in tumor tracking). It can pinpoint a tumor’s exact location in real time throughout treatment.
The CyberKnife System allows the patient to breathe normally while on the treatment table. It also enables the physician 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. Radiation is delivered more accurately, and treatments can be performed in a shorter period of time.
Clinicians using CyberKnife have pioneered the treatment of spine tumors with radiosurgery, and it has been more than 10 years since the first CyberKnife patient was treated for spine cancer.
Before a typical CyberKnife treatment
CyberKnife treatments involve a team approach in which several specialists participate:
- Orthopedic surgeon
- Radiation oncologist
- Medical physicist
- Radiation therapist
- Medical support staff
Once the team is in place, preparations begin for CyberKnife treatment.
The patient may be fitted for a special custom body cradle. The cradle is made of a soft material that molds to the patient’s body, ensuring that he or she is comfortable and in the same position for imaging and treatment sessions.
If the tumor is in the upper cervical region, the patient also may be custom-fitted with a soft mesh face mask. Use of the cradle and the face mask is painless and completely noninvasive.
While lying in the body cradle and/or wearing the face mask, the patient undergoes a CT scan. The scan data generated is used by the CyberKnife team to determine the exact size, shape and location of the tumor. An MRI or 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 and/or face mask will be stored for use during CyberKnife treatment.
A treatment plan is designed by a medical physicist in conjunction with the treatment team. The patient need not be present. During treatment planning, all CT, MRI and other scan data is downloaded into the CyberKnife System’s treatment planning software to develop a customized treatment plan. The medical team determines the size of the area being targeted by radiation and the dosage, and identifies 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 takes full advantage of the CyberKnife System’s maneuverability, allowing for extremely accurate delivery of radiation.
After the plan is developed, the patient returns to the CyberKnife center for treatment. The physicians may choose to deliver the treatment in one session or stage it over several days. Typically, treatments are completed in one to five days.
The treatment session
For most patients, the CyberKnife treatment is a completely pain-free experience. They may dress comfortably in street clothes, and are free 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 accompany them to provide support before and after treatment.
If it’s painful for the patient to lie on his or her back, the physician may instruct the patient to take pain medication prior to the CyberKnife treatment in order to minimize any discomfort.
At treatment time, the patient lies on his or her custom body cradle and/or puts on the custom face mask. The radiation therapist ensures that the patient is appropriately positioned on the treatment couch. Via closed-circuit TV, the medical team monitors every step as the CyberKnife tracks and precisely delivers radiation to the tumor. The patient is able to communicate with the team at all times.
The CyberKnife System’s computer-controlled robot moves the radiation source to multiple locations around the patient as he or she lies still on the table. Throughout the treatment, more digital images of the spine are captured by the image guidance system in order to verify 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. In this manner, the radiation beam can accurately target the tumor throughout the entire treatment process and minimize damage to healthy tissue.
Nothing is required of the patient during the treatment, except to relax and lie as still as possible.
If treatment is being delivered in stages, the patient will need to return for additional treatments over the next several days, as determined by his or her physicians.
Side effects vary from patient to patient. Some patients experience minimal side effects from CyberKnife treatments. Occasionally, patients report mild, temporary nausea, particularly if the lower abdomen is undergoing treatment. Physicians will discuss all possible side effects with their patients prior to treatment. They may also prescribe medication designed to control any side effects, should they occur.
After completing a CyberKnife radiosurgery treatment, it is important for patients to schedule and attend follow-up appointments. Each patient must keep in mind that his or her 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 one person to another. Clinical experience has shown that most patients respond very well to CyberKnife treatments. By routinely evaluating the symptoms and examining results of post-operative imaging studies, the physician will monitor the patient’s post-treatment progress.
*Source material drawn from www.cyberknife.com. Please refer to that website for a complete listing of references used in the original information sections.
CyberKnife is a registered trademark of Accuray Incorporated.