CyberKnife Therapy for Liver Cancer
» What is CyberKnife and how can it be used to treat liver cancer?
» When was CyberKnife approved to treat liver tumors?
» What are CyberKnife's advantages for liver cancer treatment?
» How effective is CyberKnife in the treatment of liver cancer?
» What is the process involved in receiving CyberKnife therapy for liver cancer?
» What side effects may be associated with CyberKnife liver cancer treatment?
Q. What is CyberKnife and how can it be used to treat liver cancer?
CyberKnife is a robotically controlled radiation delivery machine. It was originally developed as a device to deliver Stereotactic Radiosurgery (SRS) for tumors of the brain. Now, Stereotactic Body Radiotherapy (SBRT), is approved to treat tumors anywhere in the body, including the liver.
SBRT is a radiation treatment technique in which high doses of radiation are delivered using a very precise beams targeted on the tumor. By using hundreds of focused beams of radiation, a high amount of ablative radiation therapy is delivered to precisely identified areas. The aim is to use such a high dose that the tumor is destroyed, while sparing healthy tissue around it. The radiation coming from the CyberKnife machine is the same type used in standard radiation machines.
Q. When was CyberKnife approved to treat liver tumors?
CyberKnife was cleared by the U.S. Food & Drug Administration in 2001 to treat tumors anywhere in the body, including the liver.
Q. What are CyberKnife’s advantages for liver cancer treatment?
Liver cancers originate in the liver when the liver is affected by hepatitis or cirrhosis. These conditions make the liver vulnerable to damage with conventional radiation. Many liver tumors cannot be removed surgically because they are located near critical blood vessels. CyberKnife therapy is a safe, noninvasive alternative for treating these tumors. CyberKnife is also appropriate for patients who cannot undergo liver cancer surgery for primary or metastatic liver cancers due to their weak medical condition, or who don’t want to undergo surgery. It is non-invasive, with no cutting involved.
A major challenge to treating liver tumors with traditional radiation, or even other SBRT techniques, is that the tumor moves as the patient breathes, constantly moving in relation to nearby critical structures. When this happens, the tumor may not get enough radiation and healthy tissue can be damaged.
As a result, precision targeting of the tumor is critical. CyberKnife ensures this through a highly accurate system that detects and tracks tumor movement continuously during the treatment sessions. It delivers the radiation with pinpoint accuracy. The Synchrony Respiratory Tracking System enables the radiation beam to detect tumor movement in real time and allows patients to breathe normally during treatments. CyberKnife is focused on the tumor, destroying it and sparing the surrounding tissues, typically in three to five sessions.
Q. How effective is CyberKnife in the treatment of liver cancer?
Two studies from Canada have shown that liver tumors are controlled 65 to 75 percent of the time with Stereotactic Body Radiotherapy. Another study from Baylor suggested that SBRT is a useful technique to stabilize tumors in patients waiting for transplantation.
Experience at Beth Israel Deaconess Medical Center has shown that CyberKnife is a feasible and safe technique to treat large and multiple liver cancers. Average survival is 20 months.
SBRT can be combined with other liver-directed therapies like radiofrequency ablation (RFA), Trans Arterial Chemo Embolization (TACE) or systemic therapy.
Q. What is the process involved in receiving CyberKnife therapy for liver cancer?
A team approach is used, involving a surgeon, radiation oncologist, interventional radiologist, a radiation therapist and other support staff. First, in the setting of a multidisciplinary clinic, doctors determine whether the patient will benefit from CyberKnife therapy.
Patients are then implanted with markers — tiny gold seeds — that serve as reference points for targeting the exact location of the tumor during treatment. Insertion is most often accomplished with the aid of CT guidance. Occasionally, when patients undergoing surgery are deemed inoperable, gold markers are immediately placed while they are still in the operating room.
Patients must also be fitted with a special custom-molded body cradle that conforms to the body. This makes treatments more comfortable and ensures the body’s position is the same during every treatment. The patient also wears a special vest that allows the robot delivering the radiation to link up chest motion and breathing positions with the position of the tumor. The vest, along with constant imaging of the gold markers, generates data that allows the robot to closely follow the tumor’s motion as the radiation is delivered. While the patient is in the cradle, a CT scan is used to define the exact size, shape and location of the tumor.
Next a treatment plan is designed to determine dosage to identify nearby areas where radiation must be minimal. The treatment is usually completed in three sessions of up to two hours each. During treatment, the robot moves around the patient’s body to deliver radiation in various locations. The robot stops at each location. As the treatment is being delivered, the robot essentially breathes along with the patient.
Q. What side effects may be associated with CyberKnife liver cancer treatment?
Early results indicate that most liver cancer patients tolerate CyberKnife treatments well and that their liver function is not affected. Common side effects may include fatigue and nausea. The treatment itself is pain-free. Patients are advised that their tumors will not disappear and that it could take months to determine the effectiveness of the treatments, which includes stability of the treated tumor.