CyberKnife Therapy for Lung Cancer
» What is CyberKnife and how can it be used to treat lung cancer?
» When was CyberKnife approved to treat lung tumors?
» What are CyberKnife's advantages for lung cancer treatment?
» How effective is CyberKnife in the treatment of lung cancer?
» What is the process involved in receiving CyberKnife therapy for lung cancer?
» What side effects may be associated with CyberKnife lung cancer treatment?
Q. What is CyberKnife and how can it be used to treat lung cancer?
CyberKnife is a robotic radiation therapy machine. It was originally developed as a device for Stereotactic Radiosurgery (SRS) for tumors of the brain. It is now approved to treat tumors anywhere in the body, including the lung.
Stereotactic radiation therapy is a radiation treatment technique in which high doses of radiation are delivered using very precise beams or a moving beam of radiation focused on the tumor. The beam or beams are very narrow, so that a very high amount of radiation is delivered to a precise area in the lung. The aim is to use such a high dose that the tumor is destroyed, while sparing healthy tissue. The radiation from the CyberKnife machine is the same type used in standard external beam radiation machines.
Q. When was CyberKnife approved to treat lung tumors?
CyberKnife was cleared by the U.S. Food & Drug Administration in 2001 to treat tumors anywhere in the body, including the lungs.
Q. What are CyberKnife’s advantages for lung cancer treatment?
CyberKnife is appropriate for patients who cannot undergo lung cancer surgery due to their weak medical condition, or who don’t want to undergo surgery. It is a non-invasive alternative treatment for lung cancer with no surgery involved.
One major challenge to treating lung cancer is that the tumors move as the patient breathes. With CyberKnife, that problem is minimized and patients can breathe normally during the treatments. CyberKnife treatments are usually performed on an outpatient basis over one to five days. No overnight stays are required. Fewer treatments are required compared to conventional radiation therapy due to the higher dosage per treatment.
Q. How effective is CyberKnife in the treatment of lung cancer?
Surgery is generally the treatment of choice for patients with early stage lung cancer who are medically fit for surgery. Conventional radiation therapy is an alternative for patients who are not medically fit for surgery, but the probability of local tumor control is only 40 percent and the five-year survival rate only 16 percent in patients treated with this standard method of radiation therapy.
CyberKnife is a refined method of Stereotactic Body Radiation Therapy (SBRT) that allows precise tracking of tumors that move with respiration. In 2006, an early paper published by investigator Hiroshi Onishi, MD, showed very promising results for SBRT. Five-year local tumor control was 86 percent for those patients treated with a high-dose SBRT regimen. A 2009 published report from Karolinska University in Sweden showed 100 percent local control for lung tumors 2 cm or less treated with SBRT; lung tumors between 2 and 3 cm were controlled in 75 percent of cases.
A 2010 report published in the Journal of the American Medical Association showed a 91 percent local control rate for lung tumors up to 5 cm. Three-year survival was 56 percent in these patients, who were medically unfit for surgery, treated with SBRT. A review of 35 studies on SBRT for lung cancer also published in 2010 showed five-year survival of 45 percent and local tumor control of 80 percent. The results from this review suggest that SBRT is at least twice as effective as conventional radiation therapy for early-stage lung cancer in terms of both local tumor control and patient survival.
Q. What is the process involved in receiving CyberKnife therapy for lung cancer?
A team approach is used, involving a surgeon, radiation oncologist, interventional radiologist, a radiation therapist, and other support staff. First, doctors identify the location and size of the tumor. Patients may or may not have to have markers — tiny gold seeds — implanted to help pinpoint the location where the beam will be aimed. The markers are implanted using a tiny needle inserted into the tumor through the chest wall. Insertion is guided by CT scan. The seeds also can be inserted through the patient’s mouth.
Patients are also fitted with a special custom-molded body cradle that conforms to the body. It is used to make treatments more comfortable and to ensure 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 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, live X-ray images pinpoint the exact size, shape and location of the tumor.
Next a treatment plan is designed to determine dosage, and identify areas such as the spinal cord, esophagus, air passages and blood vessels where radiation must be minimal. The treatment usually is completed in one to five sessions. During treatments, the robot moves around the patient’s body to deliver radiation in various locations. The robot stops at each location. Software determines where the radiation should be delivered by correlating breathing motion with the tumor. The robot essentially breathes along with the patient. Treatments take about one hour each.
Q. What side effects may be associated with CyberKnife lung cancer treatment?
Most who undergo CyberKnife treatment for lung cancer experience minimal side effects and recover quickly. Fatigue is the most frequently reported side effect. The treatment itself is pain-free. Patients are advised that their tumors will not suddenly disappear and that it may take months to determine the effectiveness of the treatment.