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Radiosurgery of the Prostate
Radiosurgery of the Prostate
Radiosurgery has been around since 1949, when a neurosurgeon and radiobiologist collaborated to utilize protons from a cyclotron to treat brain tumors noninvasively. Less than 20 years later, the GammaKnife was developed to ablate tumors in the spine, as well as in the brain, as a pain-free alternative to traditional open surgery.
Newer technology introduced since the turn of the century, such as the CyberKnife Robotic Radiosurgery System, is now used to destroy tumors and lesions anywhere in the body, including those in the lungs, breast, pancreas, liver, kidneys and prostate. The key is proven technology that can target, with pinpoint precision, tumors that move with normal body functions such as breathing.
In the last five years, CyberKnife radiosurgery has been introduced in practice for treating prostate cancer. Ideal candidates are patients with low/intermediate risk prostate cancer, i.e., a PSA less than 10 ng/mL and a Gleason score of a 3 + 4 equals 7 or less. Age or co-existing medical conditions do not affect eligibility.
Prior to the planning stage for treating prostate cancer, fiducial markers are inserted into the prostate in an outpatient procedure. The patient is fitted for a special body cradle molded out of soft material to the patient’s body to ensure body position is the same for each treatment session.
During the planning stage, a CT scan of the patient while in the body cradle is taken to identify the size, shape and location of the tumor. The scanned image is then transferred to the CyberKnife system where areas to be treated and critical areas to be avoided, such as the rectum, bladder and nerves that control erection, are outlined and programmed into the system. This minimizes damage to these areas and to healthy tissue surrounding the tumor site and reduces side effects.
During treatment, the patient, breathing normally and listening to music, lies comfortably in the body cradle on the treatment table. The location of the prostate as it moves is continually tracked and detected, so that radiation is precisely delivered to it.
The total radiation dose used in CyberKnife radiosurgery is similar to and often higher than that used in traditional radiation therapy. It is the delivery of the radiation that is different. Traditional radiation therapy delivers the dose from 1 to 5 different angles; whereas, the CyberKnife delivers it from up to 1200 different angles almost 360 degrees around the tumor. Because the radiation is divided into up to 1200 individual beams, each beam is a very low dose near surrounding tissue and causes no damage. At the focal point of the tumor site, however, the beams converge with submillimeter accuracy. The result is optimal ablation and destruction of the tumor with minimal side effects.
Another advantage for the patient is a reduction in the number of treatment sessions. Traditional radiation treatment for prostate cancer is typically 5 days a week, Monday through Friday, for 6 to 9 weeks totaling up to 45 individual sessions. With the CyberKnife radiosurgery, a patient can be treated in only 5 individual sessions. Treatments are done on an outpatient basis and last one hour. Afterward, patients immediately return to their normal activities.
Outcomes are good. Results from our clinical trials have demonstrated reductions in PSA levels with low rates of mild side effects during short-term follow-up after treatment. Data is still being collected to evaluate long-term cures and toxicity. Currently, patient outcomes are exceeding expectations. We are cautiously optimistic regarding the role of radiosurgery in the role of treating urologic cancers.
Dr. Lee Ponsky is director, Urologic Oncology Center, University Hospitals Urology Institute, UH Case Medical Center, and the Leo & Charlotte Goldberg Chair in Advanced Surgical Therapies, UH Case Medical Center. He is also Associate Professor, Case Western Reserve University School of Medicine.
MD News March/April 2012, Cleveland/Akron/Canton