Cyberknife Radiation Therapy

The challenge that doctors face in treating prostate tumors with radiation therapy is that the prostate moves unpredictably as air passes through the rectum and as the bladder empties and fills. Minimizing any large movements of the prostate can help reduce unnecessary irradiation of surrounding healthy tissue. The CyberKnife Robotic Radiosurgery System is able to overcome this challenge by continuously identifying the exact location of the prostate and making active corrections for any movement of the prostate throughout the course of the treatment. During treatment, a patient lays still and breathes normally while the CyberKnife zeroes in on a moving target – the prostate – and irradiates it without harming surrounding areas. As a result, the procedure is more comfortable for patients, radiation is delivered more accurately and treatments can be completed in four to five days.

Currently the CyberKnife Radiosurgery System is most frequently used by itself for patients with early stage prostate cancer confined to the prostate or in combination with another therapy, such as external beam radiation for patients with disease that extends beyond the prostate. Depending on the stage of the patient’s prostate cancer the doctor will recommend a treatment plan.

Over a dozen clinical experiences have been published to date on CyberKnife prostate SBRT. At 5 years after treatment a recurrence-free rate of 93% has been reported. Recurrence-free rates of 100% at 44 months, 97.5% at 51 months, and 94% at 4 years [48] have also been reported. Toxicity has been quite low; rates of grade 2-3 toxicity at 20-60 months after treatment range from 2-10% for urinary toxicity and 0-5% for bowel toxicity. Erectile dysfunction has ranged from 60% at 35 months for an early experience to 13-40% at 1.5-3 years for more recent experiences in which the prostate gland is delineated with the aid of MRI which typically reduces the volume of the region exposed to radiation.