Prostate Cancer

The CyberKnife robotic radiosurgery system is a widely used form of nonsurgical prostate stereotactic body radiation therapy (SBRT). The American Society for Radiation Oncology (ASTRO) believes that enough clinical evidence exists so that SBRT should be considered an appropriate alternative for select patients with low- to intermediate-risk prostate cancer.

What is CyberKnife?

CyberKnife is a non-invasive prostate cancer treatment technology in which high-dose radiation is delivered to the tumor from a linear accelerator mounted on a highly maneuverable robotic arm. Hundreds of angles and beam width adjustments in the CyberKnife prescribed treatment plan enable the radiation to be contoured to the shape of the prostate. This results in treatment aimed directly to the prostate gland, avoiding nearby critical anatomy. This precision reduces treatment time to just five outpatient visits. In comparison, conventional radiation therapy could require up to 45 visits.

How does it work?

About two weeks prior to treatment, patients are scheduled for a short outpatient procedure in which three to five tiny gold seeds (called fiducials) are inserted into the prostate. The fiducials guide the CyberKnife System to track the tumor during the treatment process. The following week, the patient is fitted with a custom body support pad to help maintain a relaxed and still position.

During the treatment, the patient wears comfortable clothing and will lie on the treatment table as the CyberKnife’s computer-controlled robotic arm moves quietly around the patient, delivering radiation directly to the tumor. The procedure is done in a series of five or fewer outpatient visits. It is painless and does not require sedation. The patient is able to communicate and be seen by the technologists during the entire procedure.

After treatment is complete, most patients immediately return to their normal activities.

What are the risks and side effects?

Most patients experience minimal to no side effects. Because the CyberKnife was designed to avoid healthy tissue and critical anatomy, it reduces side effects regarding quality of life – such as sexual, urinary, and bowel function. The CyberKnife treats at a higher per-fraction dose given its superior accuracy over conventional radiation therapy. Fewer treatment visits result in minimal interruption to work, family, and hobbies.

How effective is it?

The efficacy outcomes of CyberKnife treatment for prostate cancer have been comparable to other treatment outcomes at five years. Certain outcomes, such as bladder incontinence, have been greatly improved with the CyberKnife treatment as compared to surgery and other invasive prostate treatments. Follow-up with the radiation oncologist and primary care or urologist will involve measurement of serum prostate specific antigen (PSA) levels, which is the best measure of disease control. PSA levels may change, but over time the patient can anticipate the levels to trend lower or decrease, indicating that the prostate cancer has been ablated by the high-dose radiation.

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