Phoenix Cyberknife and Radiation Oncology Center


This document is intended to answer some of the frequently asked questions about CyberKnife®prostate SBRT (Stereotactic Body Radiotherapy)*

Is the CyberKnife system cleared by FDA?

Yes. In 2001 the CyberKnife System received 510K clearance from the U.S. Food and Drug Administration (FDA) to treat anywhere in the body where radiation is indicated, including the prostate. CyberKnife treatment is often referred to as SBRT or Radiosurgery.

Why, and what does that mean?

SBRT stands for Stereotactic Body Radiation Therapy. SBRT and Radiosurgery (also known as SRS) are techniques used in Radiation Oncology to ablate (destroy) diseased tissue, often malignant tumors, by precisely directing very high doses of radiation at the diseased tissue while avoiding surrounding normal tissue as much as possible. Unlike conventional radiation therapy, SBRT and SRS treatments are given over a small number of treatment sessions, usually between 1 and 5. The CyberKnife System was specifically designed to perform SRS and SBRT treatments with high degrees of accuracy. The CyberKnife System takes images continually throughout each treatment session to ensure that the radiation beam is aimed at the target. If any motion of the target is detected by these images, the CyberKnife System can precisely adjust the position of the radiation beam under robotic control to keep it on target and away from normal tissue. SRS is typically used to describe treatments specific to the head and neck, while SBRT commonly refers to treatments anywhere else in the body.

What is CyberKnife Prostate SBRT?

Despite its name, the CyberKnife System is not a surgical procedure. In fact, there is no cutting involved. Instead, the CyberKnife System delivers high doses of radiation directly to the prostate cancer over a 4 to 5 day period. Each of these treatment sessions is called a "fraction." The CyberKnife System is a linear accelerator mounted to a robotic arm that is specifically designed to deliver stereotactic radiation from hundreds of different angles. Given this robotic maneuverability, less healthy tissue is affected and higher doses targeting the prostate can be delivered exactly where it counts most. The prostate gland can move unpredictably throughout the course of treatment, this makes the ability to track, detect and correct for motion critically important. The CyberKnife System continually tracks and automatically corrects for the movement of the prostate in real time. This enables the system to correct the beam direction so that it is focused on the prostate throughout the entire treatment. The robot constantly monitors and aligns the real time location of the prostate to ensure any adjustments in the beam delivery match the prepared treatment plan while automatically correcting for any movement during a treatment by relaying critical logistical information to the system software. Safety mechanisms are in place to ensure that the beam of radiation is 'locked on' to the intended target should the prostate move out of acceptable range.

What are the benefits of CyberKnife prostate SBRT?

CyberKnife SBRT provides an alternative to conventional radiation therapy and to surgery, including da Vinci® robotic surgery for organ confined prostate cancer. Unlike surgery which is invasive and typically requires general anesthesia and hospitalization for 1 to 3 days, CyberKnife prostate SBRT is noninvasive and is performed on an outpatient basis. The risks that are often associated with prostate surgery, such as infections, bleeding, pulmonary complications, and death are avoided by the noninvasive nature of CyberKnife prostate SBRT. Unlike the 6-8 weeks of conventional radiation therapy treatment, treatment is typically completed over a week in 4-5 short outpatient treatment sessions and most patients continue with their normal daily activities throughout treatment. There is typically little to no recovery following CyberKnife prostate SBRT as opposed to surgery which requires patients to go home with a urinary catheter and to endure several weeks to months of post-surgical recovery. CyberKnife prostate SBRT's accuracy enables sparing of normal tissues surrounding the prostate, maximizing the preservation of quality of life for patients.

What is the typical follow-up schedule after CyberKnife prostate SBRT and how does this compare to the follow-up after prostate surgery?

Follow-up procedures after surgery or after CyberKnife SBRT are typically quite similar. These could include periodic office visits and PSA testing. Post treatment imaging is typically not required for patients with organ confined prostate cancer after treatment, but this practice may vary depending on specific physician practices. The frequency of PSA testing will vary according to your physician and your results of previous tests. Following prostate treatment, PSA typically falls to zero immediately, often consistent with a successful treatment and patients are monitored to detect any new PSA levels that may indicate prostate cancer recurrence. Following CyberKnife prostate SBRT, PSA levels typically decline continuously following treatment and reach very low levels over a 1-to 2- year period that are often indicative of a successful treatment. For both prostate surgery and CyberKnife prostate SBRT, PSA is monitored typically for 5 years after treatment to ensure there is no rise in measured levels that may be consistent with cancer recurrence. Patients for both treatments are also assessed at each follow-up for any potential side effects that they may be experiencing.

What are my treatment options after CyberKnife SBRT, if the cancer returns?

Am I still a candidate for radiation therapy or surgical treatment? Although less than 10% of patients have a recurrence of their prostate cancer within the first 5 years of treatment following CyberKnife prostate SBRT, it is important to understand the options available should a recurrence be detected. Recurrences following CyberKnife prostate SBRT, prostate surgery or following conventional radiation therapy may all occur either within the region of the prostate or prostate resection area or outside of this area in another region of the pelvis or body. Because of the CyberKnife System's highly accurate delivery and small treatment margins sparing surrounding normal tissues, retreatment by either radiation therapy and/or surgery is possible following CyberKnife prostate SBRT if it is determined that the recurrence is within the prostate. Since recurrences are uncommon, and since they may occur outside of the prostate, treatments available to each patient will vary. Each case is typically evaluated by clinicians, taking into consideration a patient's specific clinical picture and disease pattern to determine the best plan for retreatment specific to a patient's individual needs.

Does CyberKnife have long-term data supporting its use?

Yes. Below is a link to the published studies:

What option is right for me to cure my prostate cancer?

As each patient is different, so is his prostate cancer. And although there are a number of effective treatment options such as surgery, conventional radiation therapy, and CyberKnife prostate SBRT, there is a lack of comparative evidence and studies comparing outcomes of current technologies and treatments. We encourage you to talk to your physician so you can decide on what treatment option is best for you.

*References for these statements can be found in the table above

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3. King CR, Brooks JD, Gill H, et al. Long-Term Outcomes from a Prospective Trial of Stereotactic Body Radiotherapy for Low-Risk Prostate Cancer. Int J Radiat Oncol Biol Phys 2012;82:887-882.
4. Freeman DE, King CR. Stereotactic body radiotherapy for low-risk prostate cancer: five-year outcomes. Radiat Oncol 2011;6:3.
5. Jabbari S, Weinberg VK, Kaprealian T, et al. Stereotactic Body Radiotherapy as Monotherapy or Post-External Beam Radiotherapy Boost for Prostate Cancer: Technique, Early Toxicity, and PSA Response. Int J Radiat Oncol Biol Phys 2012.
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17. Krambeck AE, DiMarco DS, Rangel LJ, et al. Radical prostatectomy for prostatic adenocarcinoma: a matched comparison of open retropubic and robot-assisted techniques. BJU Int 2009;103:448-453.
18. Yee DS, Ahlering TE, Gelman J, et al. Fossa navicularis strictures due to 22F catheters used in robotic radical prostatectomy. Jsls 2007;11:321-325.
19. Murphy DG, Kerger M, Crowe H, et al. Operative details and oncological and functional outcome of robotic-assisted laparoscopic radical prostatectomy: 400 cases with a minimum of 12 months follow-up. Eur Urol 2009;55:1358-1366.
20. Ham WS, Park SY, Rha KH, et al. Robotic radical prostatectomy for patients with locally advanced prostate cancer is feasible: results of a single-institution study. J Laparoendosc Adv Surg Tech A 2009;19:329-332. 21. Pardo Y, Guedea F, Aguilo F, et al. Quality-of-life impact of primary treatments for localized prostate cancer in patients without hormonal treatment. J Clin Oncol 2010;28:4687-4696.
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23. Ahlering TE, Eichel L, Skarecky D. Evaluation of long-term thermal injury using cautery during nerve sparing robotic prostatectomy. Urology 2008;72:1371-1374.
24. Fuller D, Shirazi R, Naitoh J, et al. Virtual HDR SBRT for localized prostatic carcinoma: Efficacy and quality of life assessment. Int J Radiat Oncol Biol Phys 2011;81:S423-S424.
25. Suardi N, Ficarra V, Willemsen P, et al. Long-term biochemical recurrence rates after robot-assisted radical prostatectomy: analysis of a single-center series of patients with a minimum follow-up of 5 years. Urology 2012;79:133-138.
26. American Cancer Society, 2011 For more information on CyberKnife Prostate SBRT visit
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