Doctor discussing treatment with patient at a table

Stereotactic body radiation therapy (SBRT) is a type of external beam radiation therapy in which the radiation therapy is given in five or fewer treatments. Conventional radiation treatment for prostate cancer consists of 39 to 45 treatments. With SBRT, a higher radiation dose is delivered with each treatment compared to conventional treatment.

The Power of CyberKnife

External beam radiation therapy consists of high energy X-rays delivered from a linear accelerator targeting the tumor. The CyberKnife machine at UofL Brown Cancer Center is a lightweight linear accelerator with a robotic arm that delivers radiation to the tumor precisely and accurately. Additionally, the CyberKnife can track the motion of the tumor during the treatment delivery, which allows for a higher amount of radiation to the tumor and less to the surrounding normal tissue.

CyberKnife technology can be used to treat several types of cancer while minimizing side effects for eligible patients including brain, kidney, liver, lung, ocular/orbital, prostate, pancreatic and spinal tumors, as well as metastatic cancer. It is also used to treat acoustic neuroma, arteriovenous malformation and trigeminal neuralgia. For more information about CyberKnife, visit

Let’s take a closer look at using CyberKnife for prostate cancer. 

Prostate cancer patient eligibility

Talk to your doctor to see if you might be eligible for SBRT using CyberKnife. Prostate cancer patients eligible for SBRT using CyberKnife include men with the following:

  • Gleason ?3 + 4 = 7, less than 50% biopsy cores containing cancer, PSA < 10 ng/ml, clinical stage T2a or less
  • Gleason 3 + 3 = 6, less than 50% biopsy cores containing cancer, PSA < 20 ng/ml, clinical stage T2a or less
  • Gleason 3 + 3 = 6, less than 50% biopsy cores containing cancer, PSA < 10 ng/ml, clinical stage T2b or T2c

Technology to reduce side effects

To further increase the accuracy and reduce the side of effects of prostate SBRT, prior to the treatment fiducial markers are placed in the prostate. The purpose of these markers is that they appear bright white on x-ray images taken during SBRT. Therefore, the CyberKnife machine can accurately determine the location of the prostate prior to delivering the radiation treatment.

Additionally, a SpaceOAR hydrogel is inserted in the space between the prostate and the rectum. The purpose of the SpaceOAR is to separate the prostate from the rectum, thereby reducing the radiation dose to the rectum and decreasing rectal side effects. The SpaceOAR is biodegradable and will degrade after approximately six to 12 months.

PSA levels after treatment

Following any type of treatment for prostate cancer, the PSA is checked at regular intervals. After prostatectomy, the PSA should be zero since the prostate has been completely removed. After any type of radiation treatment, the prostate may still make some PSA, but should be within the normal range (< 4 ng/ml). After SBRT for prostate cancer, the chance that the PSA will drop and remain within normal limits is 92 percent at five years after treatment and 88 percent at 10 years after treatment.

Side effects of SBRT with CyberKnife for prostate cancer

Regarding the side effects of SBRT with CyberKnife, there is a 20 percent chance of having to be placed on a medication, such as Flomax, to help with urinary symptoms, including weak stream or waking up at night to urinate. There is a 1-2 percent chance of needing a urinary catheter or a procedure because of blocked urinary flow. There is a 1 percent chance of having bleeding from the rectum.

Ask your doctor if you might be eligible for treatment using CyberKnife or ask the experts at UofL Brown Cancer Center for a second opinion. Call 502-562-HOPE (4673).

Visit to learn more about CyberKnife at UofL Brown Cancer Center.

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Article by:

Scott Silva, M.D., Ph.D.

Scott R. Silva, M.D., Ph.D. is a radiation oncologist at UofL Health – Brown Cancer Center. He graduated from medical school at the University of Kentucky and completed his residency training in radiation oncology at Loyola University in Chicago. He specializes in genitourinary cancers and has an interest in using brachytherapy in the management of cancer.

All posts by Scott Silva, M.D., Ph.D.
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