CyberKnife® FAQs


CyberKnife® is targeted, high-dose radiation administered to the cancerous prostate tumor over a series of 1-5 sessions and days. Patients are awake during each 30-90 minute treatment. The radiation used in CyberKnife® treatments is referred to as Stereoactic Body Radiation Therapy (SBRT) and is recommended for men diagnosed with low to moderate risk prostate cancer.


Radiosurgery and radiation are “best guess” treatments that attempt to address all cancerous prostate cells. During CyberKnife® therapy, radiation is directed at the cancerous prostate based on pre-treatment biopsy and CT scan data. Imaging information gathered before and during the procedure is used to approximate the radiation dosage based on the location, size, and shape of the tumor.

However, pre-surgery prostate cancer data is not always accurate. Due to limitations in prostate cancer staging diagnostics, the true nature and scope of a man’s tumor is not known until it is visualized during surgery. In these post-surgery tests we learn the exact type of prostate cancer, how extensive it is, as well as the status of the seminal vesicles and lymph nodes. Research shows that prostate cancer tumor staging actually changes in as many as 40% of men after post-surgery lab testing.

Men who choose CyberKnife® radiation will be left with a fluctuating PSA level and non-specific tumor results. After CyberKnife® therapy the tumor can take months or years to disappear, or it may remain in the body permanently with stalled growth. A rigorous follow-up schedule must be maintained to monitor PSA level and tumor status for life. While the hope is that the cancer will not return, the testing and worry can be very draining.

According to CyberKnife® research, 84% of patients chose the treatment method because of their comfort with the expected risks and side effects, but only 59% of men believed the procedure was the most likely to eliminate their prostate cancer.


CyberKnife® Robotic Radiosurgery is not robot-assisted surgery; it is simply another form of prostate cancer radiation such as external beam radiation therapy (EBRT) or brachytherapy. CyberKnife® is FDA-approved radiation therapy for the treatment of cancer, though the procedure is very new.

During robotic prostatectomy surgery, Dr. Samadi uses real-time, first-hand visualization to assess the prostate cancer scope and remove the tumor. This proven, minimally invasive procedure integrates the precision and visualization of robot-assisted surgery with the expertise of Dr. Samadi’s vast surgical background. With appropriate follow-up and post-surgery care, PSA level should drop to an undetectable level after robotic prostatectomy surgery.

Radiation such as CyberKnife® can be an effective secondary measure for men with high-risk, recurring prostate cancer


The negative side effects of CyberKnife® can be expected to mirror those of other targeted radiation therapies.

Over the short term, radiation therapy for prostate cancer can cause:

  • Urination problems including burning and blood in the urine
  • Urinary urgency and frequency
  • Weakened urinary stream
  • Incomplete emptying of the bladder
  • Anal and rectal irritation, rectal bleeding, hemorrhoids, and stool problems
  • Fatigue and nausea

Long-term CyberKnife® and prostate cancer radiation side effects may include:

  • Sexual impotence and/or erectile dysfunction for up to 2 years after treatment
  • Delayed orgasm or ejaculation
  • Temporary or permanent reduction in sperm count; fertility should be discussed with your physician prior to CyberKnife® treatment
  • Impaired bowel function
  • Potential increased risk of bladder or rectal cancer by 5%


Most patients with lower-risk prostate cancer have very positive results after radiation. Your ongoing PSA testing and tumor monitoring will watch for any changes or developments in your prostate cancer. If needed, CyberKnife® therapy can be repeated. Robotic prostatectomy surgery provides greater peace of mind, as the tumor is removed and the PSA should reach an undetectable level.


If your prostate cancer returns after radiation therapy, it is extremely challenging to perform a successful prostatectomy procedure due to physical alterations caused by the targeted radiation. While Dr. Samadi is highly skilled in performing such operations, relying on CyberKnife® Radiosurgery as an initial prostate cancer treatment may severely limit secondary treatment options if the cancer returns. Radiation for prostate cancer is best reserved as a secondary option should the cancer return.

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