CyberKnife Treatment

CyberKnife Treatment Prostate Cancer

CyberKnife Treatment Prostate Cancer. CyberKnife is a trademarked name for a machine designed to deliver stereotactic body and head radiosurgery. It consists of a linear accelerator mounted onto a robotic arm. It can deliver small pencil thin beams of radiation. Radiosurgery typically involves treatment of very small areas of tissue. Radiosurgery , as well as the CyberKnife were first developed exclusively to treat small brain tumors and other abnormalities of the brain. Radiosurgery to the brain can now be delivered using machines such as Gamma knife, and Linear accelerator based radiosurgery. With current linear accelerator technology, all of these systems are relatively equivalent in their ability to deliver precise radiation treatment to small areas and limit dose to surrounding normal brain tissue. The CyberKnife has recently been used to treat prostate cancer. It involves treating the prostate with 5 fractions of high dose radiation. Although it has been marketed as a unique form of radiation, it is not. It is a form of hypofractionated photon beam radiation therapy. Hypofractionation means delivering radiation therapy in a shorter period of time with fewer than standard number of fractions using relatively high doses per fraction. For example hypofractionated radiation for prostate cancer using the CyberKnife usually involves treating with dose fractions of 700 or 800 cGy for a total of five fractions. This is in contrast to standard radiation which usually involves doses of 180 to 200 cGy per fraction given for a total of 45 fractions. Hypofractionated radiation can be delivered using the CyberKnife, as well as commonly available linear accelerators that employ intensity modulated radiation therapy (IMRT) as well as image guided radiotherapy (IGRT). The CyberKnife offers no advantage over these more commonly available treatment machines. The radiation treatment is completely painless and non-invasive. During treatment, the most commonly reported side effects are slight fatigue and having to go to the bathroom more frequently. You should NOT develop any nausea, abdominal pain or loss of hair on your head. You will NOT lose your ability to control your bowels or bladder. You will be able to continue working full-time and should enjoy all of your regular activities.

Hormone Blocking Therapy

Prostate cancer typically feeds on testosterone, the male hormone. A combination of a shot (Lupron or Zoladex) that you receive every few months from your Urologist, and pills (Flutamide or Casodex) that you take daily can temporarily block all of the testosterone in your body. By cutting off the “food supply” to the cancer, several helpful things happen:

  • After a few months, your prostate will shrink 30-40% in size. In men with large prostate glands, it becomes easier to distribute the seeds for the implant and fewer seeds are required. An added bonus is that you will probably notice that it is easier to urinate because your prostate is smaller.
  • Some cancer cells outside the prostate may actually die, or “starve to death.”
  • The remaining cancer cells can be made more sensitive or vulnerable to the upcoming radiation and thus more likely to be killed.

While hormone-blocking treatment alone will not permanently rid the body of the cancer, it has been shown to improve cure rates with radiation in men with more advanced stage cancer. It also has the ability to make the seed implant procedure possible in men with very large prostates that would have otherwise been technically too difficult to implant. When administered, men typically take the hormone blocking treatment for two to three months before beginning radiation, and continue the treatment until after the seed implant. Common side effects from the hormone blockers include temporary hot flashes, fatigue, and loss of libido.