Cyberknife

CyberKnife robotic radiation treatment machineCyberknife is a type of robotic radiation therapy machine.  It is different from normal radiation machines in the following ways:

  1. The machine continuously tracks the location of the marker seeds in the prostate gland during the treatment session.  If the prostate moves, the radiation beam moves.
  2. Cyberknife can only treat small areas.  The prostate gland is small enough for this treatment.  However, cyberknife is not able to treat larger areas like the lymph gland chains in the pelvis.
  3. Cyberknife gives a very high dose each treatment, for a total of up to 5 treatments.  It more or less indiscriminately damages everything in its target zone, hence the “knife” name.  Cyberknife  is a form of radiosurgery.  Radiosurgery was originally invented to destroy small brain tumors without having to crack open up the skull.

Normal radiation therapy machines are more versatile.  They can treat larger areas, for instance they can treat massive prostate glands and can they include areas outside the prostate such as the lymph node regions in the pelvis if desired.  The radiation therapy can be given at a traditional slow daily rate over many days which gives the healthy tissues a chance to heal themselves.

The robotic tracking of the marker seeds is an impressive feature.   With cyberknife, because potentially destructive high daily doses are used, the robotic tracking is required to ensure that the rectum or bladder do not move into the target zone.

The shorter treatment duration of Cyberknife is very enticing.  It is a newer technology, so there have not been any long term results published yet.  However, the daily radiation treatment dosages are similar to the ones that we have used with HDR brachytherapy.  For example, this study with pretty much the longest follow-up available of 5 years looked at only 41 patients, and all the patients had early stage low risk prostate cancer. The results look very good.  More and more insurance plans are covering Cyberknife for prostate cancer as they recognize the shorter treatment time benefits and the very good results.

Summary

  1. Cyberknife uses 5 high dose treatments that kill both cancerous cells and healthy cells within the target zone.
  2. Because of this, treatments must be highly targeted and to a small area.
  3. There are not many clinical results available yet.

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