Hi, Sonia:
"Radiosurgery" is a general term to describe radiation treatment applied in one dose (such as with the GammaKnife procedure). "Radiotherapy" refers to fractionated radiation treatments; that is, radiation treatments that are split up into multiple, smaller doses (so that the body doesn't get too harsh of a dose all at once). Radiotherapy typically refers to "fractionated stereotactic radiation," or FSR. In plain English, this means the head is held in position so that it can receive radiation (divided into small doses spread 24 hours or more apart) accurately targeted at the tumor. CyberKnife is a form of FSR that is pretty broadly regarded as the most accurate; accuracy is important, as it minimizes collateral damage to healthy tissues. GammaKnife offers roughly the same degree of accuracy as CK.
I posted a comparison of the different types of radiation treatments here:
http://anausa.org/forum/index.php?topic=6670.0Following (in quotes) is an excerpt from my post, in case you don't want to read the entire thread:
"As for radiosurgery, GammaKnife (GK) and CyberKnife (CK) are both more accurate than standard FSR (fractionated stereotactic radiation) such as Novalis. CK is also a form of fractionated radiotherapy, but its accuracy gives it a leg up on standard FSR.
CK delivers a more homogeneous dose to the tumor compared with GK. CK delivers only 15% higher dose to the center of the tumor than at the periphery, whereas GK delivers fully double (100% greater) dose at the center compared to at the periphery. CK advocates believe that GK's higher dose at the center of the tumor increases the chance of damage to nearby healthy tissue. Also, GK delivers one large dose to the tumor because one treatment is all you can do with GK (this is because a ring is fitted to your head for the treatment and, once it's removed, there's no way to get it exactly in the same place for a second treatment). With CK, on the other hand, a thermoplastic mask is custom-fitted to your head and the tumor's location (in relation to the mask and your bony structures) is plotted into the computer; on followup visits for treatment, they put the mask on your head again and you're ready for the next dose. This flexibility allows CK to apply smaller doses to the tumor than GK with each treatment; together, the smaller doses add up to the same total biologically equivalent dose as you would get with GK's one and only treatment, but (theoretically, at least) the hearing nerve and other healthy tissue has time to recover in between treatments (whereas the tumor supposedly doesn't recover as quickly). Presumably due to the fractionating of dosage, studies show CK yields slightly better results at preserving hearing compared with results for GK. Furthermore, GK's ring is screwed into the head (the screws stop at the skull) to keep it stationary (so that the radiation stays focused on the tumor), a mildly invasive procedure. CK is totally non-invasive: a series of overhead X-rays tracks the patient's head movements and tells the computer-controlled CyberKnife machine which way to move to track any small movements the patient may make so that the radiation stays centered on the tumor. GK advocates say that's all well and good, but GK has about 40 years of track record, whereas CK has been around a lot less time and is not as proven of a treatment as GK. (CK was approved by the FDA in 1999, although Stanford University Medical Center has been using it since 1994 in clinical trials because their Dr. Adler invented CK.)
The best advice I can give you is shop around for the right treatment/doctor/facility for you and get at least 2 or 3 opinions (I got 6!). Develop a list of questions you want to ask each doctor you see, and interview the heck out of them. After awhile, you will know in your heart what is the best path for you personally to take."
Best wishes,
TW