Hi, Muru:
In answer to your question:
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, but this is not a factor in your case because you already have 95% hearing loss on your AN side.
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.)
Both UPMC and Stanford are very highly regarded. You can probably do no better than to go to one of these fine facilities, and you are wise to make the extra effort to do so, as the outcome of your treatment will impact your quality of life going forward and both UPMC and Stanford have outstanding track records. Drs. Chang and Gibbs treated me at Stanford, and I had phenomenally good results. I cannot say enough good things about Dr. Chang. He is 100% dedicated to his patients and had treated over 700 AN patients with CK at the time I was treated 41 months ago. I imagine by now he has probably treated over 1000 patients, as he treats over 100 per year; that's around 2 AN patients per week! When it comes to brain surgery (including radiotherapy), practice makes perfect, and Dr. Chang has had a ton of practice.
Best wishes,
TW
