Hi, Jo:
Speaking from personal experience, CyberKnife (CK) is an outstanding choice for treatment. And seeing that your symptoms are worsening, it makes sense that you should now seek treatment in order to prevent further deterioration. Here's some information that will kickstart your research on CK (comparing it to GammaKnife [GK] radiosurgery):
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 over 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.)
Speaking personally, I had CK performed almost 5 years ago. My tumor has shrunk over 70% since treatment and I've regained around 80% of my previously lost balance. I've had moderate midrange and high-frequency hearing loss (up to 25 dB) on my AN side since getting treated but still have useful hearing in that ear. My tinnitus decreased dramatically immediately following CK and is, on most days, around 90% lower in volume compared to what it sounded like pre-treatment. Your mileage will almost certainly vary, as each person's response to treatment is different. I don't know what your other symptoms are, if any. But the degree to which my tumor shrank and the positive changes in my balance function and tinnitus level are extraordinary, so you shouldn't expect the same. On the other hand, at least a few other forumites have had similar results, while others have had better hearing preservation than I.
Best wishes,
TW
