For those interested in Gamma knife or Cyberknife, here is an exchange between a patient and Dr. Medberry from the Cyberknife patient support board that I thought would be of value. The patient has a meningioma as opposed to an AN, but the treatments are very similar and the machine issues pretty much the same.
PatientI'm on watchful waiting currently for the residual cavernous sinus meningioma left over from the partial resection of my 4 cm tumor in Feb. 2005. The 6 month followup MRI showed tumor still lurking along the 5th cranial nerve in Meckel's Cave. Both my NS in TX (where I live) and in CA (where resection was done) want to wait, and if there's growth, they are recommending Gamma Knife. I'm already thinking ahead about this, and wondering about Cyberknife vs Gamma Knife for me.
I've poured through this site and now know a LOT about the differences between GK and CK, and believe that CK would be a better bet for me, but I wish the docs who do it had 20+ years of procedural history under their belts, like the docs who do GK. And so, since CK is much newer, I'm concerned not only about the longterm stats for patients who get CK, but also I'm thinking there could be MAJOR differences in the overal experience and expertise of doctors/facilities that do CK around the country. Here in Austin, a facility JUST opened, and clearly I would not want to go THERE.
Since Dr. Chang is among those doing this the longest, I'm wondering if he could weigh in on this.
Thanks SO much for this site.. it's absolutely wonderful to be able to get info this way.
Abby
Dr. MedberryHopefully Dr. Chang will see your post and respond
Here are some observations:
1. Although there is 20 years or more experience with the GK, that does not mean that the center that treats you or the physicians operating it have 20 years of experience. In fact, except in Pittsburgh or U of VA, they don't.
2. Radiation from a GK (gamma rays) and from a CK (x-rays or photons) do not interact differently with tissue or have different biologic effects. THe only issue is targeting. There is abundant evidence that CK targeting is at least as accurate as GK. THerefore, if the dose and fractionatioin are the same, the effects are going to be the same.
3. A significant fraction of the physicians using the CK for intracranial disease have previous experience with the GK. For instance, we have operated a GK for 9 years and a CK for 2.5. We do not feel that our decision making or treatment parameters are any different for the CK except that we have the ability to fractionate treatment. How advantageous that is, I don't know, although we anecdotally feel that we have been able to treat some things on the CK by fractionating the treatment that would have been difficult or impossible or at least extremely hazardous on the GK. That does not, however, constitute real scientific information.
4. Treatment on the CK is usually to a higher isodose line. In layman's terms, what that means is that the dose in the tumor is more homogeneous, with fewer and smaller hot spots. Whether that is advantageous is unknown, although it corresponds more with our decades long standard for treatment with radiation.
THe team at Baylor has both CK and GK, as do the ones at Barrows (Phoenix), Menorah (Kansas City), St. Anthony (Oklahoma City) and probably some others. If you are on the fence, you might want to pick a team that has both options available. If yoiu look on accuray.com, you can find a complete list of sites and some quick research may allow you to refine/expand the list of centers with both instruments available. At St. Anthony we present all such cases in a conference and discuss all the options and try to make a decision that will offer the patient the best treatment, frequently coming to the conclusion that either system would be appropriate. I would not be surprised to find that other centers do something similar.
Clinton A. Medbery, III, M.D.
St. Anthony Hospital Cyberknife Center
Patient
I'm grateful for your generous and extremely informative reply, Dr. Medbery!
It makes sense to choose a facility that can respond to the patient's needs. But, it begs the question...why wouldn't the facilities with the most experience in Gamma Knife (ie, UVM and UPM) add CyberKnife to their treatment arsenal? In my mind, it would certainly lend tremendous credibility to the procedure. Perhaps that's a question I need to ask them..?
Abby
Dr. MedberryPittsburgh has a CyberKnife, but restrict its use to non-intracranial sites. I can't tell you for sure, but I suspect that they have contractual issues with the Gamma Knife that have them doing that. In addition, they have a great deal of experience with the GK and want to stick with it. As I mentioned, a lot of centers have access to both. But the longer you have invested in a particular technology, the less likely you are to want to invest in a newer technology that in their minds is duplicative. We like having the option of fractionating treatment when we feel it is necessary, but some places are taking the stance that fractionated is not PROVEN to result in better outcomes. I think we generally respect our respective positions. I had some e-mail interchanges with UPMC about joining in a protocol comparing single fraction GK treatment with fractionated CK treatment for acoustic neuromas, but they felt they needed to decline to join such an effort, citing unwillingness of patients to be treated randomly. If single fraction treatment is selected, then the only advantage of the CK in most cases is the lack of necessity of placing the frame. THere are raare cases where the GK caqnnot treat tumors that are in extreme positions, but that is not likely to be true for skull-base tumors.
Clinton A. Medbery, III, M.D.
St. Anthony Hospital Cyberknife Center
