Hi, everyone:
I have some interesting info to report following my CyberKnife (CK) treatments last week at Stanford. Much of what I'll cover here entails answers to questions many of us had posed in numerous other posts and which I promised I would try to find out during my time at Stanford. To track down each thread would be too time-consuming, so I'll report on everything in one thread here.
First, Steve was right about my CK dose. I erroneously thought my treatment plan was to receive 11.5 Gy in each of three treatments. In reality, I received 6 Gy three times, for a total biologically equivalent dose of 11.5 Gy (this figure is less than 6 + 6 + 6 Gy, as fractionation reduces the total dose in biological terms to be less than the total one would arrive at simply by adding the three doses together).
Dr. Chang told me before treatment setup that the 6 Gy for each treatment would be delivered by between 80 and 140 beams, resulting in healthy tissue along each beam's path receiving roughly 1% (1 divided by roughly 100 beams) of the total radiation or about 0.06 Gy. (Steve was correct that the calculation is just a matter of simple division: total Gy divided by number of beams). When I asked Dr. Chang how this compares to the dose of radiation one is exposed to from, say, a single X-ray, he said you can't really compare CK and X-ray because an X-ray exposes a relatively large area of the body to radiation whereas CK exposes the body to pencil-diameter beams about 6 to 7 mm in diameter.
Dr. Gibbs told me that, with CK treatment, no effort is made to avoid irradiating cranial nerves that the tumor is wrapped around. Since my entire IAC (internal auditory canal) was virtually filled up with the expanding tumor, that meant all the nerves in the IAC would receive the full dose of radiation that the tumor would receive. This points again to one of the benefits of CK over GammaKnife (GK): homeogeneity of radiation dose. Whereas GK delivers roughly double the dose of radiation (100% more) at the tumor's center compared to at the periphery, CK delivers only about 15% higher dose at tumor center than compared to at the periphery. If I remember correctly, the vestibular nerve is the one most centered in the IAC (with the facial nerve at the top of the IAC and the hearing nerve running along the bottom). What I glean from this is that the vestibular nerve probably receives less radiation with CK than with GK, although I didn't think this through enough at the time of my meeting with Dr. Gibbs to ask her if my reasoning is correct.
I told a nurse practitioner who works with Dr. Gibbs (my radiation oncologist) that I would like to take anti-inflammatory herbs and supplements during and after treatment to discourage tumor swelling, if it was safe to do so. Her response was, "That's good." That is, not only was this acceptable, but she thought it was a good idea to do so. As for taking anti-angiogenic supplements during and after treatment, she thought it was okay to do so but didn't indicate that she thought it would be helpful.
Each of my treatments lasted 32 minutes. I asked for and was given 1 mg of Ativan, a fast-acting anti-anxiety medication, before each treatment, to calm my nerves and keep me from fidgeting while receiving the radiation. (Although CK compensates for the patient's movements during treatment -- to keep the radiation focused on the tumor -- it is still important to stay as still as possible.) During my first treatment, I barely, if at all, felt the Ativan and was a bit anxious throughout the treatment. When I came in for the second treatment, the steroids I was given the day before (as a prophylactic treatment to preclude tumor swelling from the first treatment) were making me really hyper and therefore even more anxious. I was a bit panicky during portions of that second treatment. So for the third and final treatment, I took some valerian root extract (an herbal sedative) about one hour before treatment. I also arrived 30 minutes before treatment and asked for an increased dose of Ativan to calm my nerves, hoping it would kick in earlier and before treatment began. After determining that I would not be driving afterwards (my wife would be instead), Dr. Borcher (the meds doctor) gave me 2 mg of Ativan (a double dose). I sailed through the third treatment, calm as a cucumber. Those of you who will undergo CK in the future: don't be afraid to ask for a higher dose of medication if you are anxious. The doctor will accommodate your request; there is no need to suffer through panicky feelings while being treated. Also, although Ativan is supposed to work within minutes, I found taking it 30 minutes prior to treatment worked much better for me. Indeed, for my second treatment, for which I received the Ativan only 10 or 15 minutes prior to commencement of treatment, I didn't feel the drug's effect until
after the treatment was over. I suspect my adrenaline largely countered its effect, but my point is
arrive early for treatment, don't be afraid to request the dose you need, and take the meds early to give them a head start before treatment begins.
Eileen, my CK technician, gave me a few updates as to our progress during treatment, so I could anticipate how soon we would be finished. Unfortunately, during my first treatment, I had them play music so loudly that I couldn't understand anything she was saying. When she said, "We're about 1/4 of the way through, and you're doing great," all I heard was "blah blah blah blah, blah blah blah blah." For all I knew, she was telling me the building was burning down and we had to evacuate, or that there was a major malfunction with the CK machine and I had only five more minutes to live.
My advice: have them play music softly so you can hear what they're saying over the intercom. And choose soothing music; uptempo party music did nothing to calm my nerves!
If I think of anything else useful to report, I'll add to this thread. My brain is a little foggy right now, so this is all I can think of at the moment.
Best wishes,
Tumbleweed
