Large dose of radiation??? anyone???

[tenai98]

Given that I have already lost my hearing and balance nerve due to the translab surgery, the doctor wants to give me one large dose of grays via cyberknife.  Has anyone had one large dose???  My facial nerve is entwined in the tumor and I'm thining that one large dose may affect the facial nerve?  Has anyone had just one large dose?  I know many of you have had several treatments. 
JO

[Tumbleweed]

JO, I remember one or two people on this forum have had 1-dose CK, but the overwhelming majority get three or more doses. As you know, fractionating (dividing) the doses is thought to better preserve cranial-nerve function. Perhaps your doctor has a good reason to give you one big dose. In any case, you should get a second opinion if you haven't already.

Dr. Steven D. Chang (renowned Stanford-based CK practitioner and neurosurgeon) will review your MRI and give you his recommendation for free. His email address is sdchang@stanford.edu.

Best wishes,
TW

[PaulW]

Gamma knife always delivers radiation in a single dose. Some say that single dose is better than multiple doses as some tumour cells will be "born" part way through the treatment and will never receive enough radiation to kill those new cells.

There are guidelines for radiosurgeons to work under for acoustic neuromas which means most radiosurgeons prescribe a maximum dose of 13 Gray. At that dosage facial nerve injuries are close to zero.

I had single dose Cyberknife, My balance, hearing and facial nerve are all good.
I think you will find that statistics on facial nerve preservation are exactly the same for single dose or multiple dose radiosurgery.

http://www.irsa.org/AN%20Guideline.pdf
 

[Sheryl]

Hi Jo - my husband has a different type of tumor called a meningioma.  He had one surgery in 2004 and when it regrew he refused the recommended second surgery and opted for one dose of CK.  He did well with it for two years but the tumor once gain regrew and he had no choice but a second craniotomy in 2009.  The tumor then reappeared for a third time and he has just finished 30 sessions of IMRT radiation hoping for stability.  We had been concerned about too much radiation but the radiation oncologists agreed that his brain could take more.  At this point, I think he has hit his radiation limit plus more surgery is not recommended because of increased deficits so we have to hope that stability sets in.  They do not feel that shrinkage will occur but the tumors (there were 3 found) are extremely small.

Good luck - keep us posted,
Sheryl

[nftwoed]

Jo;

  What is a "single large dose" to that Dr? Linear accelerators weren't really designed to do that. They will deliver a large dose in fractions, however.
  You do have the facial nerve to consider, and I'd want another opinion mbefore jumping at the one large dose idea if the choice were mine.
  IRSA puts out some good info, but one must remember why they exist and who are members. Yes, I dislike many car sales personel also.

[rjbarker]

Hi,
Dosage these days is usually not lower than 12-13 Gy with either Linac/CK or Gamma Knife.  CK, a Linac, can deliver in one dose. How high a dose does he have in mind??  This is the important item you leave out.
Back in 1991 before they began to lower the dosage I had 17 Gy in one dose with Gamma Knife. No problem for the facial nerve. No balance problems. The dose did knock out what was left of my hearing in the one ear.
d*** B

[tenai98]

The dose is 13 grays

[rjbarker]

Hi again,
As we all seem to agree, 13 Gy is pretty standard these days for single dose treatment. It's not considered "high," except perhaps by those who feel the dosage might be even lower to help preserve hearing and yet still control the tumor.
d*** B

[mk]

Jo,

it seems to me that basically your doctor advises to do a single shot of radiation (similar to GK, which typically uses 12-13 Gy), rather than fractionated (which is typical to CK, which if I remember well usually uses 3 doses, about 8Gy each, someone please correct me if I am wrong). This makes me wonder though, what would be the advantage of doing CK, instead of GK? (except of course of proximity, since Ottawa only has CK).
In any case, I don't really think that there is a difference, and this dose is considered safe for the facial nerve.

Marianna

[Tumbleweed]

fractionated (which is typical to CK, which if I remember well usually uses 3 doses, about 8Gy each, someone please correct me if I am wrong). This makes me wonder though, what would be the advantage of doing CK, instead of GK?

Marianna

I received three doses of 6 Gy each when I received CK for my then medium-size tumor. The biological equivalent was 11.5 Gy. (You don't simply add the three doses to arrive at the biological equivalent of a single dose.)

One advantage of CK is that the fractionated doses gives the cranial nerves that are also irradiated time to heal in between treatments. There is evidence to suggest the nerves recover faster from the irradiation than the tumor does. So the tumor dies, but the cranial nerves hopefully survive to a greater extent than if they had received one large dose of 11.5 to 13 Gy.

It's important to realize that none of these radiation technologies attempt to avoid irradiating cranial nerves that are in the way when irradiating the tumor. This relates to another advantage of CK: it delivers a far more homogeneous dose of radiation throughout the tumor than GK. With CK, the dose applied at the center of the tumor is only 15% greater than at the tumor's periphery. With GK, the dose is fully double at the tumor's center compared to that at the periphery. The arbitrary double dose at the tumor's center (also where the cranial nerve is often located) is thought to be the reason why the hearing nerve doesn't do quite as well with GK as with CK. Since the radiation's dosage must be large enough at the periphery to kill the tumor, GK's double-the-lethal dose at the center becomes an unfortunate necessity borne out of the technology. With CK, in theory at least, you get less collateral nerve damage due to the much smaller increase of radiation exposure at the center of the radiation cloud and where cranial nerves are unfortunately exposed.

Best wishes to all,
TW

[mk]

Thank you TW for clarifying this. Based on what you are saying therefore, even single dose CK would be more advantageous than GK, due to the more homogeneous delivery.

Marianna

[Tumbleweed]

I believe that's correct, Marianna. But GK proponents might argue there are other benefits to GK over CK that outweigh the drawbacks I stated. They're both excellent treatment choices.

Best wishes,
TW

[nftwoed]

Hi;

  I believe there was a study a few years back which gave CK a 5% advantage in hearing retention.
  To me, this is like comparing apples to oranges when one thinks of CK vs GK. There is a minor disadvantage to CK spraying the head with radiation to help align the equipment after the initial CT Scan. I'm unsure if it's enough radiation to matter.
   I think John Hopkins, who were heavily into theory of FSR in the 90s ( Williams, et al ) have resorted to GK again.

[PaulW]

I believe the radiation caused by the 3D xray positioning in CK is about the same as a head CT scan 

[Tumbleweed]

  I believe there was a study a few years back which gave CK a 5% advantage in hearing retention.

FWIW, I've seen more than one study that gave CK about a 10% advantage in hearing retention: 70%, vs 60% for GK.

Best wishes to all,
TW