Repeat radio surgery

[Lizard]

Hi y'all,
Its been a while since I've visited, for those who remember me I had horrible headaches post surgery and saw Dr. Ducic in DC.  I'm still headache free and just had my first child 7 weeks ago!  I never would have been able to be a Mom if if wasn't for the help and support I received on this forum, you are all amazing! 

On a separate note, my father had an AVM (arteriovenus malformation) or bleed in his brain in the late 80s he went to Univ. Pitt med center for (at the time) cutting edge gamma knife.  The vein was dead and they weren't worried about it bleeding again, but low and behold 20+ years later it bled again.  This time not as severe, but still will need to be treated.  The reason I'm asking here is that he has received multiple opinions, the cutters want to cut and the radiation guys want to shoot it.  The bleed is in the same area as last time and they told him surgery was very risky because it was deep in the brain near the "speech center".  I don't really know why they would recommend surgery and after my ordeal it scares the bejesus out of him!

What shook my dad the most was that the "cutter" neuro told him it was dangerous to do the radiation again.  Cyber knife or other fractionated radiation was recommended due to its lower dose, but I wanted to see if any of my AN buddies had multiple treatments for recurring tumors?  What was the result and did the Dr's tell you a similar story?

Thanks so much as always your help is much appreciated!
Liz

[PaulW]

Yes it is possible to reradiate.

I believe repeating radiosurgery for an AVM is very different from repeat radiosurgery for AN's
So for the AN'ers out there do not think that this is in anyway the same.
AN's are tumours, and AVM's are really not. The radiation dosage to treat AVM's is therefor MUCH higher, the repeat dose is apparently higher still. Volumes of AVM's tend to be quite large too, all of this makes radiosurgery for AVM's more challenging.

Interesting to see Dr Kondziolka appear as one of the names in the research.
Well worth consulting multiple experts in this field for their opinion.

Found these papers
http://www.ncbi.nlm.nih.gov/pubmed/21743357
http://www.ncbi.nlm.nih.gov/pubmed/22077445
http://www.ncbi.nlm.nih.gov/pubmed/20568667

[PaulW]

With regards to the CK versus GK debate. Both machines can be the best, depending on the tumour size, location and shape.
I am very happy with my choice of CK for my AN, however if I was confronted with repeat radiosurgery for an AVM my choice would probably be GK.
GK creates radiation hotspots which is potentially problematic for AN's but is potentially beneficial for AVM's

As you are repeating radiation, complications from exceeding your lifetime dosage to the surrounding brain tissue and causing serious complications become a risk.

This forum isn't used much anymore, but it maybe worth giving it a try and seeing if you get a response from some of the best radiosurgeons going around. 


http://patientforum.therss.org/

[mesafinn]

Hi Paul,

I'm trying to decipher what you mean by "GK creates radiation hotspots."  I thought I knew what a radiation hotspot was, but the way you word it here confuses me a bit.  Can you clarify?  Thanks.

P.

[PaulW]

GK applies radiation in spheres, or isocentres as they call them.
You are positioned in the machine, shutters are open, and 196 or 201 beams of radiation depending on the model of machine will zap your tumour and a little sphere is treated.  The shutters are then closed, the machine moves you a little bit and the shutters are opened again, and another sphere is zapped. The process is continued until the entire tumour is covered.
Trying to zap a 3d shape with spheres has its problems. As you can imagine to cover the whole tumour means these little spheres need to overlap, its the overlap that creates the hot spots. GK will typically deliver double the dose of radiation at the middle and to the hot spots than what is received at the edge of the tumour.
For an AVM receiving a higher dose in the middle is probably good, as it has a better chance of obliterating the unusual blood vessels.
And that's all an AVM is, is a bunch of unusual blood vessels.

GK is an isocentric treatment...which means it treats in spheres.

CK is typically applies non isocentric radiation. beams are shot from all different locations and angles.
There is no central point of focus for the beams
A computer calculates where these beams will come from, and a good analogy is that the cyberknife robot paints the tumour with radiation rather than treating with spheres.

Cyberknife will typically give 25% more radiation to the middle of the tumour than the edge, while Gamma Knife will typically give 100% more radiation than what is received at the edge of the tumour. Neither of these things is necessarily good or bad, but depending on your situation there could be an advantage with one or the other.

For an AVM exposing the growth to 100% more radiation is potentially good.

For an AN, exposing a nerve to 100% more radiation, if the nerve runs straight through a hot spot, its potentially bad for the nerve.
Lucky the nerves normally sit to one side of the tumour and this may explain why CK and GK results are so similar with AN's

As this is a repeat treatment they will need to take into consideration the last treatment, as the effect of radiation are cumulative, and they will not want to exceed the amount of radiation a healthy piece of brain can stand.

[mesafinn]

Very helpful and much appreciated!

I continue to learn from you.

Thanks!

P.

[nftwoed]

Hi;
   I see there are many more knowledgeable re, radiation here, but, just from what I've read from others through the years: Repeat radiation can be done if GK. I've never heard of repeated FSR/CK due to the overall higher, end result dosage in gys.
   AVM has been known to be difficult to treat in some whether surgically, or with radiation. For some, the pain remains chronic.

[latirus]

I had the 'other' procedure (Gamma Knife) and was told that it could not be radiated again.  And that if I required surgery it might be complicated by the scar tissue.  So choosing GN radiation was a one-shot gamble.

[PaulW]

Radiosurgery in general can be repeated, but it is highly dependant on the previous treatment as to whether it can be done again or not.
The larger the tumour volume, the higher the dose, the involvement of critical structures, the more fractions you have, and the less precise the machine, the less likely you are to be able to repeat radiosurgery.
So repeating radiosurgery is very much dependant on your personal situation.

A 3cm AN heavily impacting the brainstem with a volume of 12.5cm3 needs a lot of radiation to kill it...
Think 12.5 lb of frozen turkey in your microwave and how long it would take to defrost.

Compare that to a 10mm x 5mm x 5mm AN with a volume of 0.13cm3
How long will it take to defrost one 0.13lb chicken nugget in your microwave?
Radiosurgery and defrosting turkeys, or nuggets in some ways is very similar.

Small tumours in the Internal Auditory Canal are often 4-5mm away from touching the brain.
This gives the radiosurgeon a buffer and the ability to keep doses to the brain very low.

While a 3cm tumour, its touching the brain all over the place, there is no buffer, and to ensure total tumour coverage, and to allow for inaccuracies they will often zap a small margin of the brain with the full dose to ensure a cure.

The magic of radiosurgery means that this large amount of brain involvement will hopefully not be a problem. But if you re radiate it again it could be.

I hope that helps explain why everybody is different. 

As for Fractionated versus single fraction.
Whats the chances of getting Salmonella if you defrost your turkey over 24 hours sitting on the kitchen bench, refreezing it and doing it again.

Whats the chance of Salmonella if you defrost 1 nugget in 1 minute, and refreeze it again and defrost it the same fashion the next day..

Repeating radiosurgery is very dependant on whether you have a nugget in your head or a turkey, or if you choose to defrost on the kitchen bench, or use the fast defrost option on your microwave.