Gamma Knife or Cyber Knife - how do you choose?

[mcrue]

What are the top "pros and cons" of each?

[arizonajack]

The following article should answer that question:

http://emedicine.medscape.com/article/857604-overview#showall

[mcrue]

So it's Gamma Knife if I read that article correct?

Plus, the following insert was alarming:

"while complications of radiation were significantly reduced: rates of facial nerve dysfunction and trigeminal neuralgia at a mean follow-up period of 5 years were 1.1% and 2.6%, respectively."

[PaulW]

Nearly all the permanant facial and trigeminal problems occurred with larger tumours. Some patients insist on getting gk even with tumors larger than 4cm these size. Over 3cm you are at much higher risk of a complication.

[arizonajack]

So it's Gamma Knife if I read that article correct?

Only you can make that decision.

Plus, the following insert was alarming:

"while complications of radiation were significantly reduced: rates of facial nerve dysfunction and trigeminal neuralgia at a mean follow-up period of 5 years were 1.1% and 2.6%, respectively."

Didn't alarm me. I chose GK.

Here are some more articles:

http://thejns.org/doi/pdf/10.3171/2012.7.GKS12783

http://www.rportermd.com/gammacyber-knife.html

Dr Porter was my neurosurgeon.

[Echo]

When my An was diagnosed at 1.8cm I was told with surgery I was looking at a 10-15% risk of facial nerve damage with surgery.  When it grew to 2.4% my risk of facial paralysis grew to 25% while Gamma Knife offered only a 1-2% risk.   Those statistics along with the other risks I faced with surgery, made Gamma Knife the better option for me.

Cathie

[PaulW]

GK Pros
slightly more accurate.
Less radiation to surrounding tissue around tumour due to faster dose fall off, theoretically less complications.
Better shielding protecting rest of body to superfluous radiation. Reducing cancer risk
Minimum beam size 4mm

GK cons.
Head frame
Not usual to fractionate, which may have an advantage in AN's but questionable.
Higher maximum radiation dose to centre of tumour creating a radiation hotspot which may be detrimental to nerves if located in the middle of the tumour.
Head frame distorts and can cause inaccuracies.
Location of tumour is not confirmed during treatment opening up the possibility for geographic misses. Misses have been confirmed as a large cause of radiation failures
More difficult to block radiation to critical structures


CK pros
No head frame more comfortable
Can be fractionated... But it's value in Acoustic Neuromas is questionable.
Tumour position is validated during treatment reducing the chance of a geographic miss from setup errors.
No hotspots reducing risk of nerve damage in a hotspot if this is a risk.
CK supports beam forming on the M6 model which is useful for larger tumours, and concave tumours
Flexibility of the robot allows more freedom to avoid critical structures

CK cons
Minimum beam size 5mm
More radiation to whole body due to less shielding very slight increase cancer risk
Slightly less accurate.. About 0.2mm for small Acoustic Neuromas (this is not considered significant as there are other errors from imaging as well)
Dose fall off is not as fast as GK especially for larger tumours.

Something people may not be aware of is the Penumbra effect.
These radiation beams are not quite the piercing straight sharp edged beam we may imagine.
The penumbra I believe is around 3mm on both CK or GK so arguing over which is more accurate maybe purely academic

I think both machines are great machines.. A good team is needed too.
The choice in my book between these two is head frame or no head frame and the team of medicos


There is also the GK model c versus the GK  perfexion
There are better results for treating AN's with the perfexion

[mcrue]

Higher maximum radiation dose to centre of tumour creating a radiation hotspot which may be detrimental to nerves if located in the middle of the tumour.
Head frame distorts and can cause inaccuracies.
Location of tumour is not confirmed during treatment opening up the possibility for geographic misses. Misses have been confirmed as a large cause of radiation failures
More difficult to block radiation to critical structures
 

Something people may not be aware of is the Penumbra effect.
These radiation beams are not quite the piercing straight sharp edged beam we may imagine.
The penumbra I believe is around 3mm on both CK or GK so arguing over which is more accurate maybe purely academic

I think both machines are great machines.. A good team is needed too.
The choice in my book between these two is head frame or no head frame and the team of medicos


There is also the GK model c versus the GK  perfexion
There are better results for treating AN's with the perfexion

Can an experienced team mitigate factors such as:

a) head frame distortion causing inaccuracies
b) geographic misses causing radiation failure (because tumor moves during radiation??)
c) blocking radiation to critical nerves structures (GK can't protect the facial nerve like CK treatment can??)


What is the GK success rate for small tumors less than 2cm?
98% success?


Also, have there been any "horror stories" regarding radiation treatment for AN's similar to those related to microsurgery? As I understand it, the worst "side- effect" from radiation treatment is if the tumor regrows.

[rupert]

Paulw does a lot more research than I but, I've never heard of head frames being distorted and that would be a new one for me.  Frankly I can't imagine the force needed to bend it. They are titanium and not fragile.  I suppose there is human error involved in anything as far as geographic misses. Never heard of that either as the AN is imaged right before treatment.  I would like to see statistics on those events.  I assume they would be extremely rare.  GK is very precise.  I was told by my team that they target around the nerves.  I couldn't say if that's all nerves,  or just major ones.  I specifically asked Dr. K. about this and he showed me the nerves from the MRI on a big monitor,  where they were  and that they target around them.  As a side to that, facial problems are also extremely rare with GK.
CK, as noted is more radiation over several sessions.  The main difference between the two are the machines of course. GK is limited to the head area whereas CK can be used for different areas of the body.  It is a very good option for treating prostate cancer. Both machines have their niche but, I give GK the nod as a bit more precise.
Said many times here, whatever treatment you go with choose experience. Better results occur with more experienced teams.  I was extremely blessed to have Kondziolka, Lundsford, Flickenger and others on my GK dream team.

[PaulW]

Can an experienced team mitigate factors such as:

None of these things can be totally mitigated but can be worked with. Its not black and white.
All of these things can be mitigated by providing more radiation to good tissue.
For instance if they zap an extra millimeter all they way around the tumour it would allow for the inaccuracies of the machine.   

So its a balancing act. More Margin = More radiation= more side effects, but better tumour control.
Less Margin = less radiation, less side effects but higher risk of failure

An experienced team will totally understand the challenges and take the appropriate actions

a) head frame distortion causing inaccuracies.
Using phantoms and alignment procedures the GK Team will understand the level of inaccuracies and adjust the machine appropriately.

b) geographic misses causing radiation failure (because tumor moves during radiation??) Not for small tumours, they don't move as they are locked in the IAC

c) blocking radiation to critical nerves structures (GK can't protect the facial nerve like CK treatment can??)
Gamma Knife typically treats to the 50% Isodose line, while CK treats to 80% Isodose line.
This is configurable for both machines, but due to how they work the isodose lines differ and each is appropriate for each machine.
Disadvantage of the 50% isodose line is a higher maximum radiation dose typically 26Gy versus 16.25Gy for CK.
Mostly the nerves are to one side of the tumour, so may not matter.

The results between GK and CK are pretty much identical, Fractionated and non fractionated.
We can argue about the technical pluses and minuses but at the end of the day, it probably comes down to head frame versus no head frame, and very small increase in cancer risk to the rest of the body from CK. Any other advantages of either machine have failed to show up statistically.

[mcrue]

Thanks,

I agree that an experienced team equates to a higher success rate.

Dr. Lunsford at UMPC in Pittsburgh is an excellent choice for Gamma Knife, as well as Dr. Kondziolka at NYU in New York.

Dr. Chang at Stanford is an excellent choice for Cyber Knife.

They both feature experienced teams, and they perform numerous procedures annually on AN's. 

There are also some excellent local teams throughout the country as well.

My "Top 10" fears from radiation treatment are probably most common:

1. Tumor regrowth
2. Hearing Loss
3. Facial paralysis
4. Mis-calculaton - zapping wrong part of brain or brain necrosis!
5. Tinnitus issues
6. Eye problems
7. Balance problems
8. Headaches - longterm
9. Trigeminal nerve problems
10. Cancer

11. Making me slow or "off"
12. Fatigue - longterm
13. Cognitive issues
14. Hemifacial spasms
15. Hydrocephalus

16. Should I expect a "new normal" after treatment?


Which one of my fears is most likely to manifest?

[mcrue]

How often do they perform "routine maintenance" and "recalibrate" the machine to make sure every beam is going to where it should go?

What happens if there is a power failure in the middle of the treatment?

Does Dr. Lunsford have the latest upgraded machine available or is "older" technology?

[Blw]

I just had GK after leaning towards CK. I changed my mind because there is suspicion that my tumor involved the facial nerve, although it is still not known for certain. The reason I changed is that GK has been around much longer and has an extensive track record of success, which can be found by reading reviews of large clinical studies in the literature. In fact, I was surprised by comparison, how few studies have been published for CK. In my case, I viewed it as I needed radiation to absolutely work, because facial nerve surgery is catastrophic. If I knew for sure that there was no facial nerve involvement, I would have leaned toward CK.

[PaulW]

Radiation is most effective on small tumours. Just remember that the total amount of radiation that you need is related to the volume of the tumour. The bigger the tumour the more radiation you will need and the higher risk of complications.
At 10x5x5mm my tumour was all in the IAC and did not even touch the side of my brain. There was a 3mm gap. The volume of my tumour was 0.125cm3.  A 3cm tumour has a volume of 10.6cm3
That's 85 times bigger than my tumour by volume and will need 85 times more radiation to treat it.
 I was very comfortable getting radiation for my baby tumour.
As your tumour is growing aggressively it's pretty obvious that w&w is no longer a suitable management strategy. Which leaves the other two options surgery or radiation. The potential side effects of radiation won't get any better with a bigger tumour. If you are considering radiation I would seriously consider it sooner rather than later, because if your tumour keeps growing at the rate it has you will lose that option in just over 12 months. Choose an experienced team and they will do all that needs to be done. The neurosurgeons and radiation oncologists that operate these machines are geniuses.  Dr Chang, Lundsford, Kondziolka are the geniuses genius.. These guys are way smarter than you and I will ever be, and some times you just need to trust them. I think right now you need to weigh up surgery versus radiation. Forget which machine, and choose the team you are most comfortable with.

[PaulW]

We have all heard about the 3cm limit for radiation which is about 10.5cm3
Check out this paper... Got zapped with Cyberknife for a tumour the size of a quart of milk and only had a mild reaction.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4689568/

Makes my tumour which is nearly 1000 times smaller by volume look pretty pathetic