CyberKnife Rocks!

[6pick]

Back from my 6 month.

Headaches I'm experiencing are normal, pain behind the ear is normal and best news of all: black spot in tumor. Necrosis is good! 

Mark

[ppearl214]

Mark,

Aye-men!  Take it from someone that is now 5-yrs post-CK and can attest to what you are feeling.  Continued wellness wishes to you!

Congrats!
Phyl

[PaulW]

I am now 9 months post Cyberknife, and feel great.
I feel normal again.
Hearing improved and is now well within normal range.
So no hearing deficit to complain about.
Tinnitus is gone.
Balance not perfect, but no wonky head any more.
Just mild stumbling in the dark over kids bicycles and skateboards.

[6pick]

I am now 9 months post Cyberknife, and feel great.
I feel normal again.
Hearing improved and is now well within normal range.
So no hearing deficit to complain about.
Tinnitus is gone.
Balance not perfect, but no wonky head any more.
Just mild stumbling in the dark over kids bicycles and skateboards.

Thanks, Phyl, glad to be here.

Paul,
Really?
Your hearing is within normal range?
That's terrific! Mine's pretty much gone. Then again, my tumor was bigger (believe me, I'm not bragging) and I think I've had it since before 2001. I thought hearing improvement was not generally possible. Comment?

Mark

[Jim Scott]

Mark ~

Congratulations!  5 years ago I didn't know what 'necrosis' meant.  Today, I'm cheering you for having it. 

Jim

[leapyrtwins]

Necrosis is AWESOME!!! 

Congrats!   

Jan

[PaulW]

Yes I have been very fortunate with my hearing.
Its still early days and I am fully aware that hearing often deteriorates after radiosurgery.
My hearing is currently sitting at PTA of -20db with my bad ear and
Speech Discrimination is 100%.
Just Prior to treatment I had a PTA of -30db and SD 80%
So my hearing has actually improved quite a bit.
Listening to music, being in large social gatherings is pleasurable again!
It is unusual for hearing to improve after radiosurgery but it does happen.
While I have no proof I put this down to receiving treatment early within 8 weeks of noticing hearing loss.

There has been a lot written about accuracy of different machines.
From what I can gather, and I am not a doctor, the accuracy of the machine, the "Conformity Index" and the "Dose Drop Off Rate"
are all very important to the eventual outcome.
Even more confusing is the fact that depending on the size and shape of the tumour, different machines could be better than others in different situations.
From what I have read the important things seem to be, for hearing preservation, to keep the amount of radiation below 4Gy to the Cochlear
And if the Hearing Nerve gets less than 16Gy to any part of the nerve. It will probably be fine too.

This is where the conformity index and dose drop off make the real difference.
With Cyberknife I received 13Gy to the 80% isodose line.
Therefor the maximum received by tumour was 13 / .8 = 16.25 Gy
Even if the machine was off a bit and hit the nerve with the full dose there is a reasonable chance the nerve would survive.

If Gammaknife was used you would be treated with 13 Gy to the 50% isodose line.
The centre of the tumour would receive 26Gy, if the nerve happenned to pass right through the middle of the tumour its probably a gonner.
Fortunately the nerves normally get pushed to the outer edge.
So thats the conformity index, and Cyberknife is very good at this, especially with small tumours.

Then there is the drop off rate.
I believe with my treatment plan I had the 20% isodose line 3mm away from the tumour.
So essentially, and anything less than 4Gy is considered to do no harm.
So 3mm away from the tumor I receive 13 Gy x 20% = 2.6Gy
My Cochlear and Brainstem were more than 3mm away... So damage to both would be considered as nil.

Again I am not a doctor, but hey there is considerable information available on what happens to good tissue when zapped with a particular dose of radiation.
Sparing good tissue is the secret to successful radiosurgery and I believe a fast drop off rate and low conformity index, are crucial to sparing good tissue.
Especially for AN's as the nerves, cochlear, and brainstem are all implicated

I cannot speak more highly of the treatment and the result to date.

[6pick]

Thanks, Paul. I'd like to say I understood all that but I'd be lying. It does give me ammunition for questions and study, however.
My PTA was about 72, pretty much the same as 6-months ago.
Speech Discrimination in the affected ear: 0.00%. I could usually make out two syllables, sometimes one would end in "s" - I think.

But "Conformity Index", "isodose line", "Dose Drop Off Rate" escape me (although dose "Dose Drop Off Rate" implies to me a measure of how each CK emission stops: whether it stops abruptly or "peters out"). Please explain

By "accuracy of different machines" you mean the individual CK machines? I guess it stands to reason that no two are identical.

I have no idea how many Gys went to the Cochlear and how many to the hearing nerve - this is what I need to ask the doctors.

Ultimately though, my hearing is what it is and I consider myself so incredibly lucky that I have the hearing ability that I do.



Jan, Jim, thanks so much for cheering me on. You two are the best!

Mark

[PaulW]

Conformity index is essentially how uniform the radiation is applied to the tumour.
In an ideal world this would be 1, where the entire tumour gets just enough radiation to kill it, and the radiation is spread uniformly throughout the tumor.
In practice this is not currently possible which means there are some parts of the tumour that will get more radiation than is actually required to kill it.
If a nerve happens to pass through the middle of that hotspot within the tumour , it may destroy the nerve.
So the more uniform the radiation is to the tumour the better the chance of something like a hearing nerve surviving if it happens to be in the midde of the tumour.

If you were treated with 13Gy at the 80% isodose line.
That means the outer edge of the tumour received 13Gy
The maximum dose to the middle of the tumour would have been 13/0.8 or 16.2Gy

Drop off rate is the rate at which the radiation dose reduces away from the tumour.
The faster the radiation drops away the better.

Big Tumours, Small Tumours, Irregular Shaped Tumors.
Brand A maybe better for Large irregular shaped tumours, nerves in the middle.
Brand B maybe better for Large Spherical Tumours with no nerves in the middle
Brand C maybe better for small oblong tumours, with nerves through the middle of it

The accuracy difference between the machines probably matters less than the dose dropoff rate and the conformity index.

There are so many variables.
Treatment planning is very important to get the best out of every machine.

I am not a doctor.
But I have spent 10 years fixing robots, and very complex, computer and electromechanical systems.
 
My personal view and it is just that.
Is that Cyberknife has a technical edge in small AN's where hearing and nerve preservation is important.
This has yet to be proved conclusively from medical papers, but I think it is heading that way.
and again please this is my personal view only.
Do Your Own Research

[6pick]

Thanks, Paul, that was very clear and helpful.

Markl