Gamma Knife info from a friend in London

[ppearl214]

This email, I share with you all now, may be full knowledge to some, but maybe not to others in the decision making process.  A dear friend of mine in London shared this with me when I was asking her about radiosurgery.... thus, her initial reply.  So, I wanted to share this with you all and welcome any and all comments that agree or disagree with what she notes. BTW, she's an anesthesiologist (gawd, I hope I spelled that right) in a major London hospital.

Phyllis

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Morning Phyl,

Wow, so decision time is imminent.

The gamma knife was just starting to be used when I did my neuro job, so I don't know a huge amount about it except radiosurgery is seen by many as the way ahead for neurosurgery because it is minimally invasive (i.e. no surgical incision). It allows for surgery on tumours that would be considered inoperable if traditional open surgery was carried out or for lesions located near delicate structures. The mortality and morbidity rates are much lower and the hospital stay is shorter too. It costs less than open surgery too. It is also far less painful - the worst bit is usually having the stereotactic frame fitted!

In this country the Gamma Knife is used for more Acoustic neuromas than any other type of tumour. It is ideal for tumours less than 2.5 cm and is better for retaining useful hearing. A large(ish) series of 500 patients has been studied at Pittsburgh and control of the tumour exceeds 90%. Obviously, there isn't yet real long-term follow-up but of 162 of the Pittsburgh patients (followed for a minimum of 5 years), the rate of tumour control was 98%, normal facial nerve function and trigeminal nerve function being preserved in 79% and 73% respectively. These sort of results have also been supported by work done in Stockholm.

However, there are, inevitably, some potential post-radiosurgery problems:

The tumour might not actually shrink in sixe for several years and in some cases might actually swell post-radiation. The swelling is thought to be a good sign though as it predicts tumour "implosion"! There is thought to be a risk of carcinogenesis though and there may be malignant change in the neuroma which one has to accept would not have happened if the tumour had been excised surgically.

You should be given all this info (and more) and the chance to ask questions when you are referred for radiosurgery.

It would be lovely to see you if you do make it over later in the year.

Take care,

Kate

[meb]

Is there a female approx 40years who has had FSR at Mass General.  Trying to get feedback on process and outcome.  I had 1.5-1.8cm AN and because of age fall in middle category for surgery or radiation Tks for info

[jamie]

It all looks pretty much on point, except for the following statement:

There is thought to be a risk of carcinogenesis though and there may be malignant change in the neuroma which one has to accept would not have happened if the tumour had been excised surgically.

There have been spontaneous malignant transformations (although very few) in intracranial schwannomas following radiation and surgery, so I disagree one would have to accept that it wouldn't have happened after surgery. Intracranial schwannomas are very very rarely malignant, and the school of thought amongst those who do not have bias is that it usually has nothing to do with the form of treatment chosen. Extracranial (outside the skull) schwannomas, particularly in folks with NF transform malignantly more often, with or without treatment. Here's a quote from Pittsburgh:

Malignant schwannomas are rare, but have been reported de novo, after prior resection (34), and after irradiation. We answer that this is always a risk after irradiation, but that the risk should be very low. We have not seen this yet in any of our 5,400 patients during our first 15 years experience with radiosurgery, but quote the patients a risk between 1:1000 and 1: 20,000. We reported one patient with a malignant mesenchymal tumor of the cerebellopontine angle that resembled an acoustic tumor (36). One report from Japan found a malignant tumor four years after resection, and six months following radiosurgery. The time interval after irradiation was too short to be causative (34).
http://www.acousticneuroma.neurosurgery.pitt.edu/or.html

[russ]

Hi
  Re The email; Talk about splitting hairs! In reality, the carcerginious rate for spontaneous, isolated unilaterals which are irradiated is not worth the mention.
  The rate of conversion to malignanacy ( I have read places ) for NF-2 mediated ANs which are irradiated increases to 6%.
  But then; Considering some do indeed develop malignancy following irradiation OR surgery, they apparently are 'destined' to do so with or w/o Tx of ANY kind, even if 'watch and wait??
  My personal feeling is, all considered, we need to stop worrying about malignant ANs and think of the other 'potential' dangers of w/w or Tx.
  Re Stats, I still don't believe it's proven one treatment type has long term advantage over another or more favorable outcome with the exception of Middle Fossa for intracanicular ANs and, more negatively, irradiation of ANs larger than 3.0 cm.
  Take care all!
  Russ

[antoinette]

Hi Phillis, I am wondering if anyone has gathered some info about the success of GK on surgically operated AN, not debulked but with a chance that some cells had remained. I also would like to know if debulking ANs does avoid facial problems. The auditory nerve is pretty well useless but even the slightest action there is very important and if debulking is easy on facial nerves, could it be easy just the same and make it possible not to cut the auditory nerve as well. What if the AN has "tendrils" going in the cerebellopontis angle.
It seems that past ANA had mentions of many debulking with GK treatment to finish the job.
ant
Could we, short of stats, produce a grouping (patients who did it and how satisfied they are) regarding this particular way to use GK?
I know 2 myself who are very satisfied, there was no bad outcomes in spite of the tumor sizes, and they were back on their feet in a very short time.

[ppearl214]

great post/questions antoinette... I could pose it to my "connection" in London or locally..... would be curious myself.  Let me see what I can find out.

Phyllis

[bob_michigan]

apparently are 'destined' to do so with or w/o Tx of ANY kind ................ 'potential' dangers of w/w or Tx.

I'm knew and don't immediately know where to learn this:   
w/o = without,  but what is   w/w  and Tx

...  like to know if debulking ANs does avoid facial problems. ... slightest action there is very important and if debulking is easy on facial nerves, could it be easy just the same ...  past ANA had mentions of many debulking with GK treatment to finish the job.

and what is debunking?

Thanks very much,   Bob_Michigan

[becknell]

Tx = treatment. I thikn w/w refers to with or without
Debulking refers to a procedure where part of the tumor is removed, but not all of it. Then the patient can follow up with radiation to stop the remainder of the tumor from growing. The idea is that this allows greater preservation of the facial nerve that complete tumor removal would. Hope this answers your questions, Bob.

[gloriak]

isn't w/w 'wait and watch'?