Continued hearing loss years after radiation

[jbbrown15]

I'm 6.5 years out from fractionated stereotactic radiation on my 2.9 cm AN.  I recently looked at my audiograms over the course of years.  I only had mild loss pre-treatment, but have had big declines in hearing since then.  Audiograms at 6 months, 2.5 years and 5.5 years each show additional hearing loss.

I'm' curious about whether anyone else has noticed changes in hearing years after radiation.  Why would it continue to decline so long after radiation treatment? 

I also had a major flare of vestibular symptoms around 5 years after radiation and have not yet recovered to where I was before that flare. 

I wonder if the loss of hearing function could be evidence that my vestibular nerve was still suffering new damage 5 years out?

Jean

[Echo]

Hi Jean,

I had Gamma Knife for a 2.4cm AN, 3.5 years ago.  I was told at the time that it could take up to 5 years to see the full effect of the treatment.  I was to expect complete hearing loss within 3 years.  Well my hearing has deteriorated but it's still somewhat usable. I can hear loud sounds but my word discrimination fluctuates from 30 - 20% and that has been the pattern for the past 3 years.   So to answer your question, yes, I do think it's possible to still see some deterioration in your hearing this far out from treatment. We all react somewhat differently but if you have concerns, I would check with your Doctor.

Cathie

[ANSydney]

Being told to expect complete hearing loss within 3 years following Gamma Knife isn't a good endorsement of GK. I thought one of its selling points of GK was increased chance of hearing preservation (above 50% speech discrimination).

[PaulW]

There is increasing evidence that hearing loss after radiation has multiple factors.
Here is a paper showing hearing loss caused by facial schwannomas that are not even in the Internal Auditory Canal

https://www.ncbi.nlm.nih.gov/pubmed/27701738

The latest theory is that proteins given off by the Schwannoma are toxic to the inner ear.

This explains why Gamma Knife for other tumors doesn't cause hearing loss.
Why Facial schwannomas do cause hearing loss
Why getting Gamma Knife sooner has better hearing preservation rates.
Why being on Watch and Wait can cause you to become deaf in the absence of growth..

Gamma Knife does not kill the tumor it just stops it from replicating, so in theory it keeps pumping out bad proteins for years..

https://www.ncbi.nlm.nih.gov/pubmed/26307578

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3302957/


 

[ANSydney]

I'm querying the statements:

Why getting Gamma Knife sooner has better hearing preservation rates.
Why being on Watch and Wait can cause you to become deaf in the absence of growth..

From this paper  ( https://pdfs.semanticscholar.org/2cef/abe8e8eef1ae32cab8bcf3c71dd75f53387c.pdf ), Gamma Knife accelerates hearing loss and watch and wait gives the best outcomes for with regards to hearing. Notably:

"In the literature, to our knowledge, there have been no reports of the hearing preservation after 10 years or more after hearing preservation surgery or radiotherapy. In the present study [no active treatment], 95 patients had been observed for 10 years or more. According to the AAO classification, 46% maintained good hearing after 10 years or more compared with 45% using the WRS classification and 75% of patients with 100% speech discrimination at diagnosis.".

[PaulW]

Ahhh you have to love these studies....

With Acoustic Neuromas you can find studies supporting W&W, surgery or radiation!

https://www.ncbi.nlm.nih.gov/pubmed/19057423

https://www.ncbi.nlm.nih.gov/pubmed/21121792

https://www.ncbi.nlm.nih.gov/pubmed/22937934

[ANSydney]

Paul, yes you can get a study that shows evidence of just about anything! That makes in hard for us ANers!

Those three papers are all from a single hospital in Marseille France and by the same authors. So its the one source.

I went through my papers last night and you can certainly get any answer you would like about gamma knife and hearing. There are papers that show that gamma knife is protective for hearing loss and some that show there is no difference or accelerates hearing loss:

https://www.ncbi.nlm.nih.gov/pubmed/25771841

https://www.ncbi.nlm.nih.gov/pubmed/25850598

I'll quote a passage from the second paper:

Active treatment with microsurgery or gamma knife surgery did not appear to be protective, because patients who were observed had the greatest probability of durable hearing. Patients in the surgical series had the greatest hearing loss.

Two more papers of interest are:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4831944/pdf/nmc-56-186.pdf

http://thejns.org/doi/pdf/10.3171/2016.7.GKS161494

The first paper (Fig. 2) shows a linear drop in hearing preservation out to 4 years and stabilizing thereafter at ~55% hearing preservation. The second paper (Fig. 3) shows a steady decline forever. At 10 years only 24% preserve hearing and at 15 years only 12%. It just keeps getting worse. Unabated.

My conclusion is that if you have a vestibular schwannoma, you will probably loose you hearing no matter what path you take. There are just ways to speed up the process.

Getting back to the three cited papers from Marseille, they had a failure for conservative management of 74% and growth for 77% of tumors. The "conventional" wisdom is that two-thirds don't grow (I believe it is closer to three-quarters don't grow - and of course I can provide papers as evidence!). Nobody is talking about only one-quarter of vestibular schwannoma tumors don't grow! Also, 74% failure rate has to be compared to https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1502035/pdf/sbs16095.pdf . Here only 7.6% failed conservative management. Are the first set of papers over treating or the second paper undertreating. I can imagine overtreatment, but how do you undertreat with no negative outcome. For this reason I put less weight on the Marseille set of papers.

From my extensive research, there are reasons for gamma knife (a large AND rapid growing tumor), but if all you are after is hearing preservation, gamma knife just makes things worse (and you have to content with the possibility of communicating hydrocephalus, malignant transformation and new deficits). There may be a case for a rapid growing tumor that is not large, but here you are gambling.

It takes a very good understanding of where errors, biases and conflicts can occur in articles to know what is going on. Having a vestibular schwannoma is a serious event, but understanding the literature is a bigger problem. Hercule Poirot have a field day.

My final comment is that there is no interest in solving the problem. Step one in arriving at the correct picture would be to establish the natural growth of the tumor. If I were to run an experiment in three different locations around the world with 100 patients each I would get the same answer for natural growth. From this base we would be able to solve the mystery that is a vestibular schwannoma. In all these decades we still do not have an answer to the fundamental question, what percentage of ANs grow?

[PaulW]

One of the problems with the study above is that many people that have radiation have it later in age.
One study I read if am correct showed that your hearing declined at the same rate after 5 years as it would naturally, and that Gamma Knife did take about 20db off your hearing.
Using the 50:50 rule as this stud has. 50 percent word descrimination score, -50db hearing loss as what is considered servicable hearing there is almost no room to play with.

By the time you are 60 even a normal person will be down to -15-20db add radiation -20db plus age related hearing decline for 10 years -15db. Add 10-15db loss for the original tumour hearing loss that took you to the doctor and your hearing won't be considered serviceable after 15 years

Further to that, with the improvement in hearing aids they now consider -65db as serviceable.
So many people in that study that show they do not have serviceable hearing actually do

Also many people that don't have serviceable hearing still have hearing.
Which means you can still locate the direction of sounds. Any extra information coming in the bad ear does get interpreted by the brain, which does help with hearing overall. Some hearing is better than none at all

Radiation often affects the high frequencies but doesn't affect low frequencies anywhere near as much. My hearing today at 500Hz and below is perfect, 7 years after radiation. My high frequencies are not great. That is not unusual for someone who has had radiation. That can make your PTA look bad, but your perception of hearing loss may not be as diminished because you still have very good hearing at lower frequencies.

There are so many variables.

One of the problems with W&W studies is often the people that are lost to follow up, have gone elsewhere for treatment. This can skew the results..
I guess just like proactive gamma knife could show high success rates, purely because 50% were not going to grow anyway.

http://www.redjournal.org/article/S0360-3016(16)00040-7/abstract

There are certainly some studies out there indicating that getting a small AN radiated at a younger age has very high levels of hearing preservation. However many of those could be radiated unnecessarily today. There is some research being done looking for bio markers in the blood to help determine whether your AN is a grower or not. Maybe one day in the near future we will treat those that need treating earlier, and those that don't can remain on W&W.

[ANSydney]

Whether radiotherapy preserves or accelerates hearing loss certainly has differing opinion.

I would be interesting in getting a link to the normal hearing loss with age figures. It's hard for me to find, but in my notes (I don't know the source), I've got 6 dB/10 year loss with age. Also -15 dB normal loss for a 60 year old appears to be high.

With regards to those lost to follow up in studies, I think they have statistical mechanisms for accounting for those that are lost to follow-up.

The paper you have cited has flaws as discussed in https://www.anausa.org/smf/index.php?topic=23294.msg979773067#msg979773067

My personal assessment is that radiotherapy accelerates hearing loss. You do not have radiotherapy to preserve hearing. There is a place for radiosurgery and that is for a rapidly growing tumor that is threatening to become large. If there is not rapid growth (>5 mm/year) that is not threatening into get large, a 2 year period (5 MRIs) will give you information about growth. Remember, most tumors do not grow following diagnosis and its very rare for tumors to grow after 4 years from diagnosis.

[PaulW]

My personal view is that radiation improves the odds of hearing preservation for some, and makes it worse for others. Problem is we don't really who it will help and who it won't.
Radiation for other tumours doesn't cause the same amount of hearing loss if any hearing loss.

It appears to me that the causes of hearing loss are complex.
While there are links to nerve damage, compression, and reduced blood flow to the cochlear it doesn't explain everything.
I personally think the protein emissions from the tumour, which are proving to be ototoxic play a far bigger role than we give them credit for.
How those emissions work for W&W versus radiation is not understood at all.

[ANSydney]

It is interesting that radiation for other types of tumors, presumably in the same area, do not cause hearing loss. It would be great to discover the cause of hearing loss and then radiation may be able to be adjusted to improve outcomes. Lots to be discovered yet.

[PaulW]

I guess that's why this paper is so important
https://www.ncbi.nlm.nih.gov/pubmed/27701738

Its yet another paper showing a link to protein emissions damaging your hearing.

A facial nerve schwannoma with no IAC involvement shouldn't affect your hearing, but it does..
Once again the cochlear is damaged.

More links to proteins and hearing loss

https://www.ncbi.nlm.nih.gov/pubmed/22377650

https://www.ncbi.nlm.nih.gov/pubmed/26690506

https://www.ncbi.nlm.nih.gov/pubmed/23512073

It is known that radiation makes the tumour produce more proteins for a lengthy period until it reduces or stabilises after radiation.

I feel a significant factor of hearing loss is the amount of ototoxic proteins that are in the cochlear, your age, and how long you have been exposed to the proteins.
It explains a lot of stuff... like why some people with big tumours have no hearing loss.(fast growing tumour but cochlear not exposed to toxins long enough)
Why small non growing tumours cause hearing loss with no visible nerve damage. (Exposed to toxins for 10+ years)
Why radiation for AN's causes hearing loss but doesn't for other tumours to the same extent. (Radiation causes AN's to emit more proteins for a few years)
Why facial schwannomas cause hearing loss, but other tumours often don't in the same location.
Facial schwannomas have the same genetic make up and emit the same ototoxic proteins as AN's

[JLR]

Hi All, My hearing was near perfect before and after Cyberknife. Had CK in 2010. By 2016 the AN started to grow. November 2016 I had retrosig surgery. At that time I lost my hearing surgically on the right side.  I am 67 years young and up till surgery my hearing was perfect even with the radiosurgery. I had regular hearing tests - although I had and still have tinnitus - all those audio tests were good.  Although my left side compensates for the right sided deafness but in a noisy crowd i.e wedding, the noise is overwhelmingly loud. Joan

[ANSydney]

Hi Paul,

Thanks so much for links to those papers. I've only read the abstracts, and they are interesting. And one of those is from July 2017!

The one that really caught my attention is the last link. It appears that some tumors secreted proteins that are ototoxic (damage hearing), while others are otoprotective. That is a new revelation for me. "This study highlights FGF2, a mitogen [a chemical substance that encourages a cell to commence cell division] known to protect the auditory nerve, as a potential tumor-secreted mediator of hearing protection in VS."

It's good to have a researcher on the forums.

Yesterday I was reading a paper to increase my knowledge about nerves that pass through the internal auditory canal ( https://www.ncbi.nlm.nih.gov/pubmed/15255963 ). Interesting aspect, of no practical use, is that the cochlear nerve has about 25,000 individual nerve fibres each with their own insulation generated from our favorite cell, the schwann cell. That's 25,000 separate channels of information conveyed from the cochlear to the brainstem.

I'm beginning to examine the hypothesis that hearing loss may be dependent on which nerve the tumor is growing on. For instance, I have a large tumor with little hearing loss, but altered taste. So little hearing deficit, but more than average facial nerve deficit (taste). If the tumor is growing on the superior vestibular nerve, it would be in contact with the facial nerve, but not the cochlear nerve. Perhaps this explains my situation. Conversely, if the tumor is on the inferior vestibular nerve, which most are, it would be contact with the cochlear nerve therefore more hearing loss (through mass effect or ototoxicity).

Let's hope the medical community start coming up with some consistent knowledge (and techniques) on how to help us.

[PaulW]

ANSydney... next time I am in Sydney or you are in Adelaide we should catch up for lunch and compare notes... Must be something in the water here in Australia to do lots of research..
Or is it just the complete vacuum of decent information available in Australia that drives us to do this.

Check out this paper here

https://www.ncbi.nlm.nih.gov/pubmed/25434946

As discussed there are so many factors that could cause hearing loss..
My gut feel is that there could be a subset of patients that could benefit from radiosurgery for hearing preservation. Unfortunately we really don't have studies, with more granular detail to make a judgement. Mind you that could be the very same subset that perform well in W&W too.