Gamma Risk

[Echo]

I know there have been many posts over the years regarding the risk of a malignant growth after Gamma, but what is the current most widely accepted view? I am pretreatment and giving this a lot of consideration.

I have listened to an interview with Dr. Stephen Chang from 2010 where he stated he believed the risk for a malignant growth to be "1 in 10,000 possibly even 1 in 20,000".  I listened to the webinar with Dr. Kondziolka who I believe referenced "1 in 1,000 as a statistic, but he believes it could be closer to 1 in 5,000".   I spoke to neurosurgeon who said "1 in 1,000" and I received a letter from an Otolaryngologist that said "While extremely rare there would be the remote possibility one could induce a malignancy in a radiated tumour.  This typically happens years if not decades afterwards.  Malignancies such as sarcomas or glioblastoma multiformens have been reported prior." 

I find all the info to be rather confusing and wonder if anyone really does know.  Can any of the long term folks on this site tell me if over the years they have heard of any members developing a malignancy as a direct consequence of having Gamma or Cyber Knife treatment?

With thanks,
Cathie.

[Jim Scott]

Hi, Cathie ~

Obviously, the statistics for malignant growths resulting from Gamma Knife radiation treatment are relatively rare but cannot be stated with absolute accuracy.  For most AN patients considering radiation treatment, it suffices that the odds of experiencing a malignancy subsequent to GK treatment is very remote and not a serious cause for concern, even if it has to be considered. 

To answer your query regarding knowledge of any of our ANA discussion forum members experiencing a post-GK malignancy, I can state - as a member for 7 years (and a moderator, so I read all new posts) - that I have never seen that occur.  If it has, the member did not report it, which I believe would be highly unlikely.

Bottom line: post-radiation malignancy can occur but the chances are very rare and while real, should not be a primary factor in your treatment decision.

Jim

[arizonajack]

My uneducated guess is that your chances of being hit by lightning, a meteorite, or winning the lottery are better than your chances of developing a malignancy after radiation treatment.

 

[Echo]

Gentlemen, I  like both your responses.  It's one of those things I'm having difficulty wrapping my head around and you've both given me some much needed perspective.

Thanks,
Cathie.

[mesafinn]

Hi Cathie,

I certainly understand your question as this was one of the biggest things I processed, too.  I didn't want a decision I made today to impact me 10 years from now when all we're trying to do is the right thing.

When I spoke with Dr. K by phone, he said that he quotes the 1 in 1,000 stat but that it was more likely 1 in 10,000.  Then he paused and said, "Theoretically it's possible but practically, it's exceptionally rare.  We quote those stats but it doesn't really happen."   When I asked Dr. Lunsford at Univ of Pittsburgh, who has done 12,000 GK procedures and 1600 ANs, he has had one malignancy.  But he said that individual had a history of brain tumors and they could not conclude if the malignancy was a result of the GK or a natural occurrence based on that person's histology.

One note I found out after my GK but wish I had been told beforehand came from Dr. Rutka (Toronto).  It was the first time I had read this but he wrote, "Pertinent complications of radiation treatment include a 5% chance of facial weakness (not paralysis).  There would be a 5% chance you might experience significant headaches post radiation.  This is the result of protein shedding from the tumor that blocks brain fluid absorptive pathways...There is a 5% chance you may experience significant facial numbness/pain.  This is the result of radiation injury to the nearby trigeminal (facial sensation) nerve."

"Following radiation you would also be at risk for developing other tumors intracranially.  The development of post-radiation meningiomas is well known and is reported in the world literature."  I had focused on malignancy potential, but I did not know much about the potential for meningiomas (another type of benign tumor).  I question his reference that this is "well known" and "reported in the world literature" because as I explored the "world literature" fairly extensively and never came across this.  But wanted to mention it because I believe in information.  I'm not convinced his statement is accurate.

As Arizonajack mentions, I concluded I had greater risk on the 401/QEW (Ontario reference!) and I would be fine.  So will you!!

Peace,

Patrick

[mk]

"Following radiation you would also be at risk for developing other tumors intracranially.  The development of post-radiation meningiomas is well known and is reported in the world literature."  I had focused on malignancy potential, but I did not know much about the potential for meningiomas (another type of benign tumor).  I question his reference that this is "well known" and "reported in the world literature" because as I explored the "world literature" fairly extensively and never came across this.  But wanted to mention it because I believe in information.  I'm not convinced his statement is accurate.

It is easy to drive yourself crazy with all this information. Dr. Rutka mentioned about the development of meningiomas after radiation. Well, what kind of radiation? Whole brain radiation for example is much different than the controlled dose provided by stereotactic radiation (SRS). I think I have indeed read in the literature about the risk of developing meningiomas after whole brain radiation, so in one sense the quote is correct, but not applicable to the present case.

I also know that the doctors at the GK centre in Toronto have reported, and published a  couple of cases of appearance of a glioma multiform, following SRS (I think Linac and GK). They use some criterion to attribute it to the previous SRS treatment (based on overlap with the region that had been previously radiated). But there is always a question on whether these tumors would have appeared spontaneously anyway. After all, there are many people who get malignant brain tumors, without a history of previous radiation.

My impression is, that if there was indeed some association, we would have seen at least a few cases by now. As Jim mentioned, in all these years, and multiple searches on archives etc., other venues such as the old Cyberknife forum, etc.,  I have never seen a reported case.

Marianna

[Echo]

Thanks Patrick and Marianna - more good points to consider.

It's easy to get lost in all this data and overwhelmed with processing it.  Thanks everyone for helping me sort through the details.  And yes, driving on the 401/QEW Ontario HWY is probably a much greater risk to my life than Gamma or Surgery!

Cathie.

[PaulW]

As discussed the risk is very low.

Even when a malignancy is detected, was it the radiation that caused it?

Was the person with the malignancy predisposed to malignancy?

Its known that some people are more susceptible to radiation than others.

Could it be that for 99.9% of the population radiosurgery is very safe, but for 0.1% there is a 1:10 chance of malignancy?

Also the risk of malignancy probably varies with the volume of the tumour and type of tumour, the bigger the tumour that is treated the more radiation that is required and the risk also increases. So the risk of treating a small tumour could be 100 times less than treating a 3cm tumour.

Even if the tumour does become malignant, it does not mean death. There are some documented removals, where growth was detected, the tumour was removed successfully with the cancerous component was locked away inside the growth.

[mk]

Even if the tumour does become malignant, it does not mean death. There are some documented removals, where growth was detected, the tumour was removed successfully with the cancerous component was locked away inside the growth.

My understanding is that the transformation of a benign AN to a malignant one is extremely rare (only a few documented ones, out of which it is difficult to say whether the tumor was malignant to begin with, since a biopsy would be needed for this-which is only possible when the tumor is removed surgically).
Of more concern is the appearance of secondary tumors, such as gliomas etc.

Marianna

[SV2011]

Hi I had a consultation about this before radiation, I think this malignancy percentage occurs mostly in NF2 patients. Of course with everything there is a risk, I think the statistical percentages of complications after surgery might be higher than the risk of the tumour becoming malignant. Personally, I don't look at statistics anymore, they don't really go in my favour. At the moment I am 16 months after stereostatic radiation treatment and my tumour is still inflammed so I am already in the minority! It is a very hard choice to make, what swung it for me was that there was a high probability that the whole tumour wouldn't be removed, and what was left behind would have received radiation if it started to grow so I figured I would just try radiation and deal with the consequences.

[PaulW]

Swelling 16 months after radiation is very common indeed.
Don't feel disheartened.
Tumours can swell for 2 years, that's not unusual
The 2 and 3 year MRI are probably the most important.
Most successful treatments will see shrinkage in the 2-3 year stage.
I am not a doctor that's my personal understanding.

I believe the faster dying AN's are also the ones with a faster cell turnover, which probably means that your tumour was faster growing too. Its known that faster growing AN's are less likely to respond to radiation.
So have some comfort in the fact that not much has happened.

 

[arizonajack]

Swelling 16 months after radiation is very common indeed.
Don't feel disheartened.
Tumours can swell for 2 years, that's not unusual
The 2 and 3 year MRI are probably the most important.
Most successful treatments will see shrinkage in the 2-3 year stage.
I am not a doctor that's my personal understanding.

The following image from the internet supports that understanding. It's a 36 month post radiation progression.

http://ars.els-cdn.com/content/image/1-s2.0-S0360301612004336-gr3.jpg