srs vs gamma knife, unsure

Posted By
1/7/2014 8:57am
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Replies: 16


It's been a while since I've posted but I've got a question or two.

After winning a fight wiht my insurance company about coverage I was denied access to a PD-1 trial in December because the researchers realized during prescreening that I had not tried the BRAF inhibitors yet. Not that it would have mattered- I would have been denied anyway because after successfully treating 7+ mets in my brain last summer with WBR there were 4 new ones found at prescreening- just about a month after a clean scan. Following denial of enterance to the trial I was placed on the BRAF/MEK combo and have been on those drugs for about a month, give or take.

I had a follow up MRI on Friday and my results appointment yesterday locally. Unfortunately the images from my December MRI did not upload into their system so we were not able to make an acurate comparison (and the written report does not give measurements), but based on what I saw on this new scan I very much expect I will be referred back to a center for either SRS or gamma knife. Hopefully they can get the computer guys on it and be able to more acurately compare the scans later this week, but in the mean time...

I know a little about the basic differences between the two methods of targeted radiation, but I guess I'm soliciting opinions about which may be the better choice and other's experiences with this therapy particularly regarding side effects. 



POW - (1/7/2014 - 9:59am)

I'm sorry for your disappointment about getting in to the PD-1 trial last month. What a bummer! But I hope the BRAF/MEK works for you and kills the new brain mets.

 As far as I know, the term "stereotactic radiosurgery (SRS)" is a generic term that applies to all highly focused multi-beam radation treatments. Two companies make the machines that do this and they use trade names. One machine is called a "Gamma Knife" and the other is called a "Cyber Knife" but they are both types of SRS.

Are you asking about the difference between Gamma Knife and Cyber Knife?

Thank you. I had no idea SRS was a generic term. I don't know about the requester of this post but stereotactic radiation is something the drs suggested for me if i have too much pain to make it through ipi. Good news is I'm going to make it through fine. Already on 3rd ipi dose.

POW - (1/7/2014 - 12:49pm)

Yes, we usually hear about SRS being used to treat brain tumors. However, in recent years the manufacturers have developed machines that are able to focus multiple radiation beams to various parts of the body, not just the brain. I don't know much about those treatments, however. I do have to wonder how they make your spine or liver hold completely still during the treatment. For the brain, they have to use that metal halo thing or make a customized plastic mask for each patient. I'll have to look into that some day.

Janner - (1/7/2014 - 1:07pm)

My father had a targeted "4D" radiation for lung cancer.  They basically did a treatment plan to map location during all aspects of his "breathing".  At the 3 subsequent treatment visits, they put him in a balloon body vise that immobilized him.  They actually predicted what his lung movements would be and the tumor radiation was targeted WITH his breathing and tumor movement taking place.  This was for stage I lung cancer and several years later, he is still NED for that cancer.  I was pretty amazed that they were able to do this high dose radiation in real time, and my Dad was thrilled.  3 treatments versus 30 daily treatments for someone in their 80s was a huge advantage.

POW - (1/7/2014 - 1:46pm)

Thanks, Janner. That's amazing! "4D", eh? I guess that refers to time being the 4th dimension. Maybe I'm just getting old, but it sure seems that technology is advancing at breakneck speed! So glad this technique worked so well for your father.


ecc26 - (1/7/2014 - 12:56pm)

Yes, thank you for correcting me. I knew that there were 2 different machines, and I know the basic procedure and results are the same/similar, but I was wondering if there was any thinking out there that one might be better than the other for any reason. 

as for the combo working in the brain- yes, I'm aware that that can happen, but it doesn't always happen and really these inhibitor drugs don't get rid of tumors anywhere, right? They shrink things down and people can have "clear" scans, but there's still cells hiding out in there so when I get to the point where the drugs stop working these brain mets are likely to come roaring back, even if I do get a response in my brain (which is uncertain at the moment).

I'm thinking that even if the comparison scan shows stability it's worth it to go ahead and treat these 3 and hopefully get rid of them for good. Don't know if it was the radiation or the Ipi this summer that killed the other brain/meningeal disease, but my brain responded well so I'm banking on the same thing happening with radiation on these. 


POW - (1/7/2014 - 12:58pm)

Are you saying that you have/had leptomeningeal melanoma?

ecc26 - (1/7/2014 - 1:05pm)

Yes, well, likely. 

Last June the MRI showed 7 tiny brain mets and "several areas suspicious for leptomeningeal disease". That's the reason I had to do WBR instead of SRS this summer. They wanted to make sure any potential leptomeningeal disease was treated, which requires WBR. All of my MRI's since then (Aug, Sept, Oct, Dec, Jan) have shown no evidence of leptomeningeal disease and all 7 of the June mets are gone. What I have now is 3 (or maybe 4, needs a closer look to be sure, Dec report had 4) completely new mets in completely new locations.

Mat - (1/7/2014 - 1:04pm)

Not sure of the answer, but I would still proceed with G-knife even if there is evidence of shrinkage.  The hope with shrinkage is that the combo is working on the brain and will help prevent additional brain mets.  I think you are correct to point out that targeted therapy should be viewed as more of a bridge--hopefully a long bridge.

ecc26 - (1/7/2014 - 9:54pm)

I agree with you about proceeding even if thre is a reduction in size. My doctor had said we could delay if there was reduction in size, but I'd rather get them treated now than wait until these drugs stop working and things get complicated again. Given the response from this summer's WBR, I have every reason to believe I would get a good response from SRS.


Mat - (1/7/2014 - 12:40pm)

Eva, as you point out, it would be good to get a comparison with the prior MRI as the GSK combo can shrink brain mets (shrunk one of mine prior to G-Knife).  They can also compare versus the MRI done on the day of the G-Knife procedure.  G-Knife is a very easy procedure (I have no experience with having it done after WBR, however).  I had it done on a Friday and was back to work on the following Monday.  Plan for possible minor headache and tiredness for 24 hours or so following the procedure.

ecc26 - (1/7/2014 - 12:59pm)

Thank you, that was helpful. Did you have the halo screwed to your head or the mask?

Mat - (1/7/2014 - 1:06pm)

Screws and I was under a mild anesthetic.  The screws leave scabs that fall off after 2 or 3 weeks.

Brendan - (1/8/2014 - 10:34am)

I've had them both.  Gamma is delivered in a single setting so you will receive all the radiation at once (imagine one big punch).  With cyber knife, the radiation is delivered over several sessions (I had five).  Your tumor will get punched more, but each punch is weaker.  The total amount of radiation is the same (I think-or at least close).  the day after my gamma knife I had a seizure, but I had no problems with the cyber knife.

I think you should ask docs about the possibility of a seizure (met placement might play a role).  The facility is close to me, so going five days for the cyber (as opposed to one for the gamma) was not a problem.

good luck.

Janet Lee - (1/12/2014 - 11:21am)

After reading all these posts about gamma-knife vs. cyber-knife, I'm more confused than ever.

My husband has had cyber-knife on two separate occasions for different brain mets. For both treatments, there was only one session.

He also had "SRS" at another facility, but they didn't call it ether gamma- or cyber-. The melanoma neuroradiation oncologist did it in two sessions because one of the mets was a little larger and she wanted to treat it with more radiation, but in smaller doses, twice.

I have also been told by the head of radiation oncology at another medical facility that cyber-knife is the oldest technology and the newer technology is better.

Janet Lee

kylez - (1/12/2014 - 1:40pm)

Hi Janet,

I'm pretty sure there are other SRS systems besides Gamma Knife and Cyber Knife for cerebral melanoma. I have been treated with both Cyber Knife and Gamma Knife. I believe Varian makes at least one SRS system, Trilogy, used for melanoma. Proton therapy is, I believe, another type of SRS used for melanoma, though I cannot swear to it. E.g., see There may be other some other SRS systems I've missed.

From the manufacture's documentation, the resolution of CyberKnife is about 5mm. The resolution of Gamma Knife is about 3mm. Not sure about Trilogy or Proton Therapy.

Hope this helps. 

- Kyle

2 primaries; lung/brain mets in past; paratracheal lymph node currently; participating in  Opdivo/Lirilumab trial