Radiation accuracy?

[allegro17]

Hi everyone,

I have been doing research on different types of SRS and keep seeing the following come up:

GK uses 201 source cobalt unit designed exclusively for non-invasive brain surgery, with radiologic accuracy better than 0.3mm, while CK is a single source linear accelerator, and not exclusively for intracranial SRS, with 1 mm accuracy and dose outside the target area is 2x-6x greater than with GK

To add to all pf this, I am now dicovering that the Novalis BrainLab may be different in more ways from Gamma knife than I orignally had thought - I was led to believe it is essentially the same process but produces the radiation differently, but now it seems that there may be a great degree in how accurate it is compared to Gamma Knife?

Does anyone have any more or better info for me regarding what I have already come up with?  I thought I had made such progress when I decided I wanted to go with radiation but now feel severely confused about which type of radiation treatment to pursue!

Thanks,

Laura

[ppearl214]

hey Laura,

I've seen you posing these questions to the docs on the CK Support site as well and tickled you are doing all of your research.

I tried to help by doing a seach option here... as there as been a LOT discussed here over the past couple of years regarding this very issue (where is Mark when I need him.......).

so, I'm going to suggest this....

Go to the "radiation/Radiosurgery" forum page (where all the threads for radio is posted). At the top, do a "Search" option for "radio accuracy".  the Search results will provide many discussions regarding this very subject.  Much data has been posted and I'm not versed enough to summarize it here, but the Search results should give you all you need.

again, to the Radiation/Radiosurgery Forum home page here... that way, the Search option will only look for results in this sub-forum.

Hope that helps.
Phyl

[Tisha]

Laura,

I asked Dr. Chang the difference between the Novalis and the cyberknife (I knew I was going to do one or the other-FSR).  He said that there really wasn't much of a difference except cyberknife is more accurate (less than .7mm target error compared to novalis of 1.4mm).  I don't know anything about gamma, sorry.

[Mark]

Hi Laura,

I thought I would respond because Phyl summoned me from the outer reaches 

I saw the responses that Drs Medbery and Spunberg gave you which were certainly practical for your situation. Given that your hearing in the affected ear is virtually gone, there isn't a lot of value in a fractionated approach. CK and GK can both do a one dose treatments and the primary difference is the lack of an attached halo with GK, so it's mostly comfort.

The source of the radiation is irrelevant to the discussion. GK is cobalt and CK and the radiotherapy machines are LINAC. Both work the same on the tumor biologically, cobalt is just more of a disposal problem

The accuracy information you referenced is mostly GK propaganda. They are talking machine error, not total error. All machines have error related to the CT scan, GK also has an error factor related to the calibration of the Halo, then there is the level of the machine error. Long story short is that CK has been shown to have a total error of better than .9 mm in clinical studies. GK is closer to 1.2-4. Radiotherapy machines like Novalis tend to be lower accuracy which is one of the reasons their protocols are 25-30 days with low doses to avoid collateral damage.

The accuracy difference between CK and GK is minimal if you are doing a one dose treatment, more important if you are doing a fractionated protocol which only CK can do. Again, in your situation, with hearing not a factor, if you don't mind the halo being screwed in, then the GK would be fine.

Mark

[Tisha]

Mark,

For the one shot CK treatment, do all the beams converge together at one point like GK?  My understanding is that they do not for CK, rather it "paints" the tumor with no intersection.  Just trying to understand how a one shot CK works.  Thanks.  Tisha

[ppearl214]

Thank you, dear!

I thought I would respond because Phyl summoned me from the outer reaches 

[allegro17]

Thanks so much, your replies have been SO helpful

I am really stressed out today - talked to some Dr's in NY on the phone who do GK AND neurosurgery and it just seems that as a general rule nobody is really indicating radiation as a preferable option for me   So far I gather its becuase of my age/side effects and long term indications of radiation.  It is so hard to feel comfortable about it when Docs well qualified in both genres are advising against it   Man, I feel like I am back to square one.  I just feel so confused.

As far as CK vs. GK - now I wonder why, if CK is just as effective and possibly more accurate than GK, would anyone choose GK when there is an option that does not require the mask?  Would it make a difference for me if I do one chot CK or 3 doses?  I haven't heard of anyone who has done one dose so maybe it would be wiser to do what is practiced more commonly even if my hearing isn't an issue, but I wonder if for any reason single dose CK would be any better or different really than the 3-dose.

And on top of this a friend of mine who is interning in radiation oncology is even advising against radiation!  AND suggested I look into proton therapy or something if I wanted to go the radiation route because it is supposedly less toxic?  Arrrrgh.

Sorry if I am rambling, I feel really confused today.  It's been difficult to hear so many people advise against radiation in favor of surgery, even if it is a "personal" choice.

Thanks

[ppearl214]

Ok, let's try this.. first.. DEEP BREATH!  Ok, inhale... hold it... hold it... exhale! works like a charm!

I know of the reasons you note are mentioned from time to time... the key to radiation for an AN is the size and exact location. If it is (typically) over 3cm, you are generally ruled out for radiation.  If it is pressing against the brainstem in a big way (ie; brainstem is twisting, etc), then also, usually ruled out.

Now, I think of user "Sue".. Vancouver, WA... over 60 yrs old, had GK on her AN just after me... and she's doing fine.  THen, Jim Scott, surgical first, then radiation for the residual and definately over *coff* 25 yrs old! (Jim is also a Mod here, I have to be nice to him!)

Many choose GK as a one shot deal when the hearing has a high % of hearing loss.  Fractionated (ie; CK, Trilogy, etc) usually used to help preserve "serviceable" hearing. (In my case, my goal was to save my hearing, thus, I chose fractionated CK via one shot GK to help save my hearing, as well as other reasons).

said in respect to your friend, I believe they need to research CK and GK a little  more carefully re: the toxicity of radiation and these particular treatments.  Proton Therapy is a form of radiation. I know of many here that have had it done on their AN's . Problem is ... lack of data to prove efficacy on AN's as well as cost.. .VERY expensive to have done.. only a few proton centers in the States (Boston, LomaLinda and I believe Houston... someone pls correct me on that if I am wrong).  Now, scare tactics about radiation and cancer rates seems to be a common theme in discussions of radiation for AN treatments.  In your research, you have learned about the type of radiation that is used... the malignant factor is VERY low  and for me, I never even considered it a factor as I had as much chance of getting cancer crossing a  newly paved road vs. my CK treatment on my AN. 

You will know what your gut tells you... trust your research... trust your instinct, know what is best for your and your situation. If you need to take time to step back and catch your breath, then do so. This is not an emergent situation that you have to decide right away... you will know in your soul what is best for you.. and whatever you decide, we support you 200%.

Hang tough!
Phyl

[Mark]

Mark,

For the one shot CK treatment, do all the beams converge together at one point like GK?  My understanding is that they do not for CK, rather it "paints" the tumor with no intersection.  Just trying to understand how a one shot CK works.  Thanks.  Tisha

Hi Tisha,

I guess there is a fine line between "converging" and "paints" in my mind. Essentially, all radiosurgery works with a wide array of low dose beams from different angles delivering a consolidated lethal dose to only the tumor. GK does it with a combination of 208 ( I think) fixed beams while CK uses the robotic arm to position the beam in the optimum place for the computer generated treatment plan. I think the issue you're referring to is how homogeneous the dose is. If all the beams converge at the same point it would create what are known as "hot spots" and the other parts would be considered "cold" and may not have gotten a lethal dose. Given the tumor control rates, both GK and CK do a pretty good job of "painting the tumor" however CK's design give it a greater degree of freedom and it is generally regarded as being more effective in balancing the dose delivered.

For CK, the only difference between 1 treatment and three is the level of dose. I'm pretty sure that in the three day protocol the treatment plan / pattern is the same but the dose is 6GY for a total of 18 GY. If done in one dose CK would use an equivalent of around 12 GY which is the same as GK

Hope that helps

Mark

[Mark]

Thanks so much, your replies have been SO helpful

I am really stressed out today - talked to some Dr's in NY on the phone who do GK AND neurosurgery and it just seems that as a general rule nobody is really indicating radiation as a preferable option for me   So far I gather its becuase of my age/side effects and long term indications of radiation.  It is so hard to feel comfortable about it when Docs well qualified in both genres are advising against it   Man, I feel like I am back to square one.  I just feel so confused.

As far as CK vs. GK - now I wonder why, if CK is just as effective and possibly more accurate than GK, would anyone choose GK when there is an option that does not require the mask?  Would it make a difference for me if I do one chot CK or 3 doses?  I haven't heard of anyone who has done one dose so maybe it would be wiser to do what is practiced more commonly even if my hearing isn't an issue, but I wonder if for any reason single dose CK would be any better or different really than the 3-dose.

And on top of this a friend of mine who is interning in radiation oncology is even advising against radiation!  AND suggested I look into proton therapy or something if I wanted to go the radiation route because it is supposedly less toxic?  Arrrrgh.

Sorry if I am rambling, I feel really confused today.  It's been difficult to hear so many people advise against radiation in favor of surgery, even if it is a "personal" choice.

Thanks

I'd echo Phyl's sage advice and say "deep breath" as well  . It can all be very overwhelming

Some bullet point responses:

1) Can't speak for the docs you met with, but just because they have both treatment options available does not mean they are unbiased to one or the other. For example, House ear is clearly a surgery proponent to the extreme, yet they ( supposedly) have a GK although I've never heard of anyone treated with GK there unless they were physically unable to withstand surgery. I'd suggest continuing to visit with other docs who really specialize in radiosurgery. Chang at Stanford is excellent and you've already reached out to Medbery and Spunberg on the CK forum.

2) I think people probably pick GK for several reasons such as a) they like their doc and GK is all his / her hospital has b)they really didn't research machine differences c) they really don't mind the halo. Advantages of CK are primarily comfort and fractionation option. If given an equal option for both machines at the same hospital with the same doctors, very few would pick GK over CK I suspect ( and is certainly well proven at Stanford)

3) No disrespect to your friend, but I guess their comments would support why they are still an intern. If their issues are related to the malignant transformation issue, then Phyl already addressed that. For them to suggest Proton would be a better option is mind boggling to me. Phyl mentioned the high cost and limited studies, but what few have done have shown a higher level of treatment toxicity ( aka reduced results and complications) and no increase in efficacy outcomes. Several people on the forum have gone that route and seem to have good results to date, but I'm aware of others who haven't. I think your friend probably needs to keep studying 

Mark

[allegro17]

Ahhhhhhhh....ok.....

Thanks again.  Here's the thing.  Whenever someone suggests surgery, I start to freak out all over again.  But after to talking to you guys, I feel very similar to how I felt after speaking w/ Dr. Chang - more settled.

I remember after talking to him last week, I felt like suddenly I had the answer.  He made sense to me and in a factual, not biased kind of way.  When I got off the phone with him I felt like I had found my Doctor - I have to remember that!  So far he is one of two people who have made me feel completely comfortable about any given procedure and that holds a lot of water for me.  I keep coming back to that and really think that in the end this may matter to me as much as any of the facts or statistics.

Anyway,  Dr. Chang at Stanford just seems like such a great option on all fronts - so far I really can't see any reason I shouldn't go to him for CK for this.  I was ready to fly there right when I got off the phone with him

Thanks again!!!!!!!

[sgerrard]

Whenever someone suggests surgery, I start to freak out all over again.  But after to talking to you guys, I feel very similar to how I felt after speaking w/ Dr. Chang - more settled.

That is what we call the "gut feeling," and it is an important part of the decision process. You are the one who is going to have the treatment, and how you feel about it is very relevant. In the end I think it matters more than so many tenths of a millimeter of machine error versus total error, or whatever.

I had a similar feeling about Dr. Chang based on email. I somewhat tentatively sent my first email on a Friday evening, figuring I might hear from him in a week or so. On Saturday afternoon he emailed back, and by Sunday evening I had exchanged several emails, had all my questions answered, and like you, was ready to fly there.

So I did.

Steve

[mk]

I don't have much to add, everyone here has been providing great input. Just two points:

-About the choice of GK vs. CK, very often it is a question of availability and experience. GK has been around for much longer, there are tons of studies on it and many centres with experience. CK is newer, there are few centres with a lot of experience on it (Stanford and a few others), and it is not even available in some areas/countries. I believe that this is slowly changing, however it may take a few years. My point is that in many cases (like mine) there is no real choice. As you have seen on this forum most people had CK at Stanford, meaning that travel is involved and this is not always possible for everybody.

- Your friend might have been referring to "radiation", as in radiation used in cancer treatment. It is accepted by everybody that this kind of treatment is totally unsuitable for non-malignant tumors. GK and CK (and proton) are "stereotactic radiosurgery", which is completely different.

Marianna

[Tisha]

I had the same "gut" feeling with Dr. Chang.  I felt like I could trust him and his team (because Dr. Soltys probably did ALOT, maybe he even did it all...I should have asked).  Anyway, Dr. Chang is a nuerosurgeon and head of the CK team. He does 50/50 surgery/radiation.  I felt comfortable with his opinion.  I would also not be afraid at all to ask him any questions that you have, fax them to Scarlett...she'll get them to him and he'll call you.   

Personally, I'm still not comfortable with the comparison between GK and CK.   We know that GK has decades of statistics of tumor control behind it and you aren't concerned with hearing preservation.  I would want some explanation about the one shot CK.  Is if just effective as GK?   ARe there any published reports about that?  Ask him these questions, he doesn't care, and they are very valid.

Keep asking questions...they are good ones.  You'll know when you've found the right option!

Tisha

[stoneaxe]

It's so frustrating that what we are faced with seems to be more sales pitch than unbiased medical opinions. I was treated with the Proton in Boston...have mixed feelings about the results. I've had lots of problems....would they have been as bad with CK?....I don't know....quotes from Dr. Medbury certainly would make you think not.

http://anausa.org/forum/index.php?topic=5996.msg56167#msg56167

All that and my tumor has recently increased in size.