RadOnc and the Gamma Knife

Discussion in 'Radiation Oncology' started by RunDMCMD, May 9, 2008.

  1. RunDMCMD

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    I am a newbie interested in RadOnc.

    Can you guys please tell me what role a RadOnc plays during a gamma knife procedure ? Does he/she assist the neurosurgeon ?

    Can RadOncs do a neuro procudure with the Gamma knife without the n-surgeon ?

    Can RadOncs do non-neuro Gamma knife procedures without cooridation with other surgeons ?

    I would appreciate a discuss/education on RadOncs and the Gamma knife.

    Thank you.
     
  2. Gfunk6

    Gfunk6 And to think . . . I hesitated
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    There is some institutional variablity. Generally (at large, academic institutions) the process goes something like this:

    1. Patient shows up
    2. Neurosurgeon affixes sterotactic head frame
    3. Pt undergoes MRI brain w/ head frame
    4. Radiation Oncologist draws volumes based on MRI
    5. Neurosurgeon double-checks volumes w/ modification if needed
    6. We also like an official Neuro-Radiology read
    7. Physicist makes plan and comes up w/ dose distribution
    8. Pt is placed into the GK unit
    9. Beam on!
    10. Neurosurgeon removes head frame and bandages wound sites

    Legally? I don't know. But I would not.

    See above. Surgeons should be involved.
     
  3. SimulD

    SimulD Senior Member
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    Interestingly, although most rad-oncs do not place the frames, they can remove the frames and bill for that (learned that at the course). I'm not sure why we don't place the frame. During our rotation, we can learn how to do that. It's not very hard, really, but I wouldn't really want to do it.

    ALL GK-SRS cases at our institution (that does perhaps more than any other institution) are done in concert with the surgeon. They are seen in a collaborative clinic, usually the day (or a few days) before the case.

    Interestingly, the indications for CyberKnife SRS are the same (acoustics, mets, meningioma, TN, etc.), however these cases can be done without a surgeon (although most are done collaboratively). I think it does not have as much to do with the frame as it does other issues.

    I think the main reason to include surgeons is to facilitate the referral of patients. Surgeons are not allowed to be authorized users for GK or CK, nor do they have as much training as us with radiation therapy. They can walk away during a GK case, but the rad-onc and physicist cannot. I can't imagine thinking that we would need a NSG to help me with a case. But, I know without their referrals, we wouldn't get very many cases. I think it makes care more expensive for patients, but what can you do? Such is modern medicine.

    -S
     
  4. Gfunk6

    Gfunk6 And to think . . . I hesitated
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    Also as a note of historical interest: both the GK and CK were invented by neurosurgeons.
     
  5. PimpMyRad

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    SimulD hit the nail on the head. You really don't need a neurosurgeon to do it, but you won't get many referrals unless they are involved. Legally, they can't do it without us because the GK has cobalt sources, and there needs to be an official user as defined by the NRC involved in the tx delivery.

    I know of one academic institution where the neurosurgeons drive the program from start to finish, and the role of the rad onc is to just sit there while the neurosurgeon does everything. The rad oncs don't even participate in pt selection, and i know are appalled by some of the pts that are treated. I have seen pts who had up to a dozen brain mets gamma-knifed - unbelievable and unconscionable. Lately, I've noticed a new trend: for a solitary met, the neurosurgeon removes it, and then does GK to boost up the operative site "just in case", but doesn't refer for whole brain RT. I know there is controversy on whether to do whole brain RT, but I can't see the value of resection AND gammaknife - one or the other should suffice.

    But the GK is a huge revenue center, and as long as the bucks keep rolling in, no one can or will challenge the neurosurgeons. Just my jaded opinion, I could be wrong. Anyone else have any observations about the GK?
     
  6. temujim

    temujim Junior Member
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    In order:

    Rad Oncs are the authorized user, meaning that the procedure cannot happen without us. So neurosurgeons assist us.

    Yes, but this is rare

    Of course.

    This issue is a turf battle. Neurosurgical groups regularly petition medicare to cut us out. I encourage everyone to read Kondziolka's presentation to the NRC in 2005 regarding his view of radiation oncology (which is highly insulting). It can be found at (www.nrc.gov/reading-rm/doc-collections/acmui/tr/2005/tr042105.pdf)
     
  7. stephew

    stephew SDN Super Moderator
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    actually the removal is where you need the neurosurgeon most. If you happen to have hit a superficial artery, which happens (ive seen in 4 times), you dont know until you remove the frame and you want a stitcher there.

    I used to put the frames on in residency under the supervision of the surgeons.

    The frame is a billing issue hence the concerns about frameless among the community.

    The role of the surgeon (ie if they do review the plan, help with contours etc) varies place to place. I agree that its good to have a neuroradiologist involved in a good number of cases.

    Keep in mind the prominance of the surgeon is in part due to the historical aspect of a surgeon developing the platform.

     
  8. stephew

    stephew SDN Super Moderator
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    There has been very interesting evidence of very b ad outcomes in the cases where radiation oncologists are not intimately involved with radiosurgery. Neurosurgeons are not radiation oncologists any more than we are neurosurgeons.

    But given the high doses of radiation and the need for physics, I dont expect this to happen without radiation oncolgoists. Another reason: Radoncs are the ones who can determine if srs is appropraite from a radiation-medical standpoint. Neurosurgeons are not trained in the fundementals of radiation and so dont know about different fractionation schemes and planning and which are appropraite. Thus they can't make the upfront decision about what to do. so radonc must be involved in this. They might get a sense of it but dont have the expertise.

    (I can tell which lesions are likely surgically accessible but I am not the expert) However this is a medical argument and unfortunately takes a backseat to the financial issues.
    Neurosurgeons stay involved for the billing. Radoncs are marginalized in some centers in spite of the multitude of medical reasons to be involved.
     
  9. radonc

    radonc Senior Member
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    the benefit of boosting the post-op bed is that you are effectively able to reduce the 'true' local recurrence rate to <10% and spare up to 70-80% of patients who would have gotten WBRT from getting WBRT. of course, this is dependent on the histology, kps, etc.


    --------------------



    http://www.ncbi.nlm.nih.gov/pubmed/18183353

    http://www.ncbi.nlm.nih.gov/pubmed/17881139
    Stereotactic Radiosurgery Alone and Primary Resection Followed by Adjuvant Stereotactic Radiosurgery
    in the Treatment of Limited Brain Metastases
    M. Quigley, S. Karlovits, B. Karlovits, J. MacKenzie, M. Johnson, A. Colonias, R. Fuhrer
    Allegheny General Hospital, Pittsburgh, PA
     
  10. stephew

    stephew SDN Super Moderator
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    there is the first data with regard to doing this in the red journal recently. However a couple of points:
    1) to make it effective you may need a margin
    2) as per a paper recently published about margins on tumors that are intact, this is not safe (the first paper doesnt have enough durable data on the toxicity issue though they attempt to address it).
    3) I tend to prefer srt to a tumor bed when im not giving WBRT. SRS i reserve for special cases (ie resistant histology, non eloquent area etc).

    BTW that <10% data is only if youre looking in the first 12 mos. if a pt has had a solitary or single met to brain and is s/p resection, they may very well live more than 12 mos and the control dips.
     
  11. radonc

    radonc Senior Member
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    true, but they dont live more than 16 mo or so...but for that 1st year, you know you have durable control of disease at the primary site...and you can reserve wbrt for salvage.

    what fractionation do you SRT the postop bed with?
     
  12. SimulD

    SimulD Senior Member
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    The tumor bed boost with SRS is almost becoming 'standard' without any data, except that Stanford series. Pitt's series will be published soon. I think at the GK meeting last year, like 75% of the docs were doing it. >10 mets are being treated quite frequently, especially at places with the Perfexion unit, where 13 mets can be treated in 90 minutes. Old Japenese series of patients with many (5 - >20) mets and assessing dosimetry showed the whole brain may get a mean dose of 4 Gy. If the whole brain is getting 4Gy or more, what's the point of deferring WBRT?

    On the in-service exam this year question about what do s/p resection of a solitary met. A) WBRT B) SRS boost c) nothing d) both. I think people are doing all of the above.

    If the NSG is your referral source, even if you have questionable situations (multiple mets, boosting the bed, etc.), if you turn them down too often, you get in a bind.

    So you fractionate the bed boost? What dose? What margin - 2mm?
     
  13. radiaterMike

    radiaterMike Junior Member
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    On the in-service exam this year question about what do s/p resection of a solitary met. A) WBRT B) SRS boost c) nothing d) both. I think people are doing all of the above.


    That has to be the worst question ever (well ... maybe not) since every and any answer is correct. I asssume WBRT is the answer that was 'correct' but you can make arguments for any of these.
     
  14. medgator

    medgator Senior Member
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    I think the histology is going to play a big role in the concept of an SRS tumor bed boost. Boosting a solitary NSCLC met site vs. Breast met site may show different outcomes. On average, the breast CA pt with brain mets may live longer, and may have a lower incidence of global brain metastases. Some believe the idea of trying to delay WBRT for NSCLC is folly because there may be subclinical disease throughout the entire brain at the onset (similar to what is known for SCLC).

    It's a shame that RTOG had to close the PCI trial for NSCLC. It may have provided some insights regarding this question.
     
  15. stephew

    stephew SDN Super Moderator
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    no, its not standard. It is more common but hardly standard.

    The data of doing >20 mets is as you say not a US standard and it makes no sense as a generalization. If you have that many, you need to sterilize the brain. Do WBRT and boost IF that makes sense later.

    I had a pt who had WBRT with a lot of disease. The pt then received radiosurgery elsewhere as I recommended against it. I will not go into details regarding why. Several months later this person neeeded repeat WBRT. I had to pull back the dose because they had a high integral dose from the SRS. It helped for a few months. Would higher dose have helped more? Who knows. But doing srs because you can is bad practice.


    The inservice exam you had is a completely inappropriate question. The "right" answer is WBRt but you could do any of it (i wouldnt do "nothing").

    I tend to fractionate with great success. I can safely put on a margin without significant risk of toxicity. 2mm is a good rule of thumb-of course I qualify this with the reality that you must look at the specifics. The dose: typically 300x10. This way I am essentially giving the wbrt dose for microscopic disease to the cavity. you could go higher quite safely in many cases.

    As for the neurosurgeons, good ones will listen to your rationale.They will be concerned with the best for the patient. Developing relationships is the key. Of course if its not possible - sometimes people have other interests, or simply disagree- you must always remember nevertheless to make your decisions based on the interests of the patient. Explain your reasoning to the patient. Sometimes offering them the choice of both is reasonable.

    Dont forget: youre a doctor, and you make decisions that are best for your patients. I am happy to be in a place where my views are respected and I dont have to worry about the financial considerations of referrals and that particular sort of politics. Its a real issue out there. Academic politics are simply different.

     
  16. stephew

    stephew SDN Super Moderator
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    There is a paradox. We like to withhold WBRT to the "young" and those who will live longer. however they will tolerate WBRT typically much better than the older.
     
  17. qwert

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    Well the data on adjuvant SRS just came out - see above.

    Also, from what I know, standard of care is still to limit SRS to <= 4 mets.

     
  18. medgator

    medgator Senior Member
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    I thought it was < or = to three mets based on the RTOG trial 95-0 whatever it was.....
     
  19. SimulD

    SimulD Senior Member
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    I said 'standard' in quotes (for tumor bed boost) ... I know it's not SOC, but so many are doing it.

    What I've seen a fair amount of recently is resection of a dominant lesion and then SRS to the bed and the other lesions. Based on nothing, of course.

    S
     
  20. IndyXRT

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    Aoyama et al (Jama, 2006) published a smaller (n = 132 vs. 333 for RTOG 95-08) randomized trial of SRS +/- WBRT (essentially the reverse of the RTOG trial). They allowed 1-4 brain metastases. There was no difference in survival, but local control was improved with the addition of WBRT. I believe it is because of this trial that some will give SRS + WBRT to patients with 1-4 rather than 1-3 metastases.
     
  21. medgator

    medgator Senior Member
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    Oh yeah --- man its so easy to forget the fine details when you have to know 39593593 trials in your head.

    Their data contrasted with RTOG, which did find an OS benefit in RPA I patients wtih a solitary met and lung CA histology, and a PS benefit for pts with 1-3 mets at 6 mos.

    I feel like it is diminishing returns when we are gamma-ing >10 mets or so (except maybe in the resistant histologies in pts with a good PS and controlled extracranial disease). The policy of withholding WBRT upfront and trying to spot weld with SRS as lesions pop up is also interesting considering the RTOG study which gave upfront WBRT to everyone with 1-3 mets. I guess the JAMA study lent support for the reverse.
     
  22. stephew

    stephew SDN Super Moderator
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    many do live 18 mos or long. Not the majority, but a lot. I typically do 300x10 or 12 to the post op bed. One could probably safely hypofractionate as if there was a lesion there: so <3cm 500 x 5. It seems reasonable that if you can do srs to the cavity you can use the hypofx dosing to the bed. but ive not done that, and if you just do 300 x 10 and there is a local relapse, you can boost without worrying about dose modificiation.
     
  23. stephew

    stephew SDN Super Moderator
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    an important thing to note about that data- unlike patchell, these pts didnt have well controlled disease. either in brain or extra cranially.
     
  24. SimulD

    SimulD Senior Member
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    Results of RTOG 9508 would have been more reassuring if treatment arm came out as a significant factor in multivariate analysis ...

    S
     

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