gamma knife vs. cyber knife

Discussion in 'Radiation Oncology' started by drpainfree, 05.18.14.

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  1. drpainfree

    drpainfree 7+ Year Member

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    I have a patient with lung ca with compression of bronchus. I'd like to get some inputs from my fellow rad-onc specialists,
    - what're the differences between gamma knife treatment vs. cyber knife treatment?
    - what're the differences between cyberknife VSI (5th generation) and cyberknife M6 (6th generation)?
     
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  3. stems

    stems Banned Banned

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    You know that info is pretty easily found on the internets...

    You can't treat lung cancer with gamma knife, it's only for brain. No real difference between the gens of Cyberknife.
     
  4. drpainfree

    drpainfree 7+ Year Member

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    Thanks for the quick pointer.

    My understanding is that older generation cyber knife requires gold marker to be implanted at tumor site. The patient cannot tolerate this procedure. the newer generation of cyberknife doesn't require gold marker from what I heard. Therefore the question, does VSI and M6 both offer the alternative from gold marker implantation? If they both do, what's the advantage of M6?
     
  5. ramsesthenice

    ramsesthenice 2+ Year Member

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    Not an easy question. Cyber knife can be done without fiducials (and I do it with some frequency) but that's not to say it always should. The Xsight systems are good for some lesions but if they move too much your better off doing image guided linac based SRS. This is a very technical question without much data for clinical outcomes.

    In this case compressing a main bronchus, why do you want to use radio surgery and not just palliative standard fractionation? CK at a major airway is tricky.

     
  6. medgator

    medgator Senior Member 10+ Year Member

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    Or at least some modest hypofractionation depending on your risk tolerance. Even with bronchial compression, I wouldn't do palliative doses if it was a non-metastatic situation.

    I don't think this type of case would be good for SRS/SBRT and would personally do 70000 in 28-35 Fx on a standard linac with IGRT (kv/CBCT).

    Def not a cyber case IMO (still trying to figure out how Gamma Knife was brought up).
     
  7. Gfunk6

    Gfunk6 And to think . . . I hesitated Lifetime Donor SDN Moderator 10+ Year Member

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    The older versions of Cyberknife software required multiple fiducial markers to be implanted for 'real-time' tracking of the tumor. However, newer software has the 'Xsite' package for lung. This allows treatment without fiducials but the core requirement is that the tumor must be visible by the stereoscopic imaging the CK uses for image guidance. When you have peripheral tumors (e.g. a solid mass surrounded by air) then Xsite is quite useful. In central locations, containing the mediastinum, vascular structures, etc. Xsite might not be possible.

    VSI generally cuts down treatment time. In older versions of CK, when one used two or more collimator sizes, the rad techs had to stop the machine, enter the vault, remove the first collimator and mount the new one. With the 'retina' technology of VSI, the collimator can be changed instantly, thereby obviating the need for collimator replacement and thereby speeding up treatment. M6 ups the ante by using a multi-leaf collimator to 'shape' the beam. It seems to me that the benefit of doing this would be fairly marginal given the large number of non-coplanar beams that the CK system uses anyway.
     
  8. drpainfree

    drpainfree 7+ Year Member

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    Thank you all for the explanation. They were very helpful. The patient is not a resident of U.S. and his oncologist/rad-oncologist suggested CK 6th generation for the bronchus-compressing tumor. I don't know the extent or the stage of his lung CA at this point. The patient is considering the option of coming to the States for CK treatment.

    Please kindly clarify a few key points,

    1. why is it tricky to treat a bronchus-compressing tumor with CK?
    2. why is it not CK case but would rather go with standard linac? Here the issue is the frequency and duration of treatment visits being as an out-of-country visitor if he does choose to come to the States for the treatment. Obviously, the shorter and the quicker, the better
    3. Is there any harm with using CK with this case?
    4. CK VSI vs. CK M6, both offers Xsight? Neither requires fiducial marker implant? Therefore there is no advantage using CK M6 over CK VSI?
     
  9. RadOncDoc21

    RadOncDoc21 5+ Year Member

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    The answer is not as straight forward as it seems.Toxicity is the main issue with a centralized lesion using SBRT. Although it's more convenient, it could come at a cost.

    I've never used cyberknife so can't comment on the models.
     
  10. RadOncDoc21

    RadOncDoc21 5+ Year Member

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    Sorry duplicate post.
     
  11. Gfunk6

    Gfunk6 And to think . . . I hesitated Lifetime Donor SDN Moderator 10+ Year Member

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    Relatively high rates of fatal hemoptysis have been reported in an area 2 cm around the carina/main bronchi (the so-called 'Timmerman zone').

    Generally speaking, SBRT with a standard linac is much faster than CK (generally about 50% faster per fraction). The number of fractions would probably be the same (five).

    Would have to see 3D imaging to comment. I don't think it would harm the patient necessarily, but it may not offer any benefit.

    Again, would have to see the 3D imaging to comment.

    I assume your friend would be paying out of pocket for SBRT which would run in the $15,000 - $20,000 range. This is probably not worth it. Assuming he/she is coming from a developed country - he/she would likely get more 'bang for their buck' being treated by linac-based SBRT locally.
     
  12. Palex80

    Palex80 RAD ON 7+ Year Member

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    This is palliative, right?

    I suggest 5 x 4 Gy, 3D
     
  13. medgator

    medgator Senior Member 10+ Year Member

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    It depends on whether this is metastatic vs non-met lung CA.
     
  14. drpainfree

    drpainfree 7+ Year Member

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    thank you all for the input. a few clarifications,

    - the metastatic status is unknown to me at this time. regardless though, the patient needs to treat the bronchial compression issue.
    - the cost is not an issue as long as it's under $50k
    - not possible for any type of invasive procedures for fiducial implant due to high risk of bleeding (severe thrombocytopenia)

    what is "Timmerman zone"? what's the risk of bleeding with either CK or SBRT for a bronchus-compressing lung tumor? This would be a yes-or-no question for the patient to decide whether or not to proceed.

    It seems SBRT with standard linac over CK is suggested a few times. What is the advantage of SBRT over CK? My understanding of SBRT and CK are both stereostatic body technique, one uses robotic arm to track position, the other uses a mold. Is SBRT significantly cheaper? If the cost is not a big issue, are there any other benefits? Sounds like it's also faster?
     
  15. RadOncDoc21

    RadOncDoc21 5+ Year Member

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    I think the proper staging and workup should come first before he sees a Radiation Oncologist... outside of that, everything else would be hypothetical and almost unethical.
     
  16. drpainfree

    drpainfree 7+ Year Member

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    I believe it has already been completed locally and the patient is specifically seeking radiotherapy for alleviating the bronchus-compression symptom. I agree that he probably needs more work-up and staging studies here in the States. On the other hand, the patient has to decide whether or not it is worth to come over from oversea for the treatment, not work-up.
     
  17. RadOncDoc21

    RadOncDoc21 5+ Year Member

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    Assuming he has Stage I NSCLC- somebody bold might offer him definitive SBRT- RTOG 0813 and is currently closed in which they are investigating the tolerance dose to these central lesions. The "Timmerman zone" is the 2 cm proximal tree that has been shown to have increased toxicity associated with SBRT that GFunk talked about.

    If he has Mets of anything other than Stage I NSCLC- His best best is for palliation which he could have done anywhere and I would advise him to save his money and time (which is most important).
     
  18. napoleondynamite

    napoleondynamite Keepin' it real yo 10+ Year Member

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    At the Spring Refresher last year data was presented from the Netherlands for central SBRT I think it was 7-8Gy per fraction for 7 fractions with excellent late toxicity profile..has anyone adopted that fractionation? I'll see if I can dig up the reference. But the guy presenting was from Penn and indicated it was his go-to regimen.
     
  19. drpainfree

    drpainfree 7+ Year Member

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    Just got a few more details, CT showed mass lesion at the left hilum. PET scan didn't reveal apparent mets. Pathology from recent hemoptysis points to squamous cell carcinoma.

    We don't know about nodal involvement. Assuming there's positive nodal involvement, is SBRT or cyberknife not indicated? Why?
     
  20. Gfunk6

    Gfunk6 And to think . . . I hesitated Lifetime Donor SDN Moderator 10+ Year Member

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    Seminal 'Timmerman zone' paper = http://www.ncbi.nlm.nih.gov/pubmed/17050868

    We don't treat nodal disease for SBRT due to high risks of toxicity to mediastinal structures. Also, much higher risk of systemic failure with positive nodes.

    CK > linac-based SBRT, impossible to say without seeing 3D imaging.
     
  21. Palex80

    Palex80 RAD ON 7+ Year Member

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    If this is a primary Stage I-II NSCLC with a left hilar mass (without mediastinal involvement) then standard of care would be curative surgery.
    If the patient is too unfit for that (or the procedure would require a pneumonectomy, for which the patient does not qualify), then primary RT (possible combined in chemo for Stage II disease) would be standard of care.

    I would offer a fit patient SBRT in this situation. The 3 x 20 Gy schedule is not an option, but more fractionated SBRT schedules with 5 - 10 sessions are well suited.

    We actually give 5 x 8 Gy on the PTV using a 60% isodose prescription which leads to 5 x 13.33 Gy to the GTV.
    Sometimes we include the entire hilus in the first 3 fractions as CTV just to make sure we don't miss any microscopic spread in other nodes and then boost the primary for the last couple of fractions.

    If there's N2 involvement then its palliative, unless the patient can undergo radiochemotherapy with a platinum-based doublet.
     
  22. Palex80

    Palex80 RAD ON 7+ Year Member

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    I am not aware of ANY situation where CK > linac-based SBRT.

    What's better with CK?
     
  23. RadOncDoc21

    RadOncDoc21 5+ Year Member

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    I think it works better in California. Doesn't seem to work anywhere else. :)
     
  24. Gfunk6

    Gfunk6 And to think . . . I hesitated Lifetime Donor SDN Moderator 10+ Year Member

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    Touche, Palex, Touche.

    I agree in most cases the differences would be minor. However, there is some retrospective evidence supporting better dose distribution with anterior tumors.

    Overall, I agree that given the innovations of a modern day linac, lack of flattening filter (2000 MU/min), 3-5 mm MLCs, and gating, the 'benefit' of CK will grow ever smaller.
     
  25. medgator

    medgator Senior Member 10+ Year Member

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    I've always felt like CK is a big "black box" where you are basically trusting the robot to do its thing. I guess it is all personal preference... I like CBCT with fluoro cine imaging during treatnents to see what is going on.
     
  26. Lamount

    Lamount 2+ Year Member

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    Are there any situations in which a gamma knife or cyber knife have significantly better outcome data than modern linac (I.e. Truebeam stx) based SRS or SBRT, respectively?
     
  27. ramsesthenice

    ramsesthenice 2+ Year Member

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    Out one as in local contol? Doubtful. We do a lot of Cyberknife and I think most of the advantages are theoretical. If you get good tracking with fiducials the volume of lung getting full or near full dose should be smaller but is that worth a double treatment time? Is it clinically meaningful? Maybe maybe not.

    I think the place CK stands out is when you need really low CIs like in the retreatment setting very close to sensitive structures (like cord). We also treat a fair number of prostates with CK 9.5 x 4 with very low toxicity (and very low CIs).

    For bread and butter though, I don't Think there will be much meaningful data CK or GK is better than Linac for SBRT or vice versa.
     
  28. erectorspinae

    erectorspinae 2+ Year Member

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    Are you treating prostates like this off of protocol?
     
  29. ramsesthenice

    ramsesthenice 2+ Year Member

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    It was on protocol but now closed. Stanford has 8 year follow up for prostate CK. Someone published 10 year data (I think King was the lead author, could be wrong though). Seems to work real well and toxicity has not been an issue. Probably treat a couple per month. Have for several years now.

    Caveat: only treat LR and low vol IR patients.
     
  30. Palex80

    Palex80 RAD ON 7+ Year Member

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    I don't see the point in treating prostaste with Cyberknife. What's the benefit of CK for prostate in comparison to modern Linacs? I only see disadvantages.
    You don't have cone beam CT, which means you can only use the fiducials to find your target and don't have any information on the rectum. Plus you can't do any king of adaptive planning, which is becoming more and more of an issue nowadays.

    Cyberknife was great a couple of years ago, when dynamic IMRT, modern couches, cone beam CT, Calypso, etc... were not available. Nowadays it only has a catchy name, if you ask me.
     
  31. ramsesthenice

    ramsesthenice 2+ Year Member

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    The benefit is convenience to the patient. They are treated in 4 sessions, not 42. That is a big draw to a lot of people. As I said, we are selective in who is treated this way but our experience (about 5 years now) and the data in the literature looks pretty promising. There is no evidence for excess toxicity (GI or GU).
     
  32. Gfunk6

    Gfunk6 And to think . . . I hesitated Lifetime Donor SDN Moderator 10+ Year Member

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    I think Palex is suggesting that we can also perform prostate SBRT with a linac. If you compare treatment with a Trubeam STX or Versa HD, treatment will still be four fractions but treatment will be MUCH faster and it will be 3D image guided. What precisely is the benefit of CK?
     
  33. Chartreuse Wombat

    Chartreuse Wombat 2+ Year Member

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    To my knowledge there is no 10 year data on SBRT for prostate. King has published paper in Green Journal of >1000 patients with median FU of 36 months in CK consortium. About 135 patients followed for 5 years.
     
  34. medgator

    medgator Senior Member 10+ Year Member

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    The CK proponents will tell you that the CK, while lacking 3D volumetric imaging, makes up for it with real-time robotic tracking for "intra" fraction motion. A linac won't have that (unless you do calypso, but even then, the linac won't adjust like a robot to the changes in the beacons). As to how that affects the clinical outcome, who knows. It is my understanding that most of the longest data out on SBRT for prostate has come from the CK. Are people just extrapolating it out to standard Linac-based Tx with OBI? Is such an approach valid without the "real-time" tracking?

    I personally don't do prostate SBRT at all, and with the recent experiences coming out on hypoFx for prostate CA, I am even less interested in it now, let alone hypofractionation.
     
    Last edited: 05.21.14
  35. ramsesthenice

    ramsesthenice 2+ Year Member

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    Yea, I waffled on King above and its certainly not the data I was thinking. Someone pitched us 10 year data at some point. I admit, can't find it on pubmed or anywhere else so we can scrap that for now. Six year results on a 315 patient study are available, appears to be the longest published follow up.

    Misunderstood him. I havn't tried it (we don't have the goods for it) but I bet you could. As I said above I think most of the advantages are theoretical but there are a couple. One potential advantage is better conformality that you get from using hundreds of beamlets to deliver the radiation (at the expense of a long treament time). The other, as gator pointed out is the tracking issue which does allow you to use tighter PTV margins. Theoretically, these could allow you to treat some cases where the rectum is too large or proximal. In practice does this really pan out? I honestly think the CK does allow you to treat some men you wouldn't be able to do with linac based SBRT BUT they are the minority of cases. I agree if you wanted to in many cases you could come up with a good plan and safely treat with something like a Truebeam and do it a hell of a lot faster (and in those cases that would potentially be the better option).
     
  36. ramsesthenice

    ramsesthenice 2+ Year Member

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    To be clear, I initially brought this up to discuss possible uses of CK. I am certainly not advocating for the wide spread use of SBRT for prostate cancer. Quite the contrary. I think it has its place in very selected low risk, low volume patients. Using it for high volume or hight risk patients scares me for the same reason that doing an RP for a lot of high risk patients is dicey which is the high risk of microscopic extraprostatic disease. The treatment margin in conventional IMRT is really important in these cases and what I think makes it a better option than surgery which will inevitably show pT3 disease and require adjuvant (saldy, more often salvage) RT. By trimming down on margins for radiosurgery I bet you would end up encountering the same problems.
     
    Last edited: 05.22.14
  37. Palex80

    Palex80 RAD ON 7+ Year Member

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    Tracking with CK may be cool, but it can be done with LINAC-based SBRT approaches too. You don't necessarily need Calypso for that.

    Brainlab for example does offer a KV-based real-time solution for this on their Novalis system.

    I am not persuaded that the dose distribution with cyber knife is better than with modern dynamic IMRT, especially if you are using some of the newer thinner MLCs like the Elekta-Agility for example.
     
  38. drpainfree

    drpainfree 7+ Year Member

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    Looks like this thread has blossomed into a nice discussion of cyber knife vs. others. I truly enjoyed your information and hope it will be helpful for my own practice in the future.

    Back to the original post, does it matter if the patient have NSCLC vs. Small Cell LC assuming both are early stage without mediastinum involvement?
     
  39. Palex80

    Palex80 RAD ON 7+ Year Member

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    I am not aware of any data on SBRT or CK for SCLC. I would definitely electively treat mediastinal nodes in a hilar SCLC. Not enough evidence to suggest otherwise. Furthermore RT alone is palliative even in early stage SCLC. You need chemo to cure this disease.
     
  40. medgator

    medgator Senior Member 10+ Year Member

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    I was unaware of that.... does the linac "move" several times a minute to respond to patient/tumor motion?
     
  41. Palex80

    Palex80 RAD ON 7+ Year Member

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    A google search can work wonders, here's the UCLA-page on their system
    http://radonc.ucla.edu/body.cfm?id=76
     
  42. medgator

    medgator Senior Member 10+ Year Member

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    I do see adaptive gating being mentioned which obviously will help with lung and liver but I do not see anything discussing tracking outside of those sites (I.e. prostate)
     
  43. Palex80

    Palex80 RAD ON 7+ Year Member

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    http://radonc.ucla.edu/body.cfm?id=244

     
  44. medgator

    medgator Senior Member 10+ Year Member

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  45. Neuronix

    Neuronix working like a dog SDN Advisor SDN Administrator 10+ Year Member

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    We use this. It doesn't "track" and adjust the plan, but rather if there is patient motion, the treatment is interrupted. The reality is that significant motion is rarely an issue even with frameless SRS in adults, but it's good to have a realtime system monitoring as a failsafe. The gamma knife shops swear to me that they would only treat single fraction SRS with a rigid head frame, but that of course sounds barbaric to me now seeing our current system and results.

    I'd love to actually see the plans compared. My suspicion is the conformality indices would be quite similar, and whatever difference is probably not of clinical relevance.

    Our arc plans for prostate take about 1-2 minutes to deliver. We align to plain gold seed fiducials and start the arc immediately. With PTV margin, intrafraction motion is practically irrelevant on this time scale. We do a lot of SBRT liver treatment in the same fashion. With ITV/PTV, typically the liver can be safely treated accounting for respiratory motion, and typically much faster than with CyberKnife. However, if there is too much respiratory motion or the tumor is too big to treat with an ITV, you still don't need a CyberKnife. Just respiratory gate it with a respiratory tracking system. The treatment time still comes out fairly similar to a CK.

    Neither of these scenarios are appropriate for SBRT (assuming that the early NSCLC is compressing a major bronchus). This thread is raising my eyebrows for two reasons.

    1) SDN forbids personal medical advice to begin with. Due to liability, we are not supposed to be providing any medical advice on this site.

    2) You have provided so little of the details of the case, that it's hard to know what the most appropriate modality is for the care of this patient. The patient needs a formal consultation. If the patient wants to travel and have a formal consultation, have them pick a major center (i.e. a NCI designated cancer center) based on whatever measures are most convenient such as distance and just go there. The expertise of a lung specialist radiation oncologist (available at any major cancer center in the USA) far outweighs whatever benefits of whatever technology they have available at their site. i.e. Having the best hammer does not make you the best carpenter. Further, if this patient has compression of a major bronchus due to lung cancer, they may need treatment sooner rather than later, which means deliberation on where to be treated should be short. Your patient likely needs consultation and radiation treatment with haste, not after detailed discussion of radiation technology.
     
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  46. medgator

    medgator Senior Member 10+ Year Member

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    That was a Helpful discussion, thanks.

    As far as single fraction srs for brain mets,I agree no need for a rigid frame. My gut still gets nervous when I hear people consider treating trigeminal neuralgia without rigid fixation (doses of 85gy+ near the brainstem with gk).

    It's clear that linac based srs has really advanced to a point to make elekta and accuray nervous about their gk/ck products I imagine
     
    Last edited: 05.24.14
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