Experts Debate CyberKnife for Prostate Cancer and other stuff

bdhilton

Experts Debate CyberKnife for Prostate Cancer

While its advocates say the CyberKnife offers prostate cancer patients a safe and effective -- and much more convenient -- alternative to traditional radiation treatment, many experts fear that it could leave many men unnecessarily vulnerable to recurrences or potentially serious complications.
"This is really pushing the envelope," said Anthony L. Zietman, president-elect of the American Society for Therapeutic Radiology and Oncology (ASTRO). "It might be as good and more convenient. It may be better and more convenient. But it could turn out to be a disaster. No one knows."

http://www.washingtonpost.com/wp-dyn/content/article/2008/11/27/AR2008112702186.html


Debate surrounds new prostate-cancer treatment: Philadelphia Inquirer
http://www.facebook.com/note.php?note_id=121129041372


In prostate cancer, new treatments delivered by expensive machines have been embraced without large head-to-head comparisons of effectiveness. To further complicate matters, doctors on both sides say the arguments are clouded by ownership interests in various machines and other financial incentives…

Medicare debates paying for noninvasive Cyberknife treatment of prostate cancer

Perman said the Medicare advisory committee is looking at Cyberknife outcomes based on older data and nothing that’s been available since fall 2008.

There have been five published studies since then involving outcomes of 500 men, including patients from Naples who were part of a study when the NCH Healthcare System purchased a Cyberknife in 2004, Perman said.
“That is what bothers me,” Perman said.

The local study was conducted by Dr. Debra Freeman, formerly with NCH, who relocated to Tampa after NCH sold its Cyberknife system to 21st Century
Ohttp://www.naplesnews.com/news/2010/apr/20/medicare-debates-paying-noninvasive-cyberknife-tre/ncology.

CYBERKNIFE® PROCEDURE
There is some evidence to support the idea of hypofractionation, but overall it cannot be denied that the procedure is experimental. Hypofractionation may well have merit, but long term (>10 year) results are not available for HDR Brachytherapy, which has been practised since about 1997, and neither long nor short term (>5 year) peer reviewed results are yet available for CyberKnife®. Maybe in the long run, CyberKnife® will prove to have similar (but possibly not better) outcomes vis-a-vis non-hypofractionated EBRT (External Beam Radiation Treatment), in which case, its selling point will be convenience.

Any man considering Cyberknife® should make sure that his is a truly informed consent, and that he has chosen it over methods with established records.

http://www.yananow.net/cyberknife.htm


Sorry the only positives I am reading are published by hospitals and doctors that have bought this $4Million ++ piece of equipment…

Robert1941

question
are you saying, bdhilgton, that this cyberknife is dangerous and just an experiment? why would they sell this treatment? what should someone who doesn't know all this tuff do?

i was going to check it out but now I wonder,.

Kongo

here we go again
Despite what the title of this thread might imply, that there is some new and current debate going on about CyberKnife, it is instead a remix of his previously posted threads and edited news stories that are almost three years old. No orginal thoughts here.

As usual with this poster who has an obvious axe to grind, his post is a mishmash of dated news stories, including a Facebook post, which he has cherry-picked to highlight material he believes to be negative about CyberKnife SBRT treatment of prostate cancer and trying desperately to somehow imply that this FDA approved procedure is somehow experimental and dangerous. His timing in bringing all of this up again is nothing more than a pathetic attempt to downplay recent posters who have successfully completed CK treatment or posted updates to their treatment.

All of these stories have been edited by the poster to delete material he chooses not to include and which he apparently assumes will bolster his arguments. I presume he feels, as usual, that he is “just stating the facts” It reminds me of the negative campaign ads now on TV where politicians from both parties take quotes and actions out of context to try to smear their opponents.

The author conveniently ignores recent studies and coverage beyond 2008. As usual, he also fails to provide any conclusions he as an individual brings to the debate and avoids injecting any critical reasoning behind his agenda.

One very recent study which has not been edited or plagiarized that may be of interest to readers who are interested in this treatment option was published this month and can be found at

http://www.tcrt.org///mc_images/category/4309/04-katz_tcrt_9_5.pdf

Swingshiftworker

Robert1941 said:

question
are you saying, bdhilgton, that this cyberknife is dangerous and just an experiment? why would they sell this treatment? what should someone who doesn't know all this tuff do?

i was going to check it out but now I wonder,.

CK is Not Dangerous or Experimental
Robert:

I would never have undergone CK treatment if it was in anyway considered dangerous or experimental.

CK treatments have been approved by the FDA and have been used for many different types of "untreatable" cancers -- lung, brain, spine, etc. (as well as otherwise treatable prostate cancers) and has successfully "cured" people who had no other possibility of survival. With CK, you are given as good or better a chance of a "cure" for PCa without all of the potentially AWFUL side effects of surgery, as well as the less damaging side effects from radiation by conventional methods.

The CK protocol is extremely precise and the calculated margins for CK treatment are only 5mm -- that means no more than 5mm of tissue adjoining the prostate (like the rectum) should receive any radiation during treatment, which far exceeds anything possible w/other methods of radiation treatment (including BT, IMRT and EBRT). I believe it is also more precise and accurate than surgery in minimizing collateral tissue damage because in CK everything associated w/the prostate's structure can be seen and mapped by CT and MRT prior to and during treatment, but ask any surgeon (open or robotic) and (if he's honest) he'll tell you that it's very hard to discern the precise margins of anatomical structure (eg., where the nerves are, where the rectal/prostate boundary is and which tissue "appears" cancerous or not -- when the surgical site is obscured by blood during surgery. So chances are a surgeon will fail to achieve a uniform 5mm margin when doing the cutting. Of course, a "really good" surgeon can do a really good job for you, but if you get a less than really good surgeon, you can suffer the negative consequences FOREVER. Given this, why risk lesser treatments with potentially greater negative side effects, if you can get a treatment like CK that can cure you with NO recovery time required and with virtually NO side effects at all?

So, IMHO BD's post is pure BS. If you have any doubt, do your own research and find out about it for yourself, but don't rely on what BD has to say on this topic. If you have any questions, you can ask the men here who have received the treatment, including me, Kongo and ViperFred. Although we are obviously "biased" towards CK -- that's because it works and not because we are interested in deceiving others into undertaking a treatment that has no prospects for success.

I just had my treatment a couple of weeks ago, so I personally can't give you any "proof" yet that it works (except for NO recovery time required and no side effects apart from a minor increase in urinary urgency), but ViperFred had his treatment over 2 years ago and his PSA has basically zeroed out and Kongo had his treatment 3 months ago and his PSA has already dropped from around 4 to 1.5 or so, which is amazing. I think these "facts" speak for themselves. As an aside, I can personally also tell you that my sexual performance has actually improved following CK treatment. This is not a common nor anticipated result, but that's what's happened to me so far and I'm not complaining about it (nor suggesting that it will happen for anyone else) as long as my PSA starts to drop like it has for Kongo and ViperFred. However, what is expected for sexual function after CK is performance no worse than before treatment and this has been reported by both Kongo and ViperFred.

As Kong points out, BD's post is a mishmash of old data and doesn't not represent the current state of opinion or demonstrated worth of CK. So, if you're interested in and are an appropriate candidate for CK, you should definitely look into it and find out the TRUTH for yourself.

Kongo

Swingshiftworker said:

CK is Not Dangerous or Experimental
Robert:

I would never have undergone CK treatment if it was in anyway considered dangerous or experimental.

CK treatments have been approved by the FDA and have been used for many different types of "untreatable" cancers -- lung, brain, spine, etc. (as well as otherwise treatable prostate cancers) and has successfully "cured" people who had no other possibility of survival. With CK, you are given as good or better a chance of a "cure" for PCa without all of the potentially AWFUL side effects of surgery, as well as the less damaging side effects from radiation by conventional methods.

The CK protocol is extremely precise and the calculated margins for CK treatment are only 5mm -- that means no more than 5mm of tissue adjoining the prostate (like the rectum) should receive any radiation during treatment, which far exceeds anything possible w/other methods of radiation treatment (including BT, IMRT and EBRT). I believe it is also more precise and accurate than surgery in minimizing collateral tissue damage because in CK everything associated w/the prostate's structure can be seen and mapped by CT and MRT prior to and during treatment, but ask any surgeon (open or robotic) and (if he's honest) he'll tell you that it's very hard to discern the precise margins of anatomical structure (eg., where the nerves are, where the rectal/prostate boundary is and which tissue "appears" cancerous or not -- when the surgical site is obscured by blood during surgery. So chances are a surgeon will fail to achieve a uniform 5mm margin when doing the cutting. Of course, a "really good" surgeon can do a really good job for you, but if you get a less than really good surgeon, you can suffer the negative consequences FOREVER. Given this, why risk lesser treatments with potentially greater negative side effects, if you can get a treatment like CK that can cure you with NO recovery time required and with virtually NO side effects at all?

So, IMHO BD's post is pure BS. If you have any doubt, do your own research and find out about it for yourself, but don't rely on what BD has to say on this topic. If you have any questions, you can ask the men here who have received the treatment, including me, Kongo and ViperFred. Although we are obviously "biased" towards CK -- that's because it works and not because we are interested in deceiving others into undertaking a treatment that has no prospects for success.

I just had my treatment a couple of weeks ago, so I personally can't give you any "proof" yet that it works (except for NO recovery time required and no side effects apart from a minor increase in urinary urgency), but ViperFred had his treatment over 2 years ago and his PSA has basically zeroed out and Kongo had his treatment 3 months ago and his PSA has already dropped from around 4 to 1.5 or so, which is amazing. I think these "facts" speak for themselves. As an aside, I can personally also tell you that my sexual performance has actually improved following CK treatment. This is not a common nor anticipated result, but that's what's happened to me so far and I'm not complaining about it (nor suggesting that it will happen for anyone else) as long as my PSA starts to drop like it has for Kongo and ViperFred. However, what is expected for sexual function after CK is performance no worse than before treatment and this has been reported by both Kongo and ViperFred.

As Kong points out, BD's post is a mishmash of old data and doesn't not represent the current state of opinion or demonstrated worth of CK. So, if you're interested in and are an appropriate candidate for CK, you should definitely look into it and find out the TRUTH for yourself.

Well Said
Well said, Swing. Not only CK but any advice or suggestion on here should be run by your medical team for amplifying information. I believe Robert is near a CyberKnife center at Georgetown which certainly does not engage in experimental or dangerous practices on the men in the DC area. When in doubt, you should always go to the source.

buzzz

Kongo said:

Well Said
Well said, Swing. Not only CK but any advice or suggestion on here should be run by your medical team for amplifying information. I believe Robert is near a CyberKnife center at Georgetown which certainly does not engage in experimental or dangerous practices on the men in the DC area. When in doubt, you should always go to the source.

is cyber knife the best choice?
I'll probably get my head chopped off, but I checked into cyber knife. I was told that the group who invented this took radiation and made a new machine that is given in lesser dosage, and because of that you have less chance of side effects but more of a chance of recurrance. And, I was told that if you have side effects they come much later after treatment. I know of one recurrance, I don't know him personally, I just know of him.

It seems that whatever choice we make we stand by it unwaveringly, it's just normal to not want to hear that it may not have been the best choice. I don't think bdhilton is jealous, I think he sincerely wants to warn others who are just deciding. I believe he also posted a rather grim picture of surgery, which he had. I think he is scared, we all are (or should be), he just shows it more than others.

And it's not fair to suppress infomation for others who are just entering this world. So, bdhilton, keep up the good work, we come here to learn.

All that being said, I had HIFU, and I stand the same as all of you thinking that I made the right choice. I hope we all did, but it takes time to find out, we are all chained to the blood draw for a lifetime for a reason.

CharlieG

buzzz said:

is cyber knife the best choice?
I'll probably get my head chopped off, but I checked into cyber knife. I was told that the group who invented this took radiation and made a new machine that is given in lesser dosage, and because of that you have less chance of side effects but more of a chance of recurrance. And, I was told that if you have side effects they come much later after treatment. I know of one recurrance, I don't know him personally, I just know of him.

It seems that whatever choice we make we stand by it unwaveringly, it's just normal to not want to hear that it may not have been the best choice. I don't think bdhilton is jealous, I think he sincerely wants to warn others who are just deciding. I believe he also posted a rather grim picture of surgery, which he had. I think he is scared, we all are (or should be), he just shows it more than others.

And it's not fair to suppress infomation for others who are just entering this world. So, bdhilton, keep up the good work, we come here to learn.

All that being said, I had HIFU, and I stand the same as all of you thinking that I made the right choice. I hope we all did, but it takes time to find out, we are all chained to the blood draw for a lifetime for a reason.

Choices
Amen, brother Buzzz. I appreciate every post and everyone on this site. Obviously I wished that everything I read pointed in the same direction and provided conclusive evidence that I made the best and right decision. HA HA!

I know that the choice I made (surgery) was right for me and I am sticking to it (what other choice do I have, it is done). I will probably always wonder what if... what if I did AS for another year or two or 8? What if I chose a less invasive proceedure? How would I feel if I waited too long or had a recurrence? Would I change my perspective?

I have a hard time advising anyone as to what is "best". I think that what is best for anyone is what they decide upon after prayer, professional advice and counsel, support from their network fo friends and family and then ultimately after judging their comfort level with the benefits and consequences of their choice.

As I said in another post, I had confusing and conflicting advice all the way up to the day before my scheduled proceedure. I was told, early on in the decision process, to make a decision and stick to it. I didn't know what that Dr. (not a urologist) meant at that time, however, I figured it out as time went on.

Good luck to everyone in recovery or in the process of deciding what to do and when to do it.

Charlie

Beau2

CharlieG said:

Choices
Amen, brother Buzzz. I appreciate every post and everyone on this site. Obviously I wished that everything I read pointed in the same direction and provided conclusive evidence that I made the best and right decision. HA HA!

I know that the choice I made (surgery) was right for me and I am sticking to it (what other choice do I have, it is done). I will probably always wonder what if... what if I did AS for another year or two or 8? What if I chose a less invasive proceedure? How would I feel if I waited too long or had a recurrence? Would I change my perspective?

I have a hard time advising anyone as to what is "best". I think that what is best for anyone is what they decide upon after prayer, professional advice and counsel, support from their network fo friends and family and then ultimately after judging their comfort level with the benefits and consequences of their choice.

As I said in another post, I had confusing and conflicting advice all the way up to the day before my scheduled proceedure. I was told, early on in the decision process, to make a decision and stick to it. I didn't know what that Dr. (not a urologist) meant at that time, however, I figured it out as time went on.

Good luck to everyone in recovery or in the process of deciding what to do and when to do it.

Charlie

Well Said
Buzzz and CharlieG,

I think your posts are right on. Thanks.

Kongo

buzzz said:

is cyber knife the best choice?
I'll probably get my head chopped off, but I checked into cyber knife. I was told that the group who invented this took radiation and made a new machine that is given in lesser dosage, and because of that you have less chance of side effects but more of a chance of recurrance. And, I was told that if you have side effects they come much later after treatment. I know of one recurrance, I don't know him personally, I just know of him.

It seems that whatever choice we make we stand by it unwaveringly, it's just normal to not want to hear that it may not have been the best choice. I don't think bdhilton is jealous, I think he sincerely wants to warn others who are just deciding. I believe he also posted a rather grim picture of surgery, which he had. I think he is scared, we all are (or should be), he just shows it more than others.

And it's not fair to suppress infomation for others who are just entering this world. So, bdhilton, keep up the good work, we come here to learn.

All that being said, I had HIFU, and I stand the same as all of you thinking that I made the right choice. I hope we all did, but it takes time to find out, we are all chained to the blood draw for a lifetime for a reason.

Fair enough
buzzz,

I appreciate your viewpoint and I for one wouldn't chop your head off. We all have to deal with much conflicting information as we make our choices and believe in them afterward. My beef with the author of this thread is that he has cherry picked several outdated news stories and mixed them together to deliberately create a negatively biased picture of a treatment option he personally feels is experimental.

I wish you would start a thread about HIFU and how your research led you pick it over other options. Many here would benefit from your experience as not many men (at least who have posted here) have sought a treatment overseas.

And BTW, while I have no idea who you consulted with about CyberKnife, I think you may have been misinformed. The dosage with CK is not a low dose. In fact it is quite the opposite. It wasn't until SBRT was developed that they could deliver a hypofractionated dosage that results in a BED in the mid-90 Gy range. And regarding recurrence, you are correct that there have been a few cases (out of about 5,000 treated to date) where PCa has returned as evidenced by a rising PSA after nadir. From what I have read these patients were in the higher risk categories of PCa. Recent studies involving fairly sizeable cohorts have had zero failures for the low risk cancer group. And you are right about side effects occuring much later and that is always a risk. For low risk cancer patients, however, the statistics are very favorable to date. Time will tell. The link I referenced in an earlier post on this thread gives the data I am referring to in this paragraph.

I hope your recovery continues to be positive.

hopeful and optimistic

cyberknife
Some questions'

Hiw long has cyberknife been around for prostate cancer: that is how long has there been documentation on the effects of cyberknife?....Also , knowing that we are amateurs (sp) do any of us have an idea on how long a study needs to be in order to measure the effectiveness of the treatment ?

When was cyberknife developed to treat other cancer types....how long has it been for each type, and what has been the successess or failures.

At a lecture that I attended, a doctor who specializes in braky was critical of other treatment types, and one of his mentions about cyberknife was that there is large investment in the technology , and prostate cancer treatment was developed to support the technology investment...how true is this.

Thanks

Kongo

hopeful and optimistic said:

cyberknife
Some questions'

Hiw long has cyberknife been around for prostate cancer: that is how long has there been documentation on the effects of cyberknife?....Also , knowing that we are amateurs (sp) do any of us have an idea on how long a study needs to be in order to measure the effectiveness of the treatment ?

When was cyberknife developed to treat other cancer types....how long has it been for each type, and what has been the successess or failures.

At a lecture that I attended, a doctor who specializes in braky was critical of other treatment types, and one of his mentions about cyberknife was that there is large investment in the technology , and prostate cancer treatment was developed to support the technology investment...how true is this.

Thanks

Ira,

In response to your question I’ve attempted to put together a brief history of CyberKnife drawn from my research into this treatment several months ago. I also referred to the website of Accuray, the present manufacturer, to refresh my memory on the dates I refer to. I also draw upon two papers published in the “Technology in Cancer Research and Treatment” journal. The first is a paper by Dr. Alan Katz who summarizes many of the studies that have been completed to date as well as his own experience. The second paper is a detailed technical description of the CyberKnife system published by Accuray in the same journal.

http://www.tcrt.org///mc_images/category/4309/04-katz_tcrt_9_5.pdf
http://www.tcrt.org//mc_images/category/4309/02-kilby_tcrt_9_5.pdf

CyberKnife was developed by a team of researchers at Stanford University led by Professor John Adler in the late 1980s as a frameless alternative to stereotactic radiation systems that used a linear accelerator (LINAC) that was in use at the time such as Gamma Knife. Gamma Knife delivers very accurate radiation does to brain tumors but requires the head to be bolted to a frame to hold it in place. What Adler and his team did was to basically move the LINAC from the frame to a highly maneuverable robotic arm that could move about the body and did not require rigid placement of the skull. Later developments integrated real time tracking systems that enable treatment of cancers in organs that move such as the lung. The FDA approved CyberKnife for treatment of brain tumors in 1999 and for treatment of tumors throughout the body in 2001. The prostate has been treated with CyberKnife since 2004 after fiducial tracking systems were developed in 2003 that allowed for real time tracking of prostate movement and software to enable the system to compensate dynamically, thus minimizing radiation to surrounding tissue and organs.

Interestingly, there is no controversy in the use of SBRT to treat head and neck cancers, lung cancer, pancreatic cancer, spinal cancer, or liver cancer. There is controversy within ASTRO on the use of SBRT to treat prostate cancer. I am unaware of the technical arguments within the ASTRO elite and have read various web discourse about internal politics but I don't know the details. It does seems inconsistent to me that they acclaim the use of CyberKnife for treatment of other body cancers without long term studies while at the same time saying that CK for prostate needs more study. Since 2008 (When ASTRO failed to give CK a strong endorsement for PCa as it did for other cancers) several studies have been published that show the continuing efficacy of CyberKnife and more are soon to be published.

In any event, like all radiation CK damages the DNA in cancer cells causing them to die when they try to divide, a process known as apoptosis. A characteristic that determines how sensitive a given type of cancer is to different types of radiation is known as the alpha/beta ratio. Since prostate cancer cells are so slow growing, they have a low proportion of dividing cells at any given time (the alpha beta ratio) which means they are very susceptible hypofractionated dosages delivered by SBRT systems.

A brief summary of how CK works at the radiobiological level is quoted from the Katz paper referenced above: “If the α/β ratio is high (e.g., around 10 Gy) there is little sensitivity to dose per fraction, as is the case in early responding normal tissues (such as mucosa and skin) and most tumors. A low α/β ratio, less than 5 Gy, would mean greater sensitivity to dose per fraction, as seen in late responding tissues. Since most tumors are not sensitive to fraction size but normal tissues are, many small doses of frac¬tionated radiotherapy optimizes tumor control and minimizes risk of late normal tissue damage. Studies have suggested that the α/β ratio for prostate cancer is as low as 1.2 Gy, putting it below the ratio of around 3-5 Gy for late responding tis¬sues. This would imply that a hypofractionated schedule of radiotherapy (i.e., fewer fractions delivered with a larger dose) would increase the therapeutic ratio by driving up the biological equivalent dose for tumor control and decreasing the equivalent dose for late tissue response.”

In using radiation to treat cancer, the goal is to deliver the highest amount of radiation that can cause the last amount of toxicity so that the treatment can significantly exceed the alpha/beta ratio and deliver a biological equivalent dose well above about 60 Gy which is a generally accepted threshold to kill cancer. In my case, for example, I received 5 fractions of 7.25 Gy that resulted in a BED of 96 Gy. The hypofractioned schedule of CK results in fewer incidences of side effects (late tissue response) which has been borne out by the studies highlighted in the Katz paper where he describes in much detail the efficacy of the treatment, particularly for low risk cancer patients. According to ASTRO, CK is a preferred method for treating the other types of cancer I mentioned above.

I have no idea what length of time qualifies as a “study.” Obviously the longer the better but I think at some point you have to begin believing trends in data when you make decisions, which is what I did. If you wait 10, 15, or 20 years to absolutely have long term data, some other technology will have surpassed what you started studying in the first place.

Suggest that you read the papers I listed for more detail.

Best

hopeful and optimistic

Kongo said:

Ira,

In response to your question I’ve attempted to put together a brief history of CyberKnife drawn from my research into this treatment several months ago. I also referred to the website of Accuray, the present manufacturer, to refresh my memory on the dates I refer to. I also draw upon two papers published in the “Technology in Cancer Research and Treatment” journal. The first is a paper by Dr. Alan Katz who summarizes many of the studies that have been completed to date as well as his own experience. The second paper is a detailed technical description of the CyberKnife system published by Accuray in the same journal.

http://www.tcrt.org///mc_images/category/4309/04-katz_tcrt_9_5.pdf
http://www.tcrt.org//mc_images/category/4309/02-kilby_tcrt_9_5.pdf

CyberKnife was developed by a team of researchers at Stanford University led by Professor John Adler in the late 1980s as a frameless alternative to stereotactic radiation systems that used a linear accelerator (LINAC) that was in use at the time such as Gamma Knife. Gamma Knife delivers very accurate radiation does to brain tumors but requires the head to be bolted to a frame to hold it in place. What Adler and his team did was to basically move the LINAC from the frame to a highly maneuverable robotic arm that could move about the body and did not require rigid placement of the skull. Later developments integrated real time tracking systems that enable treatment of cancers in organs that move such as the lung. The FDA approved CyberKnife for treatment of brain tumors in 1999 and for treatment of tumors throughout the body in 2001. The prostate has been treated with CyberKnife since 2004 after fiducial tracking systems were developed in 2003 that allowed for real time tracking of prostate movement and software to enable the system to compensate dynamically, thus minimizing radiation to surrounding tissue and organs.

Interestingly, there is no controversy in the use of SBRT to treat head and neck cancers, lung cancer, pancreatic cancer, spinal cancer, or liver cancer. There is controversy within ASTRO on the use of SBRT to treat prostate cancer. I am unaware of the technical arguments within the ASTRO elite and have read various web discourse about internal politics but I don't know the details. It does seems inconsistent to me that they acclaim the use of CyberKnife for treatment of other body cancers without long term studies while at the same time saying that CK for prostate needs more study. Since 2008 (When ASTRO failed to give CK a strong endorsement for PCa as it did for other cancers) several studies have been published that show the continuing efficacy of CyberKnife and more are soon to be published.

In any event, like all radiation CK damages the DNA in cancer cells causing them to die when they try to divide, a process known as apoptosis. A characteristic that determines how sensitive a given type of cancer is to different types of radiation is known as the alpha/beta ratio. Since prostate cancer cells are so slow growing, they have a low proportion of dividing cells at any given time (the alpha beta ratio) which means they are very susceptible hypofractionated dosages delivered by SBRT systems.

A brief summary of how CK works at the radiobiological level is quoted from the Katz paper referenced above: “If the α/β ratio is high (e.g., around 10 Gy) there is little sensitivity to dose per fraction, as is the case in early responding normal tissues (such as mucosa and skin) and most tumors. A low α/β ratio, less than 5 Gy, would mean greater sensitivity to dose per fraction, as seen in late responding tissues. Since most tumors are not sensitive to fraction size but normal tissues are, many small doses of frac¬tionated radiotherapy optimizes tumor control and minimizes risk of late normal tissue damage. Studies have suggested that the α/β ratio for prostate cancer is as low as 1.2 Gy, putting it below the ratio of around 3-5 Gy for late responding tis¬sues. This would imply that a hypofractionated schedule of radiotherapy (i.e., fewer fractions delivered with a larger dose) would increase the therapeutic ratio by driving up the biological equivalent dose for tumor control and decreasing the equivalent dose for late tissue response.”

In using radiation to treat cancer, the goal is to deliver the highest amount of radiation that can cause the last amount of toxicity so that the treatment can significantly exceed the alpha/beta ratio and deliver a biological equivalent dose well above about 60 Gy which is a generally accepted threshold to kill cancer. In my case, for example, I received 5 fractions of 7.25 Gy that resulted in a BED of 96 Gy. The hypofractioned schedule of CK results in fewer incidences of side effects (late tissue response) which has been borne out by the studies highlighted in the Katz paper where he describes in much detail the efficacy of the treatment, particularly for low risk cancer patients. According to ASTRO, CK is a preferred method for treating the other types of cancer I mentioned above.

I have no idea what length of time qualifies as a “study.” Obviously the longer the better but I think at some point you have to begin believing trends in data when you make decisions, which is what I did. If you wait 10, 15, or 20 years to absolutely have long term data, some other technology will have surpassed what you started studying in the first place.

Suggest that you read the papers I listed for more detail.

Best

Thanks for the very complete answer
I will read the papers

Thanks again,

Ira

Swingshiftworker

Kongo said:

Ira,

In response to your question I’ve attempted to put together a brief history of CyberKnife drawn from my research into this treatment several months ago. I also referred to the website of Accuray, the present manufacturer, to refresh my memory on the dates I refer to. I also draw upon two papers published in the “Technology in Cancer Research and Treatment” journal. The first is a paper by Dr. Alan Katz who summarizes many of the studies that have been completed to date as well as his own experience. The second paper is a detailed technical description of the CyberKnife system published by Accuray in the same journal.

http://www.tcrt.org///mc_images/category/4309/04-katz_tcrt_9_5.pdf
http://www.tcrt.org//mc_images/category/4309/02-kilby_tcrt_9_5.pdf

CyberKnife was developed by a team of researchers at Stanford University led by Professor John Adler in the late 1980s as a frameless alternative to stereotactic radiation systems that used a linear accelerator (LINAC) that was in use at the time such as Gamma Knife. Gamma Knife delivers very accurate radiation does to brain tumors but requires the head to be bolted to a frame to hold it in place. What Adler and his team did was to basically move the LINAC from the frame to a highly maneuverable robotic arm that could move about the body and did not require rigid placement of the skull. Later developments integrated real time tracking systems that enable treatment of cancers in organs that move such as the lung. The FDA approved CyberKnife for treatment of brain tumors in 1999 and for treatment of tumors throughout the body in 2001. The prostate has been treated with CyberKnife since 2004 after fiducial tracking systems were developed in 2003 that allowed for real time tracking of prostate movement and software to enable the system to compensate dynamically, thus minimizing radiation to surrounding tissue and organs.

Interestingly, there is no controversy in the use of SBRT to treat head and neck cancers, lung cancer, pancreatic cancer, spinal cancer, or liver cancer. There is controversy within ASTRO on the use of SBRT to treat prostate cancer. I am unaware of the technical arguments within the ASTRO elite and have read various web discourse about internal politics but I don't know the details. It does seems inconsistent to me that they acclaim the use of CyberKnife for treatment of other body cancers without long term studies while at the same time saying that CK for prostate needs more study. Since 2008 (When ASTRO failed to give CK a strong endorsement for PCa as it did for other cancers) several studies have been published that show the continuing efficacy of CyberKnife and more are soon to be published.

In any event, like all radiation CK damages the DNA in cancer cells causing them to die when they try to divide, a process known as apoptosis. A characteristic that determines how sensitive a given type of cancer is to different types of radiation is known as the alpha/beta ratio. Since prostate cancer cells are so slow growing, they have a low proportion of dividing cells at any given time (the alpha beta ratio) which means they are very susceptible hypofractionated dosages delivered by SBRT systems.

A brief summary of how CK works at the radiobiological level is quoted from the Katz paper referenced above: “If the α/β ratio is high (e.g., around 10 Gy) there is little sensitivity to dose per fraction, as is the case in early responding normal tissues (such as mucosa and skin) and most tumors. A low α/β ratio, less than 5 Gy, would mean greater sensitivity to dose per fraction, as seen in late responding tissues. Since most tumors are not sensitive to fraction size but normal tissues are, many small doses of frac¬tionated radiotherapy optimizes tumor control and minimizes risk of late normal tissue damage. Studies have suggested that the α/β ratio for prostate cancer is as low as 1.2 Gy, putting it below the ratio of around 3-5 Gy for late responding tis¬sues. This would imply that a hypofractionated schedule of radiotherapy (i.e., fewer fractions delivered with a larger dose) would increase the therapeutic ratio by driving up the biological equivalent dose for tumor control and decreasing the equivalent dose for late tissue response.”

In using radiation to treat cancer, the goal is to deliver the highest amount of radiation that can cause the last amount of toxicity so that the treatment can significantly exceed the alpha/beta ratio and deliver a biological equivalent dose well above about 60 Gy which is a generally accepted threshold to kill cancer. In my case, for example, I received 5 fractions of 7.25 Gy that resulted in a BED of 96 Gy. The hypofractioned schedule of CK results in fewer incidences of side effects (late tissue response) which has been borne out by the studies highlighted in the Katz paper where he describes in much detail the efficacy of the treatment, particularly for low risk cancer patients. According to ASTRO, CK is a preferred method for treating the other types of cancer I mentioned above.

I have no idea what length of time qualifies as a “study.” Obviously the longer the better but I think at some point you have to begin believing trends in data when you make decisions, which is what I did. If you wait 10, 15, or 20 years to absolutely have long term data, some other technology will have surpassed what you started studying in the first place.

Suggest that you read the papers I listed for more detail.

Best

Great Summary!
Great summary of CK, Kongo!

The only thing I would add is that the current protocol for CK is designed to model the radiation dosage for HDR (high dose rate) brachytherapy. So, there really is no risk of getting a low or ineffective radiation dosage from treatment. The advantage of CK over HDR BT is that is more precisely delivered w/o all of the common side effects from BT, including incontinence and ED caused by the less controlled delivery of the radiation to the prostate (urethra and penile bulb) as well as to surrounding issue (rectum & bladder) from the seeds placed in the prostate.

You really should publish a brochure or start a blog to consolidate all of the info available on the topic. BTW, I'm having a great time in Mexico. Spent 3 days in Puerto Vallarta and am now on my 2nd day in Manzanillo (about 272 miles south of PV). Heading to Guadalajara (another 267 miles) day after tomorrow for 5 more days before returning to PV for 3 days more before I return to the good old USA.

Keep up the good work holding down the fort here. LOL!

mrspjd

Swingshiftworker said:

Great Summary!
Great summary of CK, Kongo!

The only thing I would add is that the current protocol for CK is designed to model the radiation dosage for HDR (high dose rate) brachytherapy. So, there really is no risk of getting a low or ineffective radiation dosage from treatment. The advantage of CK over HDR BT is that is more precisely delivered w/o all of the common side effects from BT, including incontinence and ED caused by the less controlled delivery of the radiation to the prostate (urethra and penile bulb) as well as to surrounding issue (rectum & bladder) from the seeds placed in the prostate.

You really should publish a brochure or start a blog to consolidate all of the info available on the topic. BTW, I'm having a great time in Mexico. Spent 3 days in Puerto Vallarta and am now on my 2nd day in Manzanillo (about 272 miles south of PV). Heading to Guadalajara (another 267 miles) day after tomorrow for 5 more days before returning to PV for 3 days more before I return to the good old USA.

Keep up the good work holding down the fort here. LOL!

HDR-Brachy vs Brachy: two very different PCa txs
Seems that a clarification needs to be made once again, between HDR-B and Brachy--two DIFFERENT radiation treatments for PCa that are often confused. There is a very big difference between HDR-Brachy (HDR-B is High Dose Rate radiation Brachy) which is a TEMPORARY high dose radiation delivery procedure vs the more common and well known procedure called Brachy (radioactive seeds) in which the radioactive seeds are PERMANENTLY implanted in the prostate. Usually, the permanent Brachy seed implants are a less precise delivery system with more potential for side effects, especially in later years. With HDR-Brachy, the procedure usually requires an overnight stay in the hospital, high dosing is delivered directly into the prostate in precise measured high dosing over a period of time (approx 24 hrs) from "the inside out" via temporary lines/wires. When the HDR-B procedure is completed, the "lines" are removed and other than the radiation that was delivered, there is nothing left in the prostate (no radioactive seeds, etc). HDR-B is not for everyone, but it's precise measured dosing directly into the prostate (similar to the high dosing used in external SBRT-stereotactic body radiation), and in the hands of a skilled and experienced md, may have less potential side effects than Brachy (seeds), and can be a highly effective and successful PCa tx, especially for intermediate risk PCa. Both HDR-Brachy as well as Brachy seeds can also be combined with IM/IGRT in a comprehensive PCa tx plan, most often for intermediate risk PCa.

Oh, and btw, HDR-B has been used in the successful treatment of PCa since the late 1980's AND clinical study data IS available for 10+ years.