Join Date: Nov 2007
Location: Annandale, VA, USA
Re: Brachytherapy vs. CyberKnife
Hi and welcome to the board! I'll insert some thoughts in green.
Originally Posted by prostate
I live in the California Bay Area. CyberKnife (CK), seems to be currently practiced widely in combination with a Stereotactic Body Radiotherapy (SBRT) dosing schedule. What that means is that the full radiation dosing is done on a much abbreviated schedule. The common CK-SBRT schedule, the only one that most of us have probably heard of, delivers the full dose in just five sessions. I'm mentioning this because the team with a strong claim as the #1 leader is right in your area at Stanford University. The leading researcher/physician is Dr. Christian (or Christopher) King, MD.
Does anyone know of any current (2< old) literature that discusses/compares these 2 treatment options? Unfortunately, the only research we have on CK-SBRT for prostate cancer is very current because that therapy has just not been around very long. In fact, that's the biggest knock on that therapy for prostate cancer at present, and even for the research that has been published, follow-up data is very short.
Dr. King's group has reported results with average follow-up of nearly three years, and their initial report of that data was well over a year ago. Hopefully, their update will continue their favorable findings through an average follow-up of five years, a really key time threshold in radiation therapy because some late breaking side effects can take that long to develop. Frankly, I was disappointed they did not update with more follow-up at the CK users group convention last February. Such omissions always make me wonder what is going on. Fortunately for patients just now considering CK-SBRT for prostate cancer, there should be another convention in February, and it seems very likely to me that the King group will give that awaited update. Hopefully other groups will also publish their results.
I'm a laymen with no enrolled medical education, but I've heard some respected radiation doctors talk about CK-SBRT, and they are concerned. They like the early results for CK SBRT, but they are uneasy with the big increase in dose delivered per session - up from around 2 Gray (over approximately 40 sessions these days for external beam therapy, to around 7 Gray delivered in just five sessions). It doesn't bother them that about half the usual external beam dose is delivered; their formulas tell them that the reduced dose should be about equivalent in potency, but they are concerned about side effects. For them, it's a really large jump from 2 gray to 7 gray without taking steps in between. Also, though they are pretty comfortable that CK SBRT is as potent, they would like to see some reasonably mature results, especially for side effects, particularly late emerging rectal side effects.
Of course, brachytherapy will deliver even higher doses than 80, but the big difference with EBRT and CK is that the radiation does not pass through other bone and soft tissue to reach the prostate, so you don't have the same side effect concern for those higher brachytherapy doses.
Or any that simply details success of each? Thanks. Again, CK SBRT is so young that you need a bit of gambler's spirit to go with it. Take Dr. King's series of 41 men (probably larger now). The first 20 went through five straight days of CK SBRT and they were done. However, the doctors began noticing an unexpected and rather high rate of severe late rectal complications. In fact the reported rate was 38% - far higher than for other forms of radiation. The King group doctors then decided to skip a day between each of the five sessions, and that dropped the late severe rectal side effect rate to zero! In one sense, that's problem solved! But in another sense, it shows that a major issue was being worked out in just the past few years. In my book, CK SBRT is simply not a mature therapy approach yet. That said, it may prove in time to be a wonderful advance.
You can look at research on brachytherapy and CK SBRT yourself. Go to www.pubmed.gov, a site we can use on this board because it is Government sponsored, and search for, say (without the quotation marks), " prostate cancer AND CyberKnife ". I just did that and got 17 hits. However, several of them did not have abstracts, as indicated by the "No abstract available" notation, which means their usefulness to us, lacking convenient access to the source journals, is greatly decreased. For those papers with abstracts, you view it for free by clicking on the blue hypertext title.
I used this string to check papers that might have some of the comparative features you wanted: " prostate cancer AND CyberKnife AND brachytherapy ". That resulted in three hits, all recent, but only two had abstracts.
In sharp contrast, a search for " prostate cancer AND brachytherapy " yielded 2,813 hits!
Good luck and happy searching,