There is a lot of misconceptions in many of the above posts about
CK.
CK is not a targeted therapy - it covers the entire prostate when used as a monotherapy- that's a fact. I'm not sure if that's true when used as a "boost" after tradition radiation (IMRT).
In general there are two treatment plans - homogeneous & heterogeneous , although the homogeneous plan also delivers a slightly higher dose to some portions of the prostate, according to my R.O.
The heterogeneous plan can give a HDR like dose and Dr. Katz's studies have shown a better result than HDR. And he also uses CK as monotherapy for high-risk disease, although not all CK Centers do.
One of the BIG advantages of CK is that it utilizes a a hypofraction dose delivery - fewer doses, but each is much higher than traditional radiation therapy. Because of the low alpha/beta ratio of CaP, this results in a much higher biomedical equivalent dose (BED). So a dose of 36.25 Gy ( 5 x 7.25 Gy ) results in a BED of over 80 Gy. And a HDR plan ( 40 Gy to certain parts of the prostate) gives a BED of over 100 Gy.
Because a lower dose is delivered to good tissue ( that has a much higher alpha/beta ratio ) , less toxicity results. And because the LINAC ( source of radiation ) is mounted on a robotic arm that takes on many position during treatment, the radiation is spread out in the good tissue and the dose is much reduced to the good tissue, and the radiation can be delivered to any portion of the prostate.
The CK machine can deliver radiation to better than a 1mm accuracy - about
1/3 that of tradition radiation. This results in less "spill-over" to good tissue - like the rectum, urethra, and AV bundle, even though a higher dose is given per treatment. This results is less side effects / toxicity.
It isn't more expensive than other treatments. Dr. Katz will do the entire procedure ( plus the cost of an MRI ) for $18K. AND, that's just the treatment cost. To compare each treatment, the overall cost should be considered - that would include treatment for complications, too. Since there are fewer complications with CK, that would reduce the overall cost compared to other treatments.
Frankly, for low and medium risk CAP, I think more patients should opt for CK. Dr. Katz claims his patients have better results than surgery or brachytherapy. He has treated over 600 patients. It is getting more popular and more machines are being installed. The machine can be used for treating other cancers and conditions, also. With the robotic arm, it is very versatile. I think CK scares the heck out of many urologists and R.O.'s that do standard radiation - it is a real threat to their business.
CK is basically the next generation of radiation therapy, as I see it. There are other machines that can do hypofractionization, but the CK machine is the only machine that has the LINAC mounted on a robotic arm. RapidArc uses a circular gantry. Dr. Chris King, one of the leading R.O.'s that used to do RapidArc at Stanford is now at UCLA and uses CK. Not sure why he made the switch, to be honest, but I wouldn't think he would take a step "backward".
And, IMH(non-medical)O , external radiation hits the periphery of the prostate first, not last, as with brachytherapy. SInce most tumors are in the periphery, this (to me) seems like an advantage as far as effectiveness goes. And Dr. Katz claims better results with a CK HDR plan compared to BT, so maybe this is why (?).
See Dr. Katz's website for more detailed information, including the results of a pooled study of 1,100 patients that were CK treated :
http://www.cyberknifeprostateradiosurgery.com/ , or the Accuray website for more detailed info. about CK.
BTW, the first U.S. patient to be treated with CK was a neurosurgeon in 2003. The last report is that he is doing just fine. The CK machine has been FDA approved since 2001, the same year the first patient in Korea was treated for CaP with CK.