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Trying to reduce my ignorance
JM
Posted: Sunday, March 01, 2009 5:49 PM
Joined: 2/23/2009
Posts: 5


Hello. I have read some of the threads here and found them very informative. I was recently (3 weeks ago) diagnosed with Prostate Cancer. My PSA was elevated for the first time. It was repeated and confirmed at 5.6. Had a digital rectal exam, which was negative for anything gross. Needle biopsy followed (experience can best be described as proctologist meets voodoo doctor with me as a cross between patient and voodoo doll). Pathology came back positive on 2 of 12 (I was originally told 1 of 12, asked for a second opinion by pathologist at Hopkins, Dr. who had done the needle biopsy called and apologized profusely that both pathologists reported 2 of 12). First pathologist's report (don’t have second yet) states for the 2 positive samples (Right Lateral Mid and Left Lateral Apex) "prostate tissue with minute focus of adenocarcinoma of the prostate, Gleason score 3+3. Comment: the diagnosis of carcinoma is supported by the failure of immunoperoxidase staining for high molecular weight cytokeratin and p63 to demonstrate basal cells in the atypical glands." Dr. who did needle biopsy is recommending daVinci robotic surgery, which is what he does. Having been told my case isn't terribly urgent, I am investigating all my options. This coming Tuesday I meet with a surgeon at Johns Hopkins who specializes in non-robotic (traditional) surgery and a couple weeks after that I meet with a team at Georgetown University Hospital to discuss their options which include CyberKnife. So, please help me prepare so I get the most I can out of these. In trying to understand external radiation treatments in general it seems that the goal is to deliver radiation to the bad tissue and spare the good tissue. So, is external radiation (CyberKnife or other) a Gaussian plane wave of small diameter or is it actually a focused beam that converges to a spot at some point in the body? Once the fiducial markers are inserted, how is the surface of the prostate mapped with respect to the fiducial marker locations? How do you know that the fiducial markers don’t move after insertion during the course of treatment (I have heard that brachytherapy seeds can, and sometimes do, move even to the point of entering the urine stream). Also, it seems that much of the discussion focuses of the pros and cons of CyberKnife versus surgery and CyberKnife versus other external beam radiation, but there isn’t as much discussion of CyberKnife versus brachytherapy. And, one last thing for now, surgeons say that once you have radiation and it fails, surgery isn’t an option. However, if surgery fails, radiation is always an option. Does failed surgery ever result in follow-up surgery or is radiation always the recourse? Thanks very much, Jeff.
viperfred
Posted: Sunday, March 01, 2009 11:10 PM
Joined: 10/10/2008
Posts: 788



Hi JM.

Great questions.


From a patient point if view it is important to understand all options and their benefits and risk.  It can be confusing but with a little research you will figure out what is best for you.

With radiation it helps to understand the dose impact on the chance of cure.  From my research high dose over a few sessions has a higher chance of cure than a lower dose for many sessions,

IMRT, 3D-RT Brachytherapy (permanent seeds are low dose) The CyberKnife and HDR Brachytherapy is high dose radiation or hypo fractionation.

I also met with a surgeon and radiation oncologist.  Surgery was not on my radar because of the immediate risk of ED and other side effects and at typically higher rates than radiation. Add the risk from general surgery, infection, blood loss and recovery time eliminated surgery quickly for me.

I had not heard of the CyberKnife when I met with Dr. King a radiation oncologist at Stanford.  I went to our first consultation with a binder of years of research including Proton Therapy and derivatives of IMRT and Brachytherapy.  He said I was a good candidate for IMRT and since I was looking at all options I might want to look at the CyberKnife.  Once I started to understand how the target tracking and real time beam adjustment impacted the treatment dose margin worked. It seemed like a great option as the data to data also was very encouraging.  It looks even better today with one more year under the belt.

I have learned there are no guarantees but the best chance for cure is with HDR by Brachytherapy or the CyberKnife.  I have the edge to the CyberKnife as I felt its prostate tracking would be equal or better than HDR Brachytherapy.  Risk of ED short term was small and long term not proven but expected to be no worse than any other option.  Other side effects were minimal and expected to be of short duration but until 10 years passes no one knows.

I am almost 10 months post CyberKnife and very happy with my choice. No ED. minimal side effects gone in two weeks and minor issues gone in three months.

Good luck with whatever you feel is best for you.

 


radsrus
Posted: Monday, March 02, 2009 3:08 AM
Joined: 10/10/2008
Posts: 4140


1. I haven't a clue what a Gaussian plane wave is, but radiation uses multiple beams to achieve concentration of the energy in a defined area. 3-D conformal uses about 4, IMRT 6-9, and CK 200 or more (for prostate cancer).  The higher the number of beams used the more concentrated the beam energy in the desired location.

2. CT and MRI are used to map the prostate in three-dimensional space. The fiducial markers can be seen at least on CT and sometimes on MRI.

3. The seeds may move a little after insertion, but after a week remain steady. We know this because we can track their locations very precisely.

4. Data to date suggests that CK very closely follows HDR brachytherapy in effects, which is not surprising since it was designed to accomplish HDR type treatment much less invasively. HDR is superior to seeds.

5. Surgery can be done after radiation and vice versa. Because of results, we get much less chance to perform surgery after radiation failure than to perform radiation after surgical failure. As I have said many times, it it irrational to spend much time worrying about what you might do as a salvage treatment when there is a 98% chance of success. Surgery with radiation afterwards (for positive margins, etc.) is about as good as HDR or CK alone.



 

Clinton A. Medbery, III, M.D.
St. Anthony Hospital Cyberknife Center
(405) 272-7311
buddy@swrads.org

Mail to:
Clinton A. Medbery, III, M.D.
Southwest Radiation Oncology
1011 N. Dewey Ave. #101
Oklahoma City, OK 73102

 


JM
Posted: Monday, March 02, 2009 6:37 AM
Joined: 2/23/2009
Posts: 5


fred/viperfred, thanks for your thoughts, at this point I am trying to be as open-minded as possible to all approaches. Frankly, every option is a little bit scary. I guess it is somewhat made worse by the fact that there are so many options, all of which have their pros and cons and, yet, ultimately have a good chance of a cure. I suppose that should make me feel fortunate but it is also overwhelming. Thank goodness I have a little time to decide. Again, thanks.
JM
Posted: Monday, March 02, 2009 6:56 AM
Joined: 2/23/2009
Posts: 5


Dr. Medberry, thanks for your information. Perhaps a better term than a Gaussian plane wave is to ask if the beam is collimated? In other words, does the beam diameter stay constant as it travels through space? A Gaussian plane wave is a beam where the strength of the beam transverse to the direction of propagation is a Gaussian function that is the same anywhere along the beam. I am probably mixing terminology from much much lower frequencies and that is causing confusion. So, what I am trying to understand is: are the radiation beams in a CyberKnife (or any external radiation system) staying the same diameter on the target (prostate) as when they leave the source, or are they diverging, or are they converging on the prostate? Maybe I shouldn't be thinking about it on this level, but it does have implications for the amount of energy that is delivered to good versus bad tissue. Irrespective of the answer, it makes sense that more beams would be better in that, in principle, the surrounding tissue would, in best case see only 1/N of the radiation (where N is the # of beams). From the numbers you gave, I would infer that the dosage to good tissue using CyberKnife would be 20 or more times less than other external techniques. Again, thanks very much, Jeff.
Dr. J
Posted: Monday, March 02, 2009 8:00 AM
Joined: 10/11/2008
Posts: 1070


The beams converge toward the prostate, but each individual beam is actually diverging as it leaves the collimator.  It all comes down to semantics, but a larger number of beams is more sparing of normal tissue although the Integral Dose to the patient as a whole may be higher (integral dose is the sum of all dose received by all tissue and is volume dependent.  More beams mean more normal tissue receiving a low dose rather than a fewer areas receiving a higher dose).

 

Jerome J. Spunberg, M.D., FACR, FACRO
CyberKnife Center of Palm Beach
jspunberg@radiationoncologyinstitute.com
(561) 799-2828

 

Radiation Oncology Institute
10335 N. Military Trail, Suite C
Palm Beach Gardens, FL 33410
(561) 624-1717


Dr. J
Posted: Monday, March 02, 2009 8:00 AM
Joined: 10/11/2008
Posts: 1070


P.S.  I was a physics major when I entered college.

 

Jerome J. Spunberg, M.D., FACR, FACRO
CyberKnife Center of Palm Beach
jspunberg@radiationoncologyinstitute.com
(561) 799-2828

 

Radiation Oncology Institute
10335 N. Military Trail, Suite C
Palm Beach Gardens, FL 33410
(561) 624-1717


radsrus
Posted: Monday, March 02, 2009 8:10 AM
Joined: 10/10/2008
Posts: 4140


My knowledge of physics is almost certainly less than that of Dr. Spunberg, but I am unaware of any beam that does not diverge as it moves through space. But Dr. Spunberg's explanation is correct and they way to think about this.


 

Clinton A. Medbery, III, M.D.
St. Anthony Hospital Cyberknife Center
(405) 272-7311
buddy@swrads.org

Mail to:
Clinton A. Medbery, III, M.D.
Southwest Radiation Oncology
1011 N. Dewey Ave. #101
Oklahoma City, OK 73102

 


JM
Posted: Monday, March 02, 2009 10:49 AM
Joined: 2/23/2009
Posts: 5


Drs. Medbery and Spunberg, thanks, that is what I suspected the answer was going to be but it is nice to know. As to beams being convergent, lots of lens systems accomplish this (think of frying bugs with a magnifying glass when you were a little kid). As long as the beam diameter is small enough at the target, it probably doesn't matter. In fact, maybe it is better if it isn't because the density might be too great at the focal point. What is the approximate beam diameter at the prostate? Sorry to be a nuisance, but the more I can understand about how the treatment is working the better I can feel about making the best choice for me. Also, when choosing a center to treat prostate cancer with CyberKnife, how many prostate cancer cases should they have treated before you would consider them to have "climbed the learning curve"? While I am sure there is very specialized training everyone undergoes, real world experience is important too. Thanks, Jeff.
radsrus
Posted: Monday, March 02, 2009 11:26 AM
Joined: 10/10/2008
Posts: 4140


With a magnifying glass you use lenses to bend light to focus it. THere are no lenses for radiation therapy of any kind. There is no density since photons have no mass.

THe beam diameter for prostate treatment with the CK can be anywhere from 5-60 mm, but generally is in the 15-40 mm range (at the target).  With more standard radiation, the field size is whatever is needed to cover the target.

I don't think there is a magic number to define experience. Being treated on in investigational protocol provides some extra insurance since the first few plans done by a center are reviewed by a very experienced center.


 

Clinton A. Medbery, III, M.D.
St. Anthony Hospital Cyberknife Center
(405) 272-7311
buddy@swrads.org

Mail to:
Clinton A. Medbery, III, M.D.
Southwest Radiation Oncology
1011 N. Dewey Ave. #101
Oklahoma City, OK 73102

 


JM
Posted: Monday, March 02, 2009 5:19 PM
Joined: 2/23/2009
Posts: 5


Thanks Dr. Medbery. It seems that the beam diameter is small enough to accurately target different parts of the prostate which, if I understand it, is all that is really required. Visible light and x-rays are both photons, just a lot different in wavelength. I was using the magnifying glass as an example of a converging beam. While refractive optics don't really exist at x-ray frequencies there are other x-ray optic techniques (like grazing incidence mirrors) that allow these frequencies to be focused. These discussions are helping me to appreciate the CyberKnife technology and it makes a lot of sense to me why it is preferable to other external radiation techniques. Again, thanks, Jeff.
radsrus
Posted: Monday, March 02, 2009 6:30 PM
Joined: 10/10/2008
Posts: 4140


As long as they don't graze off the cliff...

 

Clinton A. Medbery, III, M.D.
St. Anthony Hospital Cyberknife Center
(405) 272-7311
buddy@swrads.org

Mail to:
Clinton A. Medbery, III, M.D.
Southwest Radiation Oncology
1011 N. Dewey Ave. #101
Oklahoma City, OK 73102

 


 

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