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Posted 9/28/2009 9:51 PM (GMT 0)
After reading lots of posts concerning salvage radiation after surgery, I have a question.

If the best time to radiate is before the 0.5 PSA level, then that would mean very small, even microscopic levels of cancer.  At that size, it is impossible to know exactly where these rogue cells are at, only that they are somewhere in the prostate bed if still local. 

Now the idea is to radiate these cells, which I guess this will do something to them to cause them to die.  Not exactly sure how (alter cell DNA?).   But what about all the other normal healthy cells in the immediate area.  They are going to receive the same amount of radiation and thus will have the same death as the cancer cells.

Now don't get me wrong, but if you can't find the micrscopic cancer cells to aim at, how are you going to prevent damage to healthy cells?  Isn't it a little bit like trying to hit one duck in a flock of geese using a shot gun?  You may or may not hit the duck but you're gonna kill alot of geese in the process.

Can those that have more knowledge on this shed some light?

Posted 9/28/2009 10:46 PM (GMT 0)
Les, very good questions, and concerns a bunch of us right now, myself included.

I am learning as I go down the SRT route, first zap is still this coming Monday, waiting to be told the final number of treatments and gys.

What my radiation oncologist explained to me, was that she was studying my surgical notes in great detail, and took so many CAT scans, that she wants to see me slice by slice. She is going to try to model the zaps in a somewhat 3-D manner, to line up the heaviest of the does going to where she believes my one margin was. This is why there has been a 2 week wait since I was mapped and tattooed. She wanted a chance to take it all in account. She is also compensating for the fact that I have continual blockage issues due to difficulties at the bladder neck and excessive scarring. So she's trying to protect me from further harm there, thus one reason why I will be having the suprapubic cath installed this Thursday. I will be wearing it for the duration of the SRT, so at least 2 months, possible a 3rd to allow some of the swelling to go down after the SRT ends.

No, they don't know exactly where the cells are, how many there are. The 2nd rad. oncologist I met with, quantified my remaining cancer this way, based on prostate size and tumorsize, he said my post surgery psa of .16 at the time equated to 1/1000th of the previous cancer. But finding it is the hard part, and that's assuming its not already long gone from the prostate bed and/or pelvis area, i.e. through nerves.

Contrary to Dr. Walsh's great book in particular, all 3 rad. oncologists I met with said that perreniual invasion is an important clue, because those nerves are open ducts to the world outside your prostate, an easy path for stray cancer cells to roam freely.

Hope this helps, if I learn more in the days ahead, will pass it on.

David in SC
Posted 9/28/2009 10:55 PM (GMT 0)
I think the key factor is that cancer cells grow more quickly, so divide more often. That is the time cells are most susceptible to radiation. So the mortality rate for cancer cells should be higher than for nearby healthy cells.

Even if you hit your duck, you will still knock out a few geese, but let's hope they were geese you didn't really need :-)
Posted 9/29/2009 12:03 AM (GMT 0)
Piano,

That is always a risk with any kind of RT, sometimes the good goes with the bad. I still suffer ill effects 10 years after having RT for a rare cancer in the throat. It did a number on my saliva glands, could'nt spit 5 feet if I had too. At the time of the treatments, did a lot of short term damage to my ears ,voice box, taste buds, etc. So RT is always a trade off in my book, not like they can isolate it to the bad cancer cells only.

David in SC
Posted 9/29/2009 1:38 AM (GMT 0)
Les,
The theory of radiation, proton, Xray, or photon is the same. Particles are accelerated and hit individual cells and destroy their DNA. Fortunately cancer cells are much more suseptable to this than normal cells. Normal cells are also killed, but at a much lower rate; this is why the application of the correct dose to the correct area is essential. A damaged normal cell will repair itself over time, whereas a damaged cancer cell will always die. The trick in radiation has always been to get the exact dose nessary to kill all the cancer cells, but not high enough to kill the good cells surrrounding it. Over the years they have been able to increase the standard dose from 65g to about 81g because of the increased accurracy of the newer machines in their ability to spare surrounding good tissue.
JT
Posted 9/29/2009 2:17 AM (GMT 0)
I would like to know what dose I had 10 years ago, was done at the same center I will be starting at on Monday. Curious of the method and the gys used. In those days, it would have never occured to me to ask questions. After 5 surgeries related to the cancer, I was tired of the whole thing by the time I had to have radiation. Believe it was spread over 35 days.
Posted 9/29/2009 12:53 PM (GMT 0)
Thanks JohnT, David and Piano for your replies. I still having a little trouble understanding, that even with the more "accuracy" of the newer machines etc...that would lead me to believe that the doctor has a pretty good idea where to aim. However, if they base where to aim the machine on where they "think" it is located, then there is still the possibility that they could be wrong and alot of healthy cells are going to be radiated and possibly miss the cancer cells completely.

So then, how do the doctors figure out where to aim the dang machine. In the case of David and myself, a positive margin would be a very big clue. But what about those that had no margins? Who makes the decision where to aim, the radiation oncologist, the surgeon, the urologist? Is this the reason why SRT success rates are only around 50%? The decision for SRT, is a little bit more difficult than the decision for surgery in the first place.
Posted 9/29/2009 1:22 PM (GMT 0)
Les, that's the same fight in my mind/heart I have had ever since it was determined that I had re-accurance barely 6 months after surgery. With a known positive margin, at least there is a chance of trying to "reconstruct" things to calculate a more exact aiming place for the bulk of the radiation. Without anything to go by, its a shot in the dark in my opinion.

Yes, it still bothers me that the success rate for SRT is generally around 50%. If you have other risk factors, including strong PSA velocity like I do, then it drops to the 30-40% range.

From what I gathered first hand, the radiation oncologist makes the final call about where and how much. In my case, she has consulted several times with my uro/surgeon, in particular the location of the positive margin, and details on the complications at my bladder neck.

The final mapping will be determined from what she puts together from all the information.

I will start Monday, my body will show up at the clinic in a mechanical sense, by after all these weeks, my mind and heart doesn't agree. But at 57 years old, I have no choice but to take my chances that I will be in the 30-40% group with my stats that it will do some good. Not in denial at all, if anything, the opposite, almost a fatalistic attitude. If this doesn't work, seems like a lot of hassle, troubles, pains, and money down the drain. Hard for me to put a good spin on it.

On the positive side, I am thankful that my sequence of treatment beginning with surgery, allows for a substantial second chance so to speak. For those that keep discounting the notion of Surgery first, Radiation second, somehow miss the uniqueness of that opportunity. I don't hear them speaking of their salvage plans if needed.

Finally, some act like if there is a positive margin, or other spread, it means the surgeon did a poor job. The cancer cells don't light up, there is no dotted line to cut along. A good experienced surgeon does the best he/she can with each patient. They are having to consider a lot of margins, a lot of factors, etc. I for one, don't blame my surgeon for my situation. It's the aggressive of my cancer that is keeping it alive and well and unfortunately, on the move as we speak. Some act like all PC cells are slow moving and it can take forever to form into anything, my own dr and the 3 rad. oncologists I spoke to find that an odd view to take, considering the multiplying rate of the more agressive cancers.

SRT isn't pleasant to think about or dwell upon, like I have done for weeks, but the alternative to not doing it at a younger age makes less sense.

David in SC
Posted 9/29/2009 4:49 PM (GMT 0)
Les,
They take a CT scan of the area; this identifes the prostate and prostate bed. Then the scan is sent to a phyisist who develops a dose plan. The plan is sent back to the radiologist and input. The plan can follow the contour of the bed to whatever margin is set. It can also avoid or give a lower dose to the bladder neck and other areas. If a tumor is identified they can target the individual tumor or lymphnode. If they can't identify one, the suspected area is radiated. For suspected lymphnode the entire pelvic area is steralized.
IMRT rotates around you and puts out thousands of beams from all directions all coming together at an exact point. That point gets all the radation energy, and because it is comming from thousands of different directions the normal tissues it goes through only get a mere fraction of the total energy.
It is like focusing a thousand magnifying glasses on one point; no one beam would have the energy to light a fire, but when all beams hit that one point a great amount of heat is generated at that point.
The reason that SRT has a poor success rate is that agressive PC, G8 and above have a greater chance of getting into the bloodstream and causiing micomets. Billions of pc cells roaming through your body looking for a place to set up, which is usually the lymphnodes. Once the pc escapes the prostate bed and gets into the blood stream SRT is of no use. SRT will kill all the PC cells that are localized in the prostate area, but if cells are already in the bloodstream or lymphatic system only HT can stop them from growing.
JT
JohnT
Posted 9/29/2009 6:19 PM (GMT 0)
Good explanation JohnT...thank you. It is hard to visualize all those rays coming to an exact point where the cancer is suspected to be. If the cancer wasn't there, then other tissue is going to suffer. If it happens to be the nerves...they don't grow back. If it is the urethra...then burning for awhile when urinating. If its the rectum or colon...well another member had that happen and is still suffering the effects today. With bladder filling the void where the prostate used to be, this is tricky stuff.

Not trying to be negative here, as there are a good number of successful SRT guys here. I was just curious in how SRT is performed and what makes for a considered successful treatment and how the side effects are being reduced. It sure seems like a person is going to need a very good radiation oncologist to map out a game plan. It's not a simple point and shoot with a ray gun, that's for sure.

Again thanks JohnT...your shared knowledge (and others) is greatly appreciated.
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