Amount of radiation with SRT

You all may recall various conversations about how much radiation is given during SRT.

My RO specified 38 sessions, 1.8 GY each, for a total of 68.4 GY.

It was suggested that maybe that number should be higher as studies seemed to indicate better results on the PC front with even more radiation. Oddly, the MSK nomograph does not bear that out. When I vary the amount of GY with my other data, the highest probability of a non recurrence is right at 68.4. When I brought this up, it was stated that most likely the sample size is too small (at the higher levels) and so they can't get a reliable answer. Still, one would think that their nomograph should return a reading of "insufficient sample size" if that was the case.

Anyway, at my appointment today, I brought up the studies and asked my RO if it might make sense to do 1 additional session to up my dosage a bit. He was quite emphatic that 68.4 has been shown to be the best amount. He also pointed out that SE are factored in and that we are really also dealing with a risk/reward thing here. We want to kill the cancer, but not the patient. Anyway, that was interesting and it does appear that SE considerations are also very important in determining the proper dosage.

I might also add that in a previous thread about this I asked how much GY others were receiving and it did seem like quite a few were getting the 68.4 dosage.

Mel (hoping the dreaded SE do not occur!)

I had 66Gy (33 sessions). I asked why and they said that 66 was right for my situation, but I met (older) guys in the waiting room who were having more. My PSA has gone below 0.1 so 66 seems to have been enough.

I note that I was getting 2gy each day compared to your 1.8gy, which seems to be another inconsistency. I asked how they picked the daily dose as well, and asked why RT was not delecvered in say 11 sessions of 6Gy, or even 22 session sof 3gy and here they too mentioned the "kill the cancer, but not the patient" message.

They said the total and daily doses are calculated on the basis of what has been learned while giving RT to the patients treated in the decades before it was my turn. (They did not say what the old doses were, but I beleive that at the beginning of RT people were given many more Gy.)

As for SE, I hope you avoid as much as possible.

Alf

Mel, this is just speculation on my part, but what I think may be happening is this. After you set up all the numbers in the nomogram, it tells you the average response for patients with those numbers, the more patients the better for accuracy. When you up the Gys in the nomogram you are finding the average response not for you at that level, but for all patients that were treated at that level.

There are two issues. The first one, as you noted, is that there weren't as many at that level, so there is more noise in the results.

The second one is that those patients who got the higher Gys got them for a reason, probably more advanced cases for which the odds of radiation failure are higher. That may be why when you raise the Gys the odds of a cure come down. It's not that they really go down, but that the patients who got that high of a level were in worse shape. And, of course, the nomogram doesn't talk about the SEs they felt at that level.

I guess what this means to us as individuals is that for our specific numbers we need to find what has worked well for others with our same numbers.

The higher the dose the greater the killing power. This is a universal and undisputed fact in radiation. I asked my RO about the differences in nomograms and he said it was due to sample size errors. Reachout also gave some very good reasons for the difference. Also it's not just the dose but the area in which the dose is spread over. A very small pinpoint of cancer such as an indentified spot in the bed or the lympnode can get a much smaller dose than treating the entire bed and pelvic area.

There is a point where applying radiation becomes more of an art than a science. An experienced radiological team can get bettter results with less side effects and nomograms reflect the universe of surgeons and radiologists.

JT

Newporter:

Maybe it is aq custom tx?

When I spoke with the RO, it was about MY situation. He did say he looked carefully at the pathology report and surgeon's notes.

Incidentally, my guess is the reason for nothing above 68.4 GY really pertained to the SE profile.

Mel

Mel,

Thanks. That make sense. However, shouldn't the total dose be also machine dependent?

News:

Yes, he often mentioned the machine.

Mel

Having endured major radiation twice in 11 years, each time, I was told the dosing was based on the facts of that particular patient. Both times I went through the same radiation clinic, and the planning was based on my particulars. They don't do a standard dose. This time around, due to my quick surgery failure, and because of my PSA velocity issues, they went for the higher dose of 72 gys via 39 treatments. In the world of SRT, that's a high dose, though they do go up to 76 gys. With RT as a primary treatment, they go to 80 or a little over.

With radiation posioning, most people's bodies couldn't handle a dose larger than 2 gys a day regardless, the side effects would be greatly increased. That's why they don't do 3 or 4 gy daily dosing.

Surgery is strictly a mechanical act on the body, but radiation is another matter, and how each person's body can tolerate radiation and how its delivered is very unique.

I am afraid that some men take the prospect of radiation too lightly, and may end up jumping the gun in a SRT situation. If one needs it, then of course go for it, as its your final curative attempt for a surgery guy.

My terrible ordeal with SRT is not as rare as some think. I have read radiation horror stories that make what happened to me look like child's play. The percentages of bad outcomes may be low, but they still happen.

It's all in the planning phase, at least that is how it's suppose to work.

The advantage of IMRT supposedly is the narrow controlled beam, but after things started going downhill with mine, the Rad dr. finally admitted that due to a particurally narrow prostate bed, yes, a lot of scattering was taking place.

When I had radiation pre-IMRT, in the old days (year 2000 lol), they had to design special shields for me to protect parts of me that they didn't want the radiation to hit, including this weird contraption that protected my vocal cords. And the face mask I had to be strapped into each day was horrible.

David in SC

Absolutely, Fairwind.

I'm getting 72gys in 40 treatments for Adjuvant IMRT.
<bobr>
______________________
Age 54, Bx 3+/12, G9, psa 4.3, post surgery (pT3a, N0, MX), psa <0.1, Calypso RT in progress - 40 treatments

Thanks Purgatory - 5 more treatments to go after tonight ...then time for a PCa break.

Now I just need to talk either my Uro or my RO into getting a ultra-sensitive PSA test since I'ma ultra-paranoid G9 guy. I'm relatively new to the war having Robotic end of December and now ART. My post-surgery PSA is <0.1.
---------------
Age: 54
Routine Physical on 10-20-2010 DRE Normal
PSA 4.3, up from 0.6 5 years prior
PSA 0.6 on 10-25-2005
PSA 0.4 on 7-30-2004
PSA 0.5 on 5-9-2002
Followup with Urologist on 11/10/2010 after elevated PSA; DRE noted slight bump
November 30th, 2010 had prostate biopsy.
December 9th, 2010, Biopsy results 3 of 12 cores positive.
LLB: Gleason's 4+3=7, 11 MM Tumor Length/15MM Core Length (73%)
LLM: Gleason's 4+4=8, 12 MM Tumor Length/15MM Core Length (75%)
LM: 0.1 MM Tumor Length (1%)0.1 MM Tumor Length
Urologist recommended robotic removal using da Vinci method.
RALP Surgery 12/27/2010 Released: 12/30/2010
Thunderbird Banner Hospital, Glendale, AZ
Post-Surgery Pathology: GS 4+5=9
Pathologic Staging: pT3a, N0, MX; location: Left Side; Volume: 10%
Margins: Left posterior inked margin focally involved
Extraprostatic Extension: Observed
Seminal vesicles: Not observed
Lymphatic/Vascular Invasion: Not observed
Catheter: Removed 15-days after surgery
Post-OP Followup on 1/11/2011; Catheter/Staples removed
Adjuvant IMRT 8 Weeks Post-OP.
No exercise for 4 Weeks Post-OP.
Radiation Oncologist Initial Consultation on 1/18/2011
Calypso Procedure on 2/17/2011; PSA <0.1; Bone Scan Clear
341 Testosterone
CT Simulation on 2/24/2011.
Calypso ART in progress - 40 treatments ending 3/3/2011