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Medical Forum / Diseases and Disorders / Prostate Cancer / February 2007Dosimetry (CT scan)
Those web pages that I visited looking for an explanation of D90 dosimetry was just too technical. The oncologist called yesterday to say my D90 was 130, and a very good reading. He suggested it might be too technical for me to understand, and would review it with me on my next visit in a couple of months. Can anyone provide some insight into this? On Jan 31, 1:58 pm, "3Putt from South Carolina" <3putt@secoastofsc> wrote: > Those web pages that I visited looking for an explanation of D90 dosimetry > was just too technical. The oncologist called yesterday to say my D90 was > 130, and a very good reading. He suggested it might be too technical for me > to understand, and would review it with me on my next visit in a couple of > months. Can anyone provide some insight into this? Hi 3Putt...As I understand it, D90 is the dose delivered to 90% of the prostate volume as measured by postimplant dosimetry. So in your case it sounds like 90% of your prostate received about 130 grays. Some questions to ask the doc might include.. What dose were you trying to achieve? Are there any areas in the prostate that received / are receiving a significantly higher or lower dose? Did any surrounding areas receive a significantly higher dose that projected? Are all the seeds in place and accounted for? I'm not sure what would be "significant", maybe 25%...Best wishes and good health, ron > On Jan 31, 1:58 pm, "3Putt from South Carolina" <3putt@secoastofsc> > wrote: [quoted text clipped - 9 lines] > it sounds like 90% of your prostate received about 130 grays. Some > questions to ask the doc might include.. As I am going through RT treatment myself at the moment, the dose rate, if this explanation is correct seemed awfully high. My findings on IMRT ranges from 74-79 Gy (cumulative), and some studies has shown that first treatement of less than 73 Gy may not kill all the cancer. High Dose brachytherapy aims for 40-60 Gy total n 2 fractions. My SBRT protocol aims for 45 Gy, cumulative, in 5 hypofractions, thus similar to HDR Brachy. Can someone more knowledgeable explain? > > On Jan 31, 1:58 pm, "3Putt from South Carolina" <3putt@secoastofsc> > > wrote: [quoted text clipped - 22 lines] > similar > to HDR Brachy. Can someone more knowledgeable explain? IMRT ranges are going to be different than Seed Implant Dose ranges. Seed Implants allow you to give a larger dose to the Prostate, while giving a limited dose to the Rectum and Bladder (Critical Structures). Where as IMRT can Limit dose to critical Structures but only to a certain degree. The energy of the Photons (Radiation) is different, for IMRT than it is for seed implants. Seed implants have a lower energy; therefore the energy is deposited locally. As for the other HDR procedures you are talking about I would need more information to elaborate. Also Noted should be that for certain stages of Prostate cancer certain modalities show a better result. > > > On Jan 31, 1:58 pm, "3Putt from South Carolina" <3putt@secoastofsc> > > > wrote: [quoted text clipped - 35 lines] > > - Show quoted text - I am well aware of brachytherapy to IMRT/IGRT differences. I also know the differences between permanent versus HDR where the energy is only exposed to the prostate for minutes then withdrawn. My question is about the "130" Gray. I believe that this is unheard of for brachytherapy. > My question is about the "130" Gray. I believe that this is unheard of for brachytherapy. My doctor told me my combined iodine seeds plus EBRT inside the prostate was over 200 Grays. John On Feb 1, 8:33 pm, "cmdrdata" <cmdrd...@mail.com> wrote...snip... My question is about the "130" Gray. I believe that this is unheard of for brachytherapy Looking at some of Radge's and Blasko's papers I see that doses upt to 160 gy are administered with I125 seeds (lower doses with Pd seeds) depending upon PCa risk classification. When they do SI+XBRT the combined dose is typically around 200 gy as John H. reports...Best wishes and good health, ron . Hi again 3Putt...I was looking at the Zelefsky paper mentioned in Curtis' post this am. Zelefsky notes, "Among patients where the I-125 dose to 90% of the prostate (D90) was >/=130 Gy, the 8-year PSA relapse-free survival (PRFS) was 93% compared with 76% for those with lower D90 dose levels (p < 0.001)"..Best wishes and good health...ron > Hi again 3Putt...I was looking at the Zelefsky paper mentioned in > Curtis' post this am. Zelefsky notes, "Among patients where the I-125 > dose to 90% of the prostate (D90) was >/=130 Gy, the 8-year PSA > relapse-free survival (PRFS) was 93% compared with 76% for those with > lower D90 dose levels (p < 0.001)"..Best wishes and good health...ron Thanks Ron. I've my first after treatment PSA 1st week of April and visit with the urologist a few days after. Meanwhile my wife has had an MRI last week, CT and sonogram today as a 3 month followup to breast cancer treatments. Some problem areas showed up, but we refuse to dwell on the issues and get on with our lifes. |
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