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What is the EBRT Target area?

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Posted 10/15/2018 3:00 AM (GMT 0)
What is the typical EBRT target area for a T1C?

I would think prostate, plus a couple of mm of margin, plus seminal vesicles.

Reason I’m asking is, if as an Intermediate favorable, with no SVI, no LNI, and no EPE, if I’m doing HBR or SBRT, and if it provides a high dosage to the prostate, plus a little margin, plus the lower part of the seminal vesicles, what is the purpose of an EBRT boost?
(unless we’re just going to flame it again, plus hit the pelvic bed without even knowing if there’s anything there).

Thanks!!
Posted 10/15/2018 3:27 AM (GMT 0)
Prostate, margins, or anything else that came up on the scans before treatment starts.

The idea with doing both is to cover the margins, and get more radiation into the prostate than can be done with a single treatment mode. It also ensures that no part of the prostate is missed as can happen if the Brachy seeds aren't placed just right or if there is a gap in radiation coverage.

The combo therapy is generally for higher risk patients. Low or intermediate favorable risk patients can just do one RT method and be effective.
Posted 10/15/2018 12:00 PM (GMT 0)
Hi LUV, I would ask your RT, as they all do it a little different. The goal of radiation therapy is to maximize radiation to the prostate and to avoid radiating surrounding normal tissue. I would expect, as In-the-Shop has stated that someone like you with a favorable intermediate would not have any need for targeting the surrounding area and instead the RT has developed an algorithm to take dead aim at the middle of your prostate. Using a daily CAT Scan the EBRT machine will shape the beams and aim them at the prostate from several angles. Of course you also have the choice of various radiation intensity for each treatment and that will determine how many treatments you need. In my case, the RT is targeting around the edges of the prostate rather than directly in the middle. I have an odd shape small prostate due to a TURP and 6 months on Lupron. I also had a SpaceOar injection which provided a little more space. The Lupron or ADT according to my last T3MRI interpretation "mildly diffusely decreased T2 signal throughout, consistent with interval hormone therapy. The focal 1.8 cm PI-RADS 5 lesion seen within the right mid gland extending into the base and apex on the prior MRI is no longer visualized as a focal lesion." I assumed in my case the RT is making sure the high dose gets all the cancer by targeting the edges. I didn't think RT was all that complicated but apparently it is.


68 yrs., marathon runner, 14 of 44 3D-CRT/IMRT Radiation delivered via 3D-CRT in 1.8 Gy minimum dose fractions to a total of 79.2 Gy., 10.5.18. PSA .012, 8.12.18, 1.42 June 18, 2018 (Lupron 5.21.18 & 8.15.18), 12.7 May 2018, 13.7 Jan. 2018, 2.1 May 2012. SpaceOar 9.6.18, testosterone <.7, 8.15.18, Tot Mayo 19 ng .17 testosterone Free 6.18.18, Gleason 3+4=7 involving 15% of the right apex and 15% of the right mid, 3+3=6 prostate cancer involving 5% of the left base. Pathology interpretations by John Hopkins, UNM Cancer, and SF Path 3+4=7 or 4+3=7 MD Anderson Proton Center w/o %. T3 MRI w/ contrast 1.8 lesion left side 5P, Neg. Bone Scan. Prolaris test 3.5 consistent with intermediate and a PTEN test negative. Father PC age 78 RT & ADT now 93 yrs. Neurogenic bladder due to lumbar disk disease and recurrent bladder neck contracture with urinary retention man. 20 years doing catheterizations. TURP & scaring 2003, Finasteride 5 milligrams daily since 2002.
Posted 10/15/2018 1:20 PM (GMT 0)
While there are general guidelines, your radiation team will work up the area specific to your anatomy and cancer. My RO was happy to show me the treatment plan called the dosimetry. He introduced me to the physicist and dosimetrist and they presented the plan to me. All very interesting and boosted my confidence.

All your questions are what you need to be asking the RO and team members.
Posted 10/15/2018 2:34 PM (GMT 0)
Thank you all for the replies.

Andrew, I'm hoping that my RO will agree that HDR as a monotherapy provides a high PFS and that this question of EBRT target area will become moot. I've wondered about the point that you made about inaccuracy or inadequate coverage. However, my reading has lead me to believe that with properly performed HDR, there should be no known missed areas of radiation because the purpose of HDR over LDR is largely to avoid the potential variations with LDR (shifting of seeds and other potential variations).

Additionally, since the BED (Biological Effective Dosage) to the prostate is typically much higher with ultrafractionated HDR than is usual in EBRT, I'm missing the need for the extra radiation of the prostate.
(BED in the range of 237–354 Gy for HDR vs the BED of 178 Gy achieved with EBRT)

I hope to be able to have these discussions with the selected RO once we're finished collecting data from the secondary biopsy review and the Decipher test, but I'm hoping to go into that discussion more informed in order for it to be more productive (I've found I'm just not as agile on my feet when they throw new info at me - I need time to digest and research it).

SantaZia: sounds like you're in the midst of it. Best wishes for successful treatment!
Posted 10/15/2018 2:42 PM (GMT 0)
Here is a great website for understanding HDRBT. www.cetmc.com. It is the site of Dr. Jeffrey Demanes, the HDRBT pioneer and head of the department at the UCLA Medical Center. It addresses many of the questions you have and will aid your research.
Posted 10/15/2018 6:05 PM (GMT 0)
Awesome / thanks Jack!!
Posted 10/16/2018 10:05 AM (GMT 0)
I was told that the whole prostate plus an area surrounding the prostate of ~2mm and about 1cm of the seminal vesicles is the usual target area. In my case the RO extended the SV treatment area to 2cm because of where my tumor was located.
Posted 10/16/2018 1:50 PM (GMT 0)
My primary RT for a high risk case with some MRI evidence of extracapsular extension (cT3a, arguably cT2b) was IGRT by IMRT, external beam only. They also hit my pelvic lymph nodes due to a 40% chance of undetectable involvement already. I don't know if these margins would have been any different with a T1c or not, but sharing this for what it's worth.

Dose plan was 50.4 Gy to lymph nodes with 10mm margin, and 79.2 Gy to prostate with 6mm margin (except at back side of prostate next to rectal wall it was 4mm).

So far so good. Next PSA check is tomorrow.
Posted 10/16/2018 3:43 PM (GMT 0)

hrpufnstuf said...
I was told that the whole prostate plus an area surrounding the prostate of ~2mm and about 1cm of the seminal vesicles is the usual target area. In my case the RO extended the SV treatment area to 2cm because of where my tumor was located.

Thanks for the info and the context from your signature. Looks like your PSA history is going as is often typical with a little bounce and then settling down. Best wishes that things stay on track.

Following up on the intent of determining the need for combined therapy, the NCCN guidelines were recently updated and the Favorable Intermediate Risk category officially now has a treatment recommendation option for HDR as a monotherapy for some patients.

From looking at UCLA and CET Brachy programs (thanks Jack!), it looks like they consider G7 (3+4) patients as candidates if the cancer volume is low <50%.
I’m at 6/12 cores and so it appears to me (and I expect certain RO’s will agree) that it could go either way - can do as a monotherapy, but surety of cure goes down compared to combined therapies).
I guess the thought being - as was mentioned earlier on this thread - that if the risk is higher, you combine the internal therapy with EBRT to give a higher total dose to the prostate (and margins) to fry the heck out of it and studies seem to reflect doing so increases PFS (albeit at the risk of greater late term side effects).

Sigh....keeping fingers crossed as we await secondary BX slide review from UCSF and Deicpher test results.
Posted 10/16/2018 3:47 PM (GMT 0)

Redwing57 said...
My primary RT for a high risk case with some MRI evidence of extracapsular extension (cT3a, arguably cT2b) was IGRT by IMRT, external beam only. They also hit my pelvic lymph nodes due to a 40% chance of undetectable involvement already. I don't know if these margins would have been any different with a T1c or not, but sharing this for what it's worth.

Dose plan was 50.4 Gy to lymph nodes with 10mm margin, and 79.2 Gy to prostate with 6mm margin (except at back side of prostate next to rectal wall it was 4mm).

So far so good. Next PSA check is tomorrow.

Thanks for the feedback and best wishes for calm nerves as you await the next PSA results (looks like it has settled to a nice place and is rock steady)
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