I have a consultation with a RO on Friday for SBRT in Boston.
What questions should I ask pertaining to the planned target volume and the margins in each area?
I hear +2 to 3 mm in some areas and close to zero between the Prostate and rectum. Could someone clue me in on what to ask, do they specify margin for different areas and if so what are the areas should I ask about
As I understand it, the Planned Target volume is the GTV + margin( gross tumor volume + margin, which could include the seminal vesicles in the GTV). Is the margin due to some inaccuracy or movement of the organs or is it added outright and on top of that there can be some larger volume due to inaccuracy?
I have about
a 4-7% risk of SVI+ according to the MSK and JH, depending on which you believe, would that dictate treating them or do they always treat them with beam RT, if they do treat is there more risks?
Are the nerve bundles included in this margin ie 2-3 mm?
My concern from my nomograms I have 30%(john Hopkins partin table) to 66% chance(MSK nomogram) of ECE and don't really have a feel for how the RO's treat for someone with my risk, PSA 8.1, 2 of 13 cores GL 3+4 ( 35% Involvement, 90% Gl3 and 10% Gl 4) and 4 of 13 (20-35% Involvement) GL 3+3 and T2A, all on the right side.
If they suspect heavy ECE do they
open up the margins. I am favorable intermediate.
Also for dose constraints, how does one ask about
that? I have read they do the does constraint for the bladder, rectum, penile bulb, urethra?
I read one paper for a 81 Gy 45 dose the DVH for this IMRT was below. They used CBCT daily between fractions, 45/1.8
V75 Gy < 15% meaning less than 15% of rectum receives 75 GY
V70 Gy < 20%
V65 Gy < 25%
V60 Gy <35%
V50 gy < 50%
with the max dose < prescript
V80 Gy <= 15% of bladder receives 80 Gy
V75 Gy <= 25%
V70Gy <= 35%
V65 GY <= 50%
What would one expect with SBRT with the fiducials, Cyberknife lower DVH limits than above? and is this how they present them.
What does the Urethra receive generally on a SBRT with 35-36.25 GY?
A link with some info on CBCT and contouring.
Sorry for all the questions.
Post Edited (Turboz) : 11/13/2017 8:50:15 AM (GMT-7)