Prostate Fossa PTV

[deleted4401]

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I use the consensus volumes for CTV and then add 0.8cm in all directions and 0.6 posteriorly, CBCT daily and try to match to the bladder/rectum. My clever dosimetrist has taken to looking up the RTOG protocols for his own edification for constraints and was looking at their PTV margins. 0.8cm - 1.5cm in all directions!! 0.6cm for posterior is an acceptable minor deviation. Below 0.6cm is an major deviation. I didn't realize I was so tight - I'm usually on the upper end of suggested margins.

Are you guys using these huge PTV expansions? It might be worthwhile to do an empty bladder/full bladder scan to account for anterior variation, but I usually just include the posterior 1-1.5cm of the bladder.

Simul

 

[Gfunk6]

I do exactly what you do. Keep in mind that RTOG 0534 was created nearly a decade ago and does not mention any form of IGRT other than (presumably) weekly ports. With daily CBCT, fiducials, BAT, et. al. we should be able to reduce the margins per your institutional guidelines.

I usually try to include the whole bladder since the SV remnant can extent quite cranially and would be impacted by variations in bladder fill.

 

[medgator]

Are you guys using these huge PTV expansions? It might be worthwhile to do an empty bladder/full bladder scan to account for anterior variation, but I usually just include the posterior 1-1.5cm of the bladder.
Simul

I do exactly what you do. Keep in mind that RTOG 0534 was created nearly a decade ago and does not mention any form of IGRT other than (presumably) weekly ports. With daily CBCT, fiducials, BAT, et. al. we should be able to reduce the margins per your institutional guidelines.

I usually try to include the whole bladder since the SV remnant can extent quite cranially and would be impacted by variations in bladder fill.

I usually do 1 cm, 0.8 cm posteriorly. Per the RTOG guidelines, they recommend including the whole bladder at least along the symphysis and the posterior 2 cm of bladder wall at the minimum above that.

 

[deleted4401]

Yeah, but can't do fiducials or BAT when there is no prostate. The CBCT is sort of guess work and there isn't much literature on this. It's kind of an odd situation, as it is becoming more and more common b/c of the adjuvant RT trials, but not much clear data on PTV.

 

[Gfunk6]

Yeah, but can't do fiducials or BAT when there is no prostate. The CBCT is sort of guess work and there isn't much literature on this. It's kind of an odd situation, as it is becoming more and more common b/c of the adjuvant RT trials, but not much clear data on PTV.

True, but you do have plenty of surgical clips.

 

[Kroll2013]

I do the same also.
Another question could be asked is what PTV to take around CTV LN when you are treating Pelvis + prostatic Bed.
would you choose to match your CBCT on The prostatic bed CTV and take 1 cm PTV around CTV LN? or match on the Pelvis for the first 45 Gy , which means extending PTV margins around CTV prostatic bed?

 

[Seldon1985]

I do the same also.
Another question could be asked is what PTV to take around CTV LN when you are treating Pelvis + prostatic Bed.
would you choose to match your CBCT on The prostatic bed CTV and take 1 cm PTV around CTV LN? or match on the Pelvis for the first 45 Gy , which means extending PTV margins around CTV prostatic bed?

Are you all using a rectal balloon with these expansions? My institution uses 7mm with 5mm posteriorly....

 

[thesauce]

We never treat pelvic + prostate bed. Just Michalski + 8 and 5.

 

[medgator]

We never treat pelvic + prostate bed. Just Michalski + 8 and 5.

Not even in N1?

 

[thesauce]

Not even in N1?

If they were pN1 in addition to having a clear adjuvant or salvage RT indication, we would give ADT, but I don't think we would treat the pelvis. I can think of one faculty that probably would, but not the others.

 

[Palex80]

We treat the pelvis in pN1-patients. There is a retrospective Italian study with most of the patients treated with pelvis RT, showing quite good results with such an approach: PMID: 19211184