Salvage RT Prostate with Intestine In the Way

[Haybrant]

Had a young patient (56 yo) who had prostatectomy last year for Gleason 3+4 with low PSA in early ‘21. He had positive margin at the right base on path and had SVI bilaterally. PSA was negative after surgery for 5 measurements then rose to detectable but still low at .05 then .06 a couple months later. He had a PSMA which was negative and was referred to talk about early salvage. Fairly anxious patient who very much wanted RT. Urology sent him to a med onc too, bc of such low PSA they opted against ADT.

I sim’d him and of course he has a loop of small bowel hanging very low (lot of bowel in general low), I did 4500 and conedown to 7020 as superior as I could while staying within tolerance. I fused the pre surgical MRI and where the base (and majority of SV) were aren’t covered in the 7020, more like 5500 at the low base and 4500 at the high base (median lobe that pushed into the bladder)

Appreciate thoughts on management, would you just proceed as is and maybe ask med onc to reconsider ADT. I don’t think prone is going to get that bowel out of there it is pretty down behind the bladder.

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[Mandelin Rain]

How full is the bladder?

Sometimes, if guys with post-op incontinence, you can give a penile clamp to help fill bladder to displace bowel loops.

 

[thecarbonionangle]

How high is your bowel dmax now? How conservative are you being?

 

[deleted1116990]

These cases are challenging.

First, you don't need to go to 70. You can stop at 66 or even 64 if you want.

I have tried simming prone. It helps a little but not a lot. I go ahead and treat prone because any little bit helps.

Third, the PSA is low. Why not wait until it gets to the 0.2-0.3 range and repeat PSMA and see if you can find out where the disease is so you have less worry about trimming the traditional salvage field around the bowel, then boost the gross disease to 76 while taking everything else to 66.

 

[thecarbonionangle]

These cases are challenging.

First, you don't need to go to 70. You can stop at 66 or even 64 if you want.

I have tried simming prone. It helps a little but not a lot. I go ahead and treat prone because any little bit helps.

Third, the PSA is low. Why not wait until it gets to the 0.2-0.3 range and repeat PSMA and see if you can find out where the disease is so you have less worry about trimming the traditional salvage field around the bowel, then boost the gross disease to 76 while taking everything else to 66.

Tendulkar nomogram data suggests this is not a great strategy generally. This patient is young with positive margins (good prognostic indicator), I would hate ro reduce the chance of cure by waiting for PSA to get above 0.2

 

[deleted1116990]

Tendulkar nomogram data suggests this is not a great strategy generally. This patient is young with positive margins (good prognostic indicator), I would hate ro reduce the chance of cure by waiting for PSA to get above 0.2

Fry the bowel then. Waiting for the PSA to get to 0.2-0.3, given that we twist ourselves into pretzels to justify AS in intermediate risk patients, is likely not going to make a huge difference. Additionally, in the PSMA era, it is possible that waiting will allow you to identify disease location that you can treat to a definitive dose that you otherwise would not have been able to. No, I don't have retrospective data for that.

 

[Haybrant]

Patient is very anxious won’t accept waiting but it’s a good point did think about it and can rediscuss it given the issues. Bladder is full he doesn’t have problem with incontinence. Bowel dmax is 49 now. Remember he was high risk due to both SVs invaded at surgery

 

[thecarbonionangle]

Take a bowel dmax of 60 and see how the plan looks?

 

[jondunn]

These cases are challenging.

First, you don't need to go to 70. You can stop at 66 or even 64 if you want.

I have tried simming prone. It helps a little but not a lot. I go ahead and treat prone because any little bit helps.

Third, the PSA is low. Why not wait until it gets to the 0.2-0.3 range and repeat PSMA and see if you can find out where the disease is so you have less worry about trimming the traditional salvage field around the bowel, then boost the gross disease to 76 while taking everything else to 66.

I don’t see the reason to wait

 

[deleted1116990]

I don’t see the reason to wait

To not put a loop of bowel in the 70 Gy field? Sorry if that was not clear.

Alligator is correct, only option now is to dose paint around it, although we all know some Boomers that would just rubber stamp the contours the dosimetrist drew on it and have no idea the bowel was getting 70 and the patient would probably be ok.

 

[Ray D. Ayshun]

can you sim the patient prone? I had this issue, and that fixed it.

Edit: oops, just read you thought about it. Either way, might be surprised. Treat the primary field supine and the boost prone. Have fun with it!

 

[TheWallnerus]

I would love to see some images especially sagittal

 

[Haybrant]

Thanks for the suggestions.

 

[jondunn]

To not put a loop of bowel in the 70 Gy field? Sorry if that was not clear.

Alligator is correct, only option now is to dose paint around it, although we all know some Boomers that would just rubber stamp the contours the dosimetrist drew on it and have no idea the bowel was getting 70 and the patient would probably be ok.

You can trewt now and not give the bowel 70 gy.

 

[Ray D. Ayshun]

Was just trying to get permission to roast the bowel the other day and i think crane was doing a dmax of 55/25 for the small bowel. Thats a BED2 equivalent to 64.6 Gy in 38,

 

[Haybrant]

Thanks for the suggestions attaching 2 pictures one shows the amount of small bowel there so prone is a good idea but also wonder if it won’t be so accommodating bc of the amount of it sitting anterior. Purple is 45 orange is 70

Also would you add adt? Would you sim prone first see how it goes then decide on ADT. Also just curious in salvage cases with adt do you guys wait the two months still to start RT?

 

[TheWallnerus]

Thanks for the suggestions attaching 2 pictures one shows the amount of small bowel there so prone is a good idea but also wonder if it won’t be so accommodating bc of the amount of it sitting anterior. Purple is 45 orange is 70

Also would you add adt? Would you sim prone first see how it goes then decide on ADT. Also just curious in salvage cases with adt do you guys wait the two months still to start RT?

I think you’re prob gonna be fine to treat as is

No need to add in the drama of prone sim and tx if don’t have to

A teeny tiny amount of cheating in the very tippy top of your PTV in propinquity to bowel wouldn’t be the end of the world if you HAVE to do that, but I bet the DVH looks fine right now

 

[Mandelin Rain]

Learned a new word today. GREAT SUCCESS!

 

[Haybrant]

I think you’re prob gonna be fine to treat as is

No need to add in the drama of prone sim and tx if don’t have to

A teeny tiny amount of cheating in the very tippy top of your PTV in propinquity to bowel wouldn’t be the end of the world if you HAVE to do that, but I bet the DVH looks fine right now

I think you’re prob gonna be fine to treat as is

No need to add in the drama of prone sim and tx if don’t have to

A teeny tiny amount of cheating in the very tippy top of your PTV in propinquity to bowel wouldn’t be the end of the world if you HAVE to do that, but I bet the DVH looks fine right now

Thoughts on adding ADT?

 

[thecarbonionangle]

Thoughts on adding ADT?

Can add based on SPORT/getug/rtog trial, can omit based on Spratt analysis showing less benefit in and more cardiac issues in patients <0.6.

Are you going to treat pelvic nodes?

 

[Ray D. Ayshun]

Can add based on SPORT/getug/rtog trial, can omit based on Spratt analysis showing less benefit in and more cardiac issues in patients <0.6.

Are you going to treat pelvic nodes?

Likely a better benefit to toxicity ratio for adt in this case versus treating pelvic nodes

 

[Ray D. Ayshun]

Deleted

 

[TheWallnerus]

Thoughts on adding ADT?

I’m an adder almost always in postop at least for 6mos. (There are some Stage I hnscc at MDACC that get concurrent chemoRT…) The hormones are not nec a walk in the park but the data points toward better outcomes as we all know.

 

[Palex80]

We have faced the same issue in the past and usually resorted to giving a bowel constraint of 60 Gy and planning.

We do however do this as well:
We scan these patients several times during the treatment course (mostly one weekly) to be certain that the initial planning CT represents daily anatomy and is not misleading. We generally do this immediately before / after a daily treatment without letting the patient void in between. We fuse these repeat CTs with the initial planning CT, draw the "new" bowel into the initial planning CT and thus end up with multiple DVHs for every "bowel-scenario". From time to time, you may find that the bowel loop magically disappears or moves to a more (or less!) favorable location in the pelvis. After 5 weeks of treatment (at around 50 Gy) we have half a dozen bowel DVHs and can estimate what the cumulative dose was and how much we want to push our constraint. We then make the final and either go on with the set constraint or, if it's violated, cone down after 50 Gy to a smaller volume. In your case this would generally mean to crop PTV in the initial seminal vesicle region, which you would rather not do, since this was a pT3b tumor.

You may call this workflow "poor (wo)man's adaptive RT". I imagine that these patients would benefit from online adaptive RT (either CT- or MR-based).

If you can't acquire a sufficient dose into your PTV, I would certainly add ADT.

Just the day before yesterday, I faced a similar problem in a patient receiving intracavitary brachytherapy for cervical cancer.
One small bowel loop ended up between sigma and uterus, ruining an otherwise perfect treatment plan.
It was the MRI that actually picked it up, I later realized that I may have not identified it correctly on the CT only.

 

[Haybrant]

Do you guys wait 2 months in salivate setting after ADT to start RT?

 

[Ray D. Ayshun]

Do you guys wait 2 months in salivate setting after ADT to start RT?

I don't. I usually give it at sim if theyre a ways out from surgery/urinary function has stabilized.

 

[seper]

In these types of postop cases my experienced partners a) treat prone (if you have a bellyboard); b) resim after 40-45 Gy

 

[jondunn]

In these types of postop cases my experienced partners a) treat prone (if you have a bellyboard); b) resim after 40-45 Gy

how often does a resim change anything in this scenario?

 

[Palex80]

how often does a resim change anything in this scenario?

I would say 20%, when done the way we do it (described above). 10% bowel moves out of the way at some point, 10% more bowel drops into small pelvis ( often happens when cystitis kicks in and <full bladder for RT> becomes an issue).

 

[DoctwoB]

I don’t see the reason to wait

Depends on the patient/margin. If he had a focally positive gg1 Margin or even benign tissue at Margin this may be a recurrence that never becomes clinically significant. Say the doubling time is 18 months or 2 years.

Arguing against that is he’s young and anxious and t3b disease. Certainly reasonable to salvage. Could also get another PSA or two first to assess the trend. Plenty of room to do that and still salvage at <0.2

 

[Burt Radnolds]

Do you guys wait 2 months in salivate setting after ADT to start RT?

Spratt had some data out recently that seemed to suggest adjuvant was better than neoadjuvant. I know he used intact prostate studies but a very reasonable extrapolation. Not sure how much I believe it or not (Sorry Dan!) but it has crept into my brain. I'm more likely to get the radiation going quicker now in most settings, unless there is a reason to wait like huge gland, continence recovery, or prepaid European vacation.

Prostate Radiotherapy With Adjuvant Androgen Deprivation Therapy (ADT) Improves Metastasis-Free Survival Compared to Neoadjuvant ADT: An Individual Patient Meta-Analysis - PubMed

The sequencing of ADT with prostate-directed RT has significant association with long-term PFS and MFS in localized PCa. Our findings favor use of an adjuvant over a neoadjuvant approach, without any increase in long-term toxicity.

pubmed.ncbi.nlm.nih.gov

 

[DoctwoB]

Spratt had some data out recently that seemed to suggest adjuvant was better than neoadjuvant. I know he used intact prostate studies but a very reasonable extrapolation. Not sure how much I believe it or not (Sorry Dan!) but it has crept into my brain. I'm more likely to get the radiation going quicker now in most settings, unless there is a reason to wait like huge gland, continence recovery, or prepaid European vacation.

Prostate Radiotherapy With Adjuvant Androgen Deprivation Therapy (ADT) Improves Metastasis-Free Survival Compared to Neoadjuvant ADT: An Individual Patient Meta-Analysis - PubMed

The sequencing of ADT with prostate-directed RT has significant association with long-term PFS and MFS in localized PCa. Our findings favor use of an adjuvant over a neoadjuvant approach, without any increase in long-term toxicity.

pubmed.ncbi.nlm.nih.gov

Ironic given Spratts Twitter tirades against using anything other then primary RCT data. I’m not going to lie I read a lot of papers and was having trouble understanding how he obtained and massaged the data. It seems like he was looking at individual data from ADT trials, not adjuvant vs salvage trials?

On the other hand, RAVEs and RADICALS are very clear. 2 big modern RCTs with not even a trend towards difference between adjuvant and early salvage with >50% avoiding radiation.

 

[Ray D. Ayshun]

If we use psadt as a metric for post-op salvage in a 56 yo, why not use it pre-op for surgery? Protect showed no os benefit to anything in this guy right?

 

[medgator]

If we use psadt as a metric for post-op salvage in a 56 yo, why not use it pre-op for surgery? Protect showed no os benefit to anything in this guy right?

It's all about who controls the patient flow, that's why

 

[DoctwoB]

If we use psadt as a metric for post-op salvage in a 56 yo, why not use it pre-op for surgery? Protect showed no os benefit to anything in this guy right?

Protect showed MFS improvement which at this age (and data validates) is a survival benefit.

You may be being disingenuous on the latter point but I’ll bite. There’s a big difference between change in disease volume between a PSA from 0.05 and 0.1 and from 6 to 12 or 15 to 30. I’d suspect met rate much higher for the latter. Look at RCC. Met rate going from 1 to 2cm is negligibly low. Going from 3 to 6 cm Is dramatically higher.

 

[DoctwoB]

It's all about who controls the patient flow, that's why

It’s also about time following patients and experience. I’ve had patients go from undetectable to detectable PSA and then back again several times. PSA fluctuates more then we care to admit for reasons we don’t really understand beyond hand waving about residual benign tissue and prostatitis Voodoo. It’s also about balancing post op recovery time with the benefits of salvage xrt.

So while salvage xrt is absolutely underused or often used too late, it’s also not a matter of “whoop, PSA is .04, let’s fire up the cobalt”

 

[jondunn]

It’s also about time following patients and experience. I’ve had patients go from undetectable to detectable PSA and then back again several times. PSA fluctuates more then we care to admit for reasons we don’t really understand beyond hand waving about residual benign tissue and prostatitis Voodoo. It’s also about balancing post op recovery time with the benefits of salvage xrt.

So while salvage xrt is absolutely underused or often used too late, it’s also not a matter of “whoop, PSA is .04, let’s fire up the cobalt”

It’s the entire story dude.

Positive margin. Negative for a while. Now rising. Sure you can wait until 0.07 and 0.08 - but the story checks out.

 

[Palex80]

Protect showed MFS improvement which at this age (and data validates) is a survival benefit.

One simply delays the point that metastases pop up in a big proportion of patients. The key question is: do you truly cure additional patients by adding ADT and which are these patients?

 

[Ray D. Ayshun]

Wouldn't staging everyone on Protect with a PSMA PET pre-randomization also increase MFS?

 

[deleted1116990]

It's funny.

Chemotherapy is directly cytotoxic.

Never once have I had a patient ask me how taking away his testosterone kills cancer cells. They are satisfied with the analogy of "taking away the fuel for the cancer."

 

[DoctwoB]

Wouldn't staging everyone on Protect with a PSMA PET pre-randomization also increase MFS?

It would. Will Rogers effect. But that would be in all 3 cohorts of the study

 

[Ray D. Ayshun]

It would. Will Rogers effect. But that would be in all 3 cohorts of the study

Sure, but there's only so much closer to 0 you can get in that trial.

 

[RSAOaky]

Thanks for the suggestions attaching 2 pictures one shows the amount of small bowel there so prone is a good idea but also wonder if it won’t be so accommodating bc of the amount of it sitting anterior. Purple is 45 orange is 70

Also would you add adt? Would you sim prone first see how it goes then decide on ADT. Also just curious in salvage cases with adt do you guys wait the two months still to start RT?

The yellow contour in the pre-sacral space looks more rectosigmoid than true bowel but hard to say without seeing axials. I allow 60 Gy point dose to sigmoid. There's no sigmoid specific toxicity data so no one truly knows what to constrain it as even though we are often asked to contour it. Tolerance is likely closer to rectum than it is to bowel though (cervical brachy allows d2cc to both sigmoid and rectum of 65-70 Gy). Never had an issue.

 

[TheWallnerus]

The yellow contour in the pre-sacral space looks more rectosigmoid than true bowel but hard to say without seeing axials. I allow 60 Gy point dose to sigmoid. There's no sigmoid specific toxicity data so no one truly knows what to constrain it as even though we are often asked to contour it. Tolerance is likely closer to rectum than it is to bowel though (cervical brachy allows d2cc to both sigmoid and rectum of 65-70 Gy). Never had an issue.

/soapbox

How did point dose become a thing in plan evaluation. Point dose is meaningless for clinical outcomes. At best, it’s a marker for… what 10% or 20% or whatever of the organ is getting. I can give an 85 Gy point dose in one fraction to the skull base and a patient have zero side effects. Much more important is how much of an organ is getting how much of a dose or more. When I hear “60 Gy point dose to the sigmoid” I think: you would take 99.9% of the sigmoid getting 59 Gy?

/soapbox

 

[Palex80]

/soapbox

How did point dose become a thing in plan evaluation. Point dose is meaningless for clinical outcomes. At best, it’s a marker for… what 10% or 20% or whatever of the organ is getting. I can give an 85 Gy point dose in one fraction to the skull base and a patient have zero side effects. Much more important is how much of an organ is getting how much of a dose or more. When I hear “60 Gy point dose to the sigmoid” I think: you would take 99.9% of the sigmoid getting 59 Gy?

/soapbox

Well, it depends…

There are differences when it comes to parallel and serial OARs.

Point dose of 85 Gy in the chiasm, will likely cause toxicity, but not because of the 85 Gy but the 70 Gy that will probably encompass a relevant chiasm volume.
In other words: To achieve 85 Gy point dose to the chiasm, you need to give 70 Gy to a clinically relevant part of the chiasm.

Point dose is thus a surrogate marker for high dose to a relevant volume.
A bad one, however, I completely agree.

i generally use D0.1cm3 as a constraint, for instance for spinal cord.
I also „look“ at point dose, but do not view it as a constraint.

The Timmermann SBRT OAR tables also have a Dmax constraint.

 

[RSAOaky]

/soapbox

How did point dose become a thing in plan evaluation. Point dose is meaningless for clinical outcomes. At best, it’s a marker for… what 10% or 20% or whatever of the organ is getting. I can give an 85 Gy point dose in one fraction to the skull base and a patient have zero side effects. Much more important is how much of an organ is getting how much of a dose or more. When I hear “60 Gy point dose to the sigmoid” I think: you would take 99.9% of the sigmoid getting 59 Gy?

/soapbox

I 100% agree with the point you're making. However, having a max point dose still controls the remaining dose to the organ. For example, the hotspot in the sigmoid is going to be at the wall closest to the PTV. There is no way the contralateral wall is getting 59 Gy, and no way that 99.9% of the sigmoid is getting 59 Gy.

Well, it depends…

There are differences when it comes to parallel and serial OARs.

Point dose of 85 Gy in the chiasm, will likely cause toxicity, but not because of the 85 Gy but the 70 Gy that will probably encompass a relevant chiasm volume.
In other words: To achieve 85 Gy point dose to the chiasm, you need to give 70 Gy to a clinically relevant part of the chiasm.

Point dose is thus a surrogate marker for high dose to a relevant volume.
A bad one, however, I completely agree.

i generally use D0.1cm3 as a constraint, for instance for spinal cord.
I also „look“ at point dose, but do not view it as a constraint.

The Timmermann SBRT OAR tables also have a Dmax constraint.

Well I should have just read a bit further to see the same point being made except more elegantly.

Considering that OAR constraints dictate everything we do, we use surprisingly archaic constraint data.

 

[TheWallnerus]

I 100% agree with the point you're making. However, having a max point dose still controls the remaining dose to the organ. For example, the hotspot in the sigmoid is going to be at the wall closest to the PTV. There is no way the contralateral wall is getting 59 Gy, and no way that 99.9% of the sigmoid is getting 59 Gy.

/stillonsoapbox
Max point doses don’t control remaining dose to an organ. A planner must control remaining dose to the organ. There is every way,* including practically and mathematically, that a contralateral wall could get 59 Gy and that 99% of the sigmoid could get 59 Gy if the (only, or one of many) constraint is: max point dose to sigmoid of 60 Gy.
/stillonsoapbox

*if you had a very dumb, or very literal, dosimetrist. Or if you had an AI doing the dosimetry.

 

[jondunn]

You’re making a simple thing very complicated.

People look at max structures and volumetric structures as needed.

You’re acting like using a max for something like The bowel (which does matter) prevents one from also looking at other metrics?

There’s no rule that you can only look at one thing.

 

[RSAOaky]

/stillonsoapbox
Max point doses don’t control remaining dose to an organ. A planner must control remaining dose to the organ. There is every way,* including practically and mathematically, that a contralateral wall could get 59 Gy and that 99% of the sigmoid could get 59 Gy if the (only, or one of many) constraint is: max point dose to sigmoid of 60 Gy.
/stillonsoapbox

*if you had a very dumb, or very literal, dosimetrist. Or if you had an AI doing the dosimetry.

I think a more appropriate statement would be max points DO control the remaining dose to an organ, but there are situations where they don't. This is a situation where it does, unless you are going out of your way to make it not.

If you take issue with that then I guess we can agree to disagree.

 

[Palex80]

if you use a 2D field arrangement to treat a retroperitoneal follicular lymphoma with an IFRT approach using 30 Gy, you will end up with an „ok“ Dmax to the small bowel of a bit over 30 Gy. The issue is, that you will be giving 30 Gy to a lot of the small bowel too… it all depends on the technique used.