SpaceOAR while treating prostate + nodes

[seper]

If you are treating a high risk prostate cancer that requires adding B/L nodes (say, 50.4 Gy/28 to nodes and 70/28 to the gland), is there still a DVH benefit in pushing rectal gel? I have not seen enough plans to say. Thanks

---

Members don't see this ad.

 

[OTN]

I don't think there's ever any net benefit to the SpaceOAR

 

[seper]

I don't think there's ever any net benefit to the SpaceOAR

I agree if we are talking about "clinical benefit", "therapeutic ratio".
Unfortunately, incentive to do SpaceOAR does not seem to go away yet.
How about DVH benefit?

 

[elementaryschooleconomics]

I generally don't use SpaceOAR in high risk with nodes for two reasons:

1) I don't like SpaceOAR in high risk, no matter what. In patients where there is an increased risk of EPE, I cannot logically justify procedurally manipulating the area and potentially mixing microscopic disease into a gel which I'm trying to not include in my PTV. It just makes no sense to me.

2) While there's probably SOME benefit you could see on a DVH, if you're contouring nodes per consensus guidelines, I don't think this DVH benefit will definitively translate to a clinically meaningful benefit.

It obviously depends on your environment though. I know some academic departments where it's currently the cultural norm to do SpaceOAR on literally everyone, so perhaps you need to do it to survive chart rounds. I'm not in such an environment, so I get zero pushback for electing to not place SpaceOAR if I don't feel it's warranted.

 

[seper]

good point about mixing metastatic disease

 

[Ray D. Ayshun]

good point about mixing metastatic disease

Nobody really mentions it, but I believe SpaceOAR is only approved for T1 and T2. My approach is, anyone who's in the same risk group as a T3, aka high, is ineligible for SpaceOAR regardless of the reason they're high risk. I also don't give if there's imaging evidence of ECE or SVI, which it's still technically approved for. Just my approach as I'm looking for reasons to avoid it.

 

[Radonky]

I generally don't use SpaceOAR in high risk with nodes for two reasons:

1) I don't like SpaceOAR in high risk, no matter what. In patients where there is an increased risk of EPE, I cannot logically justify procedurally manipulating the area and potentially mixing microscopic disease into a gel which I'm trying to not include in my PTV. It just makes no sense to me.

2) While there's probably SOME benefit you could see on a DVH, if you're contouring nodes per consensus guidelines, I don't think this DVH benefit will definitively translate to a clinically meaningful benefit.

It obviously depends on your environment though. I know some academic departments where it's currently the cultural norm to do SpaceOAR on literally everyone, so perhaps you need to do it to survive chart rounds. I'm not in such an environment, so I get zero pushback for electing to not place SpaceOAR if I don't feel it's warranted.

I see your point, but with TRUS biopsies wouldn't you have expected a detrimental outcome too then? I am not aware of seeding or rectal recurrences from prostate cancer, and I imagine would probably would be the same for spaceOAR.

The problem with EPE in my (limited) experience is the anatomic barriers it creates, so its harder to get an optimal gel placed, if at all. If EPE is lateral its not much of an issue.

 

[elementaryschooleconomics]

I see your point, but with TRUS biopsies wouldn't you have expected a detrimental outcome too then? I am not aware of seeding or rectal recurrences from prostate cancer, and I imagine would probably would be the same for spaceOAR.

The problem with EPE in my (limited) experience is the anatomic barriers it creates, so its harder to get an optimal gel placed, if at all. If EPE is lateral its not much of an issue.

It's the risk/benefit ratio.

TRUS biopsy is how you confirm the diagnosis. You need it.

SpaceOAR is...to make the rectal DVH better? I've treated a lot of guys with and without SpaceOAR. I can't tell a huge difference in OTVs. I'm not super amped to jam more needles in the perineum to risk infection and rectal infiltration/fistula (yes, I am personally aware of more instances of this than that single case report) just to avoid telling a guy to go to Walmart and get a box of loperamide PRN.

@Ray D. Ayshun is correct. Of note, CMS guidelines only explicitly reimburse low and favorable intermediate risk (in practice, sometimes they'll do more without a fuss, depending on the benefit manager).

 

[Palex80]

I think there's still a DVH benefit, even when treating high-risk disease.
The reason why this may not translate into the same level of clinical benefit (clinical benefit being debatable at all with SpaceOAR) is that some of the quality of life metrics are not only rectum-associated. WPRT will always result into higher doses to cranial parts of the rectum and sigma, translating into higher rates of chronic GU toxicity and whether or not there's a SpaceOAR 10 cm lower at the level of the prostate or not, will not change colitis in the upper rectum/sigma.

 

[ramsesthenice]

I think there's still a DVH benefit, even when treating high-risk disease.
The reason why this may not translate into the same level of clinical benefit (clinical benefit being debatable at all with SpaceOAR) is that some of the quality of life metrics are not only rectum-associated. WPRT will always result into higher doses to cranial parts of the rectum and sigma, translating into higher rates of chronic GU toxicity and whether or not there's a SpaceOAR 10 cm lower at the level of the prostate or not, will not change colitis in the upper rectum/sigma.

I’ll take it a step further. SpaceOAR, like protons, suffers from overhype and unreal expectations. It’s not magic. Even in prostate only cases the only realistic thing it does for you (which it does well I think) is push most of the rectum out or your PTV thereby reducing the volume receiving RX dose. What is that volume correlated with? Late rectal toxicity. That’s it. If you think you are going to see some kind of benefit during OTVs then prepare for disappointment. I personally do like them for cases when there is substantial (long segment) abutment between the rectum and prostate. But universal use probably serves no meaningful purpose… even for SBRT.

 

[TheWallnerus]

If you think you are going to see some kind of benefit during OTVs then prepare for disappointment.

Isn't there data that acute toxicity correlates with late toxicity in prostate cancer RT. Will find later if I must!

 

[ramsesthenice]

Isn't there data that acute toxicity correlates with late toxicity in prostate cancer RT. Will find later if I must!

Yes but that assumes correlation. Typically if you have a high V70, you are almost guaranteed to also have a high V50, V40, etc. Thats the joy of a lot of these dosimetric studies. In general (for lots of disease sites), absolute volume receiving higher doses (for serial structures) corresponds better to risk of late toxicity than low-moderate dose bins. But since they are inherently correlated with one another, its a cloudy picture.

 

[TheWallnerus]

Yes but that assumes correlation. Typically if you have a high V70, you are almost guaranteed to also have a high V50, V40, etc. Thats the joy of a lot of these dosimetric studies. In general (for lots of disease sites), absolute volume receiving higher doses (for serial structures) corresponds better to risk of late toxicity than low-moderate dose bins. But since they are inherently correlated with one another, its a cloudy picture.

I haven’t had enough coffee or you missed my point. IIRC SpaceOAR has phIII evidence that it decreases late rectal toxicity. No need to invoke dosimetry per se. If there’s evidence that higher rates of acute side effects lead to more risk of late effects, it would have been my prediction that SpaceOAR users might have claimed noticing less acute effects (at OTVs). I have never injected the substance or treated anyone with it. But if SpaceOAR *never* affects acute *RT* toxicity then it is an intervention that can only give patients acute *global* toxicity.

 

[OTN]

I have not seen any data which has convinced me that the reduction of late GI toxicity with SpaceOAR > the complication rate of its placement.

 

[seper]

Yes but that assumes correlation. Typically if you have a high V70, you are almost guaranteed to also have a high V50, V40, etc. Thats the joy of a lot of these dosimetric studies. In general (for lots of disease sites), absolute volume receiving higher doses (for serial structures) corresponds better to risk of late toxicity than low-moderate dose bins. But since they are inherently correlated with one another, its a cloudy picture.

This correlation may be lost in "whole pelvis" RT. That was my question - how much better do the those plans look with SpaceOAR?

 

[ramsesthenice]

This correlation may be lost in "whole pelvis" RT. That was my question - how much better do the those plans look with SpaceOAR?

They look better in that the rectal V70 is better. But that is not the only thing that matters is it? Globally, the plans don't look that much better.

I have not seen any data which has convinced me that the reduction of late GI toxicity with SpaceOAR > the complication rate of its placement.

Thats the rub. Most patients don't get late toxicity. So most patients won't personally benefit from a rectal spacer. Our guys place a lot of them. In the last five years I have probably treated 50 patients or so with them. One had pain from rectal wall infiltration after the procedure and that was the only significant toxicity. No fistulas or ulcers etc. I can't recall any cases of GI bleeding in patients with a spacer. In the right situation it probably has a net benefit. But its not a huge benefit and the equation can quickly change with user experience, patient selection etc. Its not a game changer by any means and universal placement is probably inappropriate.

 

[Ray D. Ayshun]

I have not seen any data which has convinced me that the reduction of late GI toxicity with SpaceOAR > the complication rate of its placement.

Why has nobody looked to see if there's a correlation between the SpaceOAR procedural code and PTSD diagnostic code?

 

[elementaryschooleconomics]

Why has nobody looked to see if there's a correlation between the SpaceOAR procedural code and PTSD diagnostic code?

For the patient or the RadOnc treating him?

 

[Mandelin Rain]

For the patient or the RadOnc treating him?

Depends on if it was reimbursed or not.

 

[Radonky]

FWIW, if you drink the SpaceOAR history koolaid, and there may be some merit to it, the original spaceOAR placement was not done optimally. They allowed any type of ultrasound guidance, i.e., without a stepper and without 2 planes of view. So you had people who angled the probe superiorly against the wall of the rectum to view the prostate, compressing the perirectal fat between the prostate and rectum, making it easier to puncture and insert gel into the rectum.

My sweet spaceOAR rep, after cautiously advancing another goblet of koolaid, suggested that since they made changes to required equipment and now have more experienced staff, the rates of serious adverse events (fistula, ulcerations et al.) are very, very rare.