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.
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.
It's the risk/benefit ratio.
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.
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.
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.
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.
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.
For the patient or the RadOnc treating him?
Depends on if it was reimbursed or not.
