@diverjer Yes - The use of endorectal balloons was common for primary radiation treatments prior to 2015 (when the SpaceOAR Hydrogel rectal spacer was approved for use).

They found that SpaceOAR offered improved benefits when compared to the older endorectal balloons: https://www.urologytimes.com/view/hydrogel-spacer-lowers-rectal-bleeding-vs-balloon-immobilization-treatment

The problem with using endorectal balloons for primary radiation treatments is that the anterior wall of the rectum is left fully exposed to radiation; in addition, the balloon has to be inserted and then removed at each treatment. (Sounds pleasant doesn’t it?) Whereas the rectal spacer is injected just once, and lasts beyond the entire course of treatments.

All that is the same for salvage radiation treatments (which can be post-prostatectomy or post-primary radiation).

Though uncommon, there have been a few studies regarding the use of rectal spacers for salvage radiation post-prostatectomy:
> This from a 2024 paper: https://www.mdpi.com/2563-6499/5/2/20

> this from a 2015 paper: https://pubmed.ncbi.nlm.nih.gov/25339311/

> this from a 2019 paper: https://medcraveonline.com/IJRRT/IJRRT-06-00224.pdf

If I were looking into salvage radiation post-prostatectomy, I would at least ask about endorectal balloons (& possibly about using a rectal spacer).