I had the SpaceOAR spacer, but it hasn't been completely effective.
In their studies, it had no significant effect on grade 2 or higher acute rectal symptoms - the ones you experience between 1 to 3 months after treatment. They found that it lessened the incidence of late term rectal symptoms - the ones you may experience 6 months to 2 years from treatment. But late term rectal symptoms are seldom a problem. I call it an expensive solution in search of a problem.
They make claims that are implausible to me.