Hi @cpalmer, Mayo Clinic Connect is a network of patients and therefore not the right space to seek a diagnosis. But we can perhaps give you ideas about avenues to pursue to find answers. To help with this, I've added your question to the Digestive Health group and the Spine Health group.
It sounds like you're still in the dark to the underlying cause. Side effects of SBRT are similar to those of other types of radiation treatment for prostate cancer, such as urinary problems, rectal irritation, erectile dysfunction, and fatigue. But these side effects are usually temporary.
Did you have rectal irritation after the cyberknife treatments? Was your spinal surgery an attempt to relief the pain issues?