Hi there. Even though my RO used SBRT (TrueBeam STX) for a five fraction course, he indicated that even with SpaceOar to protect the bowel diarrhea was a possibility espcially since they also advised a low fiber diet during treatment to keep the bowels "less active" or something to that effect. In any case, I did have some minor diarrhea which I addressed with Pepto Bismol or Imodium, and drinking a lot of water. After a month + since I finished treatment everything is back to normal. Best of luck to you.