Attached is a discussion on rectal bleeding and proton therapy. I can tell you that I was advised after my 28 session treatment that bleeding occurs in 30% of patients, then told 5% then told between 5-30% . Space oar will dramatically reduce that occurrence, I think it is still higher than other forms of radiation and that there is little margin for error. I believe error occurs with gel placement more often than some would suggest. I have had some bleeding shortly after treatment and one incident 11 months out along with digestive track issues. I do worry that bleeding would equate to proctitis ( chronic at some point ). Bleeding can occur with any form of radiation but it seems more prevalent in Proton. Just my opinion not a medical professional. I think based on my reading MRI guided SBRT seems to be a solid alternative.