@erbill
I did not have cyberknife sbrt.
I had 30 rounds of proton radiation. I had 4 gold markers used to set up my treatment each time. And yes a couple of times adjustments had to be made on my simulation bed to re-align me. I had gas one time in rectum that was moving prostate around. I did have the Space Oar to move rectum away from prostate and drank water prior to treatments to move bladder away from prostate.

Regarding margins. Your R/O decides where your margins are. My R/O at UFHTPI has a physics department that assists with treatments set up and specific programming. My R/O stated he treats the entire prostate and margins. He explained that prostate cancer can be in areas at cellular level and those wanted to make sure he treats all prostate and margins.

The margins are set up by your R/O based on his or her findings, biopsies, MRIs, CTs, and as a safeguard.

How hard would it be for you to go to a facility that has the S7 model? If I had an option, I would go to a facility with the most upgraded and new type of radiation treatment possible if you are going to just consider cyberknife only.

Have you considered getting a second opinion on your diagnosis and treatment options? I chose UFHPTI as they had proton radiation and had the latest upgrades and newest proton equipment and gantries. I declined going to Mayo Jacksonville as only had photon (building new cancer center with proton and will open in 2026).