astonishingurs
Your oncologist/radiologist or urologist should be giving diet recommendations and restrictions. UFPTI gave a handout on the diet to use and was high protein and to avoid foods that cause gas like beans and other things that cause it (like soy).

This is to keep gas out of the rectum area that can push (the gas) up against rectum which can move the prostrate from oringinal mapping.

Does it happen, YES! I was careful but one day took a protein powder. The next day at radiation treatment I could feel some gas and sure enough techs came back and said could see gas in rectum and was affecting the prostrate as it had moved.

I was not eating anything outside the diet recommenations so I checked the protein powder. It was made with soy protein. My techs next time I came yes most definitely that was the cause.