Hi - I did 33 days of radiation combined with hormone therapy a year ago and did not find that I had any additional gas. This was a second coming of PC after 5 years of remission after the initial surgery, so if you are not in that phase, then my experience may not have been equivalent. I empathize with you because every day the radiologists would ask if I had gas! Kind of embarrassing when they are all women, you have it, and it blocks the area they are going to radiate. They sent me back out a couple of times to work up a fart to clear the area!
Good luck with your