@scottbeammeup (I think this is a star wars connection)
Your R/O and urologist should have been talking to you about side affects from radiation. You had SBRT which I believe is photon radiation. It is different than proton as the radiation continues to go out through your body and does not stop at prostate and margins set like proton does.

YES, YES, riding a bike (regardless of padding) should have been told to you will cause irritation to your prostate. I was told to stop riding my bike 2 weeks prior to radiation, no riding during, and refrain from riding it for 1 month after. I wear padded shorts but the weight and seat will irriate your prostate. Were you not told about the direct connection to higher PSA numbers a possibility of bike riding. I had to stop bike riding prior to my PSA test to make sure that was not the cause of my rising PSA numbers (it was cancer though).

When you have radiation your prostate has gone through a war. It is trying to heal and recover but radiation has made in extremely irritated. When you add anymore irritation to it you are going to feel it and going to have additional side affects. Irritated your prostate after the radiation war is just going to make is worse and slow the healing process.

I am really wondering where you had your treatments done. All of your questions should have been gone over with your prior to your treatments of what to expect and what to do to minimize them prior, during and after.

Everyone is different and will react different to the radiation treatments. Some have none, some minor and some really bad. If you read MCC you will see that most have an increase in need to urinate and changes in velocity etc. So you are experiencing what most do. Yes it does improve (for most) over time but stay away from anything that will irritate your prostate (no biking).

I was about 3 weeks into my radiation (had proton) when the urge to urinate went up and the ability to hold it without leaking started. At UFHPTI we had to drink a certain amount of water prior to radiation. That meant after radiation treatment I better go to bathroom regardless of feeling the need to as the drive home it would come on with great urgency. I also urinated about every 2 hours including getting up at night.

About 4 weeks after radiation ended my urge to urinate and velocity of stream started to improve. Now over a year since radiation is back to the way it was. That does not mean I don't get up several times a night but that was the norm for me. I drink to much liquid prior to going to bed.

Again when I read posts like this about side affects and questions on biking I really feel bad for the individual as these side affects should have been discussed with you especially the bike riding and the increase in need to urinate.