@ozelli
I don' think you are wrong in your opinion.
What my R/O at UFHPTI said to me (he has been doing proton radiation treatments for 20 years) is that everyone bodies are different. Bike riding might not affect the prostate on one person but may on another.

No one's body is exactly like another. How big the prostate is, it's location, fat, muscle, buttocks, bones, they are all different. I was told my prostate would move around if I moved during treatments and they make a specific bed for you to lay in to keep you from moving.

I had gas one day and had to go through a lot more xray and moving me around as gas in my colon was moving prostate. So to think a bike seat digging into your bottom for long times and motion back and forth would not affect prostate in some.

UFHPTI was huge on research. They just got another 25 million dollar federal grant to do long term study of radiation treatments for prostate cancer.

One of the research UFHPTI showed was taking cell protection supplements prior, during and after treatments. It was supplements that are considered oxidation protection, protection of cells, etc. My R/O said one study showed no correlation to protecting cancer cells the other study showed a correlation as would protect cancer cells as well.

UHFPTI aired on the side of saying if it was possible taking supplements could affect radiation treatments success. I am a supplement freak. I had about 6 different supplements I was told not to take. Most radiation treatments are to damage the cells of the PC. Normal cells of the prostate can repair themselves. The PC cancer cannot after damaged and eventually die.

I think the bike riding is a personal thing and personal decision as you know your own personal body make up and how bike riding makes you feel. I know many bike riders who have no issues with pain, discomfort, from race bike seats and others (like me) drives my bottom crazy with a lot of pain.

My PCP a long time ago asked me to refrain from bike riding prior to my PSA tests. As I mentioned I usually ride 20 miles and if I can do something to get a more accurate PSA test for me I chose to follow the advice.