@jaygk (I had 28 fractions of proton radiation + 6 months of ADT.) My medical oncologist advised me about low libido and ED during radiation treatments, that the key is to continue doing it, despite the “want to” not being there.

Also, perhaps by ramping up my resistance-training and cardio programs to minimize the side-effects of ADT, that might(??) also have had the side-benefit of keeping the blood flowing “down there” as well; I don’t know. Much of what goes on “down there” is about hydraulics so, keeping the blood flowing would seem to be important.

So, I didn’t take the cialis-type medication to promote blood flow; just kept exercising, cardio, and kept doing it.
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Another thing to remember is to avoid radiation to the penile bulb —> https://www.icr.ac.uk/news-archive/avoiding-penile-bulb-with-radiotherapy-could-save-men-with-prostate-cancer-from-harmful-side-effects

@jaygk The important aspect of this therapy is to continue to get erections. If you are still getting nighttime erection and are sexually active it probably does not matter. However, Tadalafil 5mg (generic) is cheap and it will not hurt. As long as you are getting erections it does not matter that you did not start this before IMRT. It will be most effective for those that also have ADT and no erections since that will be for 6 months to 2 years. Most radiation ED is caused by vascular damage. That can cause nerve damage due to lack of nutrition and/or fibrosis of the spongy erectile tissue. Scholtz stated that there is no age adjusted increase in ED of patients with prostate radiation after the first 2 years post-treatment. It should not surprise anyone that 80 year old radiation prostate patients have more ED than 60 year old patients that had nerve sparing RT.

To answer your questions: 1) Yes 2) None after ADT ended. I cannot say the Tadalafil worked, but more importantly I cannot say it did not work. Someone tried a study, but it was flawed. There are both ethical and compliance concerns with any randomized study. Would you want to be in the placebo group? If you have ever taken any PDE5 pill you will know if you have the real thing so there is no blind patient group. I just considered this protocol cheap insurance. If not covered by your insurance cash pay from AARP mail (must be member) is $6.36 for 90 days ship included. For 360 days it is $23 from Mark Cuban's Cost Plus ($11 is flat fill & ship so more expensive with short prescriptions).