One of the topics that frequently gets discussed on this forum is the side effects of radiation vs. the side effects of surgery.

In the interest of adding a little "balance" to the discussion, I offer the following quotes from Dr. Dattoli's book, The Dattoli Blue Ribbon Prostate Cancer Solution, How to Survive and Thrive Without Surgery:

EBRT

"Although most men retain erectile function after the conclusion of radiation therapy, as many as half of the men who undergo conventional EBRT will eventually develop erectile dysfunction." Page 79

Seeds

"Generally speaking, patients having prostate brachytherapy will have erectile dysfunction in about 15% to 20% of cases, although some institutions are reporting higher rates of incidence. Brachytherapy does not appear to produce the steady decline of potency that we have seen with full course external beam radiation through the years. Rather, I have noted not only a leveling off of the potency rate over time after implantation, but even a gradual improvement over time. Essentially where you will be at two to three years after treatment is where you will likely be as far as erectile function.... Page 116

On a more positive note, Dattoli has also said (elsewhere):

"For those men who do experience difficulties with potency following treatment, intracavernosal paparavine, PGE1 injections and oral erectile aids including Viagra, Levitra and Cialis are very effective. For those men who are potent at the time of treatment, 92% of patients having brachytherapy without or without supplemental external radiation will maintain their potency with the aid of one of these medications."

I've had some ED post RT, but 20mg of sildenafil and game's on.