Steve-
Here's the MSKCC study using Viagra:
www.jurology.com/article/S0022-5347(14)00355-3/abstract(note that after 2 years, there was no difference - but the dropout rate was high and the men were older)
Here's the Mayo study on Cialis:
jamanetwork.com/journals/jama/fullarticle/1853160But there were reservations raised about
it:
jamanetwork.com/journals/jama/article-abstract/1896972Here's an uncontrolled MD Anderson study using Cialis on guys having brachytherapy:
www.brachyjournal.com/article/S1538-4721(14)00634-5/fulltextSo the data are not convincing for the use of any ED meds after radiation. I used it (low dose Viagra) anyway. (If nothing else, these ED meds improve urine flow.) The goal is to prevent fibrosis in the blood vessels. It's probably true that daily orgasms may accomplish the same benefit.