I had dry orgasms after HD brachytherapy, but they eventually went away. Unfortunately, it's because everything went away (completely impotent now five years out). IMHO the orgasm sensation was exactly the same whether anything came out or not. I wouldn't have even noticed if I hadn't *********d once and seen it.
I had this conversion with a friend who was diagnosed with prostate cancer. His biopsy was nearly identical to mine, including which cores were positive, 3+4, etc. This was maybe one year after I was treated, so I was still functional. When I told him everything worked and felt the same, but nothing came out, he took it really hard. I thought what I told him would reassure him, but it had the opposite effect. Three years later he's still doing active surveillance by getting an MRI every six months. I'm not even sure this is a valid way of doing surveillance. He's terrified of losing functionality.
For me, dry O's were no big deal. I don't understand the reaction myself, but I've never been a fan of oral sex, so there was no way either myself or my wife knew anything was different about
my orgasms until I whacked off in the bathroom