The hormone therapy will temporarily lower PSA anyway, so it won't be until he finishes HT and testosterone returns that you will have a good idea how the RT went. They probably will measure PSA every 3 or 6 months before then, but it's not very meaningful.
Those first 2 appointments after the RT are really for him to flag up any issues he wants addressing. They aren't going to be able to say much about the outcome so early. If there is any support you need such as access to ED clinic, that is the opportunity to ask for it, e.g. might want to ask for Tadalafil and a pump.