Unlike hormonal therapy, the radiation itself typically has few side-effects aside of during the sessions, so only for a few weeks. Those are most often extra fatigue (though not as pronounced as the one caused by ADT/Hormone therapy) and a more pressing urge to go the toilet.
Symptoms like hot flashes and mood swings are associated with the ADT and will vary from men to men and also across different drugs. I can't recommend any as having less side-effect than others because what is true for me might not be true for you. But part of the hot flashed and mood swings comes from how out of balance your hormones get when you block off testosterone. Its basically near-instant andropause/menopause. I find that Norwegian Kelp, which is a supplement available over the counter and even on Amazon, has helped me with hot flashes quite rapidly, after only 3-4 days of using them. My wife and sister, both going through menopause, have both felt relief too when they tried it.
Best of luck to you!