I too have been on Tamsulosin since my radiotherapy two and a half years ago, and I'll probably be on it for the rest of my life. As someone's already mentioned, the main side-effect of it is that it lowers your blood pressure.
By the way, it's advisable to create your own thread to ask a question, rather than hijacking someone else's. Admittedly in this case that doesn't matter because the original poster hasn't been back since 2017, but do start your own threads in the future!
Best wishes,
Chris