Hello Sofiejoan
You're profile doesn't give any details of PSA, Gleason etc so it isn't easy to offer advice
All I can add is that at around 72 on diagnosis, a year on active surveillance and then low dose seed Brachytherapy at 73/4 my husband had his 1st Anniversary of the implant in June this year and his PSA was down to 0.5 from 6.3 at its highest.
He had his 75th birthday last Tuesday and there have been very few long lasting side effects.
That's not to say they won't happen further down the line, especially with the bowel but that is something that has to be put up with if it happens in order to gain the years in between.
Good luck with your choice