Also a cyclist. Had SBRT and 6 months of ADT two years ago. Prostate was sensitive for awhile so needed padded underwear in addition to padded shorts for biking. ADT side effects for me were mostly mental (bad depression), though my testosterone took an exceptionally long time to reach low normal (18 months) and I lost a bit of stamina and developed some osteoporosis.

Side effects of SBRT were tiredness and burning urination for about 1-2 months afterwards, then nothing. A few months ago developed radiation cystitis that's being controlled with meds. Had no bowel problems during or after treatment. Never had ED even while on ADT, though ADT did cause some anorgasmia that's now resolved. Am back to cycling like before, though did buy a wider seat.