This is an interesting thread and I have not had androgen deprivation therapy [ADT.] (So far, anyway--my time may come.) But here is my understanding: Most, but not all prostate cancer [PC] is stimulated by androgen hormones. (Testosterone is an androgen hormone.) PC that is not suppressed by ADT is called "castration resistant"--the castration being referred to is ADT, sometimes called biochemical castration.
The reason for taking ADT together with radiation is that they believe the suppressed cancer is more responsive to killing by radiation. Because most if not all men really dislike ADT, a major focus of study has been how to minimize the need for ADT in treatment protocols. However, it's hard to study because the results are evident over a number of years, not a number of months. This is true for a lot of aspects of PC diagnosis and treatment. It's also true that men in their 60s (when PC is most often diagnosed and treated) may have issues with sexual function even when PC is not a factor. A PC diagnosis doesn't seem to change this.
While ADT has been tried as a treatment for PC without radiation or surgery, this is not a current standard of care so far as I know. (Someone I know chose this as a treatment.)
My understanding is that if PC progresses, eventually it [maybe? often? always?] becomes "castration resistant." This also is a concern in medically recommended courses of treatment.
Since all PC treatments affect health-related quality of life [HRQOL], treatment protocols often involve tradeoffs. The big PC HRQOL issues are bowels, urine, and sexual function. The general consensus is that surgery* has a quicker, but less progressive impact while radiation has a slower, but more progressive impact on HRQOL. Of course, some of us get to experience surgery, radiation and ADT, and the disease still progresses.
*Also, some immediate HRQOL issues after surgery are from the abdominal surgery itself, and those can improve for up to two years before we actually reach our post-surgical baseline. The surgery I'm talking about is radical prostatectomy [RP], either open or laparoscopic [LRP], and if laparoscopic, typically robot-assisted [RALP].
So, I am grateful for the health I do enjoy, yet aware that even that is not a guarantee for the future.