This plot shows the Biochemical Relapse Free Survival after RT and ADT, after 10 years , for Intermediate and High Risk men, comparing different levels of testosterone nadir ( 50 nd/dL). (ref: 2019)
The best outcomes are significantly associated with a lower testosterone nadir ( < 20 ng/dL), and the relationship appears to be roughly linear; heading toward a 100 % survival rate for a testosterone nadir = 0.
This may be well-known to many of you, but it was new to me.
The prior definition of castration being < 50 ng/dL probably needs to redefined to < 20 ng/dL. (I read that the level of 50 ng/dL may be an artifact representing the lowest limit that testosterone could be accurately measured many years ago. That makes sense to me).