I'm on Zytiga Prednisoneand Lupron( 6 weeks). Doc says 2 yrs. duration . My psa is already close to undetectable . I was hoping to have Doc declare REMISSION next year and allow me to take a break and let the body recover from zytiga and Prednisone and lupron side effects.
I am surprised by 4 yrs of treatment. There are some studies showing a build up of resistance to Zytiga and Lupron. This allows PC cells to start dividing and growing into tumors. This maybe what is going on in your situation.
I fully expect that my prostate cancer will regenerate at some point. My hope is to have remission provide some quality time before recurrence.
Good Luck