My father has been on Zytiga and Lupron since May 2018 and his PSA has slowly dropped from 42 to 9.5 but has now been around 9.5 for the past couple of tests (aprox for a month). He had his prostate removed in January but unfortunately his PET PSMA showed multiple mets shortly after. His doctor says that as long as his PSA isn't rising, they won't change his treatment but I thought that the goal was to lower the PSA to undetectable levels and 9.5 seems fairly high. Does this mean that 9.5 is his PSA nadir or is it possible that his PSA will continue to lower? If it is his nadir, is it worth changing his treatment? Does this fairly high nadir have any significance in terms of OS? He Gleason is 8 (4+4) and is 72 yo. He had bad side effects from the Zytiga so they had to take him off/on a couple of times and change the dosage so he's only been back on the full dose for about a month.
Thanks so much