Have you had a PSMA PET scan to see if your cancer has spread outside the prostate? That is what can cause your PSA to rise so much. SBRT on metastasis found could reduce your PSA. If your cancer has spread only/mainly to the bone, then radium-223 Could also be useful as well.

Pluvicto is also a next step To try. You should be aware that is only really successful in 1/3 of the cases somewhat successful in 1/3 and not successful at all in 1/3.

One thing you could try is switching from Nubeqa to Zytiga. It may not be successful, but it could be worth a try.