@rleech No apologies ever needed. I respect the journey that you and your husband are undergoing.

There are more knowledgeable people in this forum and Mayo Clinic about immunotherapies, but I can offer from my experience that best practices include blood monitoring (PSA and in the UK, PSE), PSMA PET scans, and immune cell ( T-cell, B-cell, etc) monitoring , along with usual other blood markers to ensure that the immune system is positively responding to treatment. It is important with any immunotherapy to monitor the overall immune system’s response and your medical oncologist will know the tests required in order to achieve that objective.

Peptide based immunotherapies are not new, although not common for prostate cancer, and require characterizing the existing PCa mutations.

The UK has several advanced research laboratories specialized in PCa immunotherapy development. I encourage UK patients who have exhausted standard of care treatments to consider UK based clinical trials specific to PCa that require germline and somatic tests in advance. In particular, the PCa immunotherapy research teams are a great source of information on all previously attempted PCa immunotherapies. They develop a deep understanding of what has been effective and what is not effective, and why.

Best wishes.