A perplexing situation is what to do after one has tried one or more potentially curative therapies (e.g., prostatectomy plus salvage radiation including pelvic lymph nodes), and there are no detectable metastases, but PSA keeps rising. The TOAD randomized clinical trial demonstrated that survival is improved by starting on hormone therapy (intermittent or continuous) as soon as recurrence is observed. Chemo has not proved to increase survival until after multiple metastases are detected (CHAARTED). Waiting for metastases to appear and spot treating them has not proved to be beneficial either (see this link).
There may be hope in participating in clinical trials. There aren't many. There is a trial for the earlier use of Xtandi therapies, as well as trials for novel therapeutics, like apalutamide and Prostvac, which have been very promising in early trials. Here's a current list that you may wish to discuss with your medical oncologist:
Advanced hormonal therapies:
Apalutamide:at University of Texas, Houston (a larger trial is no longer recruiting)
Apalutamide/ degarelix/abiraterone at 8 locations
Xtandi at 172 locations
Xtandi at University of Colorado, Denver
Prostvac at NIH
Durvalumab + Olaparib at MSK
Olaparib - recurrent - Johns Hopkins & Thomas Jefferson U.
Phenelzine at USC