I think chemo with the up-front "triple treatment" for stage 4 is used only if there are lots of metastases and/or the cancer has become castrate-resistant.

For castrate-sensitive oligometastatic prostate cancer, I don't think chemo would make sense at the start (radiation + ADT + an androgen-reception inhibitor like Apalutamide get the job done), but interested to hear from anyone who's seen otherwise.