How do you treat a patient who develops metastatic prostate CA while on enzalutamide or apalutamide for originally M0 CRPC?

Most patients in this setting actually have mCRPC but very low volume disease. Occasionally this can be local/regional only but most PET imaging studies suggest that M0 CRPC is comprised of metastatic disease below the limits of detection of conventional CT and bone scan imaging. Thus I manage these patients post AR therapy similarly to M1 patients by performing imaging (PET if available such as Axumin or PSMA or NaF), I offer clinical trials where available, and progress through standard options including sipuleucel T, consideration of AR-V7 testing for abiraterone subsequent use, or a trial of abiraterone with close follow up. Docetaxel and radium are generally reserved for clear and more rapid/aggressive mCRPC progression. Cross resistance between AR inhibitors in this setting is the major unmet medical need.