The inherent limitations of PSA and conventional imaging including CT and bone scan for determining treatment response are well known and together with the capability of PSMA PET to better identify presence, sites, and burden of metastatic tumor in CRPC, this discrepancy opens up opportunities for potentially better response assessment that may result in better therapeutic planning (continuing, changing, or adding type of therapies) with the hopes of achieving better survival. The gene discussed is KLK3; the disease is metastatic neoplasm.