For advanced and metastatic prostate cancer, analysis of circulating tumor cells and circulating mRNA (e.g., ARV7 mRNA) as well as gene mutation testing (e.g., BRCA1 and BRCA2) can help predict treatment response, particularly for second-generation antiandrogens and PARP inhibitors, and provide valuable prognostic insights. This evidence concerns the gene BRCA1 and metastatic prostate carcinoma.