This invention relates to the treatment of breast cancer in a subject, for example a female subject. Including methods of: treating metastatic breast cancer; refractory breast cancer; AR-positive breast cancer; AR-positive refractory breast cancer; AR-positive metastatic breast cancer; AR-positive and ER-positive breast cancer; triple negative breast cancer; advanced breast cancer; breast cancer that has failed selective estrogen receptor modulator (SERM) (tamoxifen, toremifene, raloxifene), gonadotropin-releasing hormone (GnRH) agonist (goserelin), aromatase inhibitor (AI) (letrozole, anastrozole, exemestane), cyclin-dependent kinase 4 / 6 (CDK 4 / 6) inhibitor (palbociclib (Ibrance), ribociclib (Kisqali), abemaciclib (Vorzenio)), mTOR inhibitor (everolimus), trastuzumab (Herceptin, ado-trastuzumab emtansine), pertuzumab (Perjeta), lapatinib, neratinib (Nerlynx), olaparib (Lynparza) (an inhibitor of the enzyme poly ADP ribose polymerase (PARP)), bevacizumab (Avastin), and / or fulvestrant treatments; metastasis in a subject suffering from breast cancer; HER2-positive; treating a subject suffering from ER mutant expressing breast cancer and / or treating breast cancer in a subject, by first determining the 18F-16β-fluoro-5α-dihydrotestosterone (18F-DHT) tumor uptake and identifying said subject as having AR-positive breast cancer based on 18F-DHT tumor uptake, comprising administering to the subject a therapeutically effective amount of a selective androgen receptor modulator (SARM) compound.