Treatments and diagnostics for treatment efficacy against solid and liquid cancers are described. The treatments utilize a combination therapy of Galeterone and a proteasome inhibitor. The diagnostics can measure androgen receptor (AR) cleavage products including AR-variant 7 (AR-V7) cleavage products, Poly (ADP-ribose) polymerase (PARP) cleavage products, and/or Spectrin α2 cleavage products or inhibition of DUB activities from a blood sample to monitor treatment efficacy for castration-resistant prostate cancer (CRPC) or multiple myeloma (MM).