Resistance to Androgen-Pathway Drugs in Prostate Cancer

To the Editor: Antonarakis and colleagues (Sept. 11 issue) 1 reported a significant association between the presence of androgen-receptor splice variant 7 messenger RNA (AR-V7) in circulating tumor cells and shorter prostate-specific antigen (PSA) progression–free survival, clinical or radiographic progression–free survival, and overall survival in men with metastatic castration-resistant prostate cancer who were treated with enzalutamide or abiraterone. Several treatment options (abiraterone, enzalutamide, sipuleucel-T, and radium-223) have recently been shown to prolong survival in men with metastatic castration-resistant prostate cancer who have not previously been treated with chemotherapy; the identification of reliable biomarkers that can predict response should optimize treatment with . . .