Prostate-specific membrane antigen is a biomarker for residual disease following neoadjuvant intense androgen deprivation therapy in prostate cancer

Neoadjuvant intense androgen deprivation therapy can exert a wide range of histologic responses, which in turn are reflected in the final prostatectomy specimen. Accurate identification and measurement of residual tumor volumes are critical for tracking and stratifying patient outcomes. The goal of this current study was to evaluate the ability of antibodies against prostate-specific membrane antigen (PSMA) to detect residual tumor in a cohort of 35 patients treated with androgen deprivation therapy plus enzalutamide for six months prior to radical prostatectomy. Residual carcinoma was detected in 31 patients, and PSMA reacted positively with tumor in all cases. PSMA staining was 95.5% sensitive for tumor, with approximately 81.6% of benign regions showing no reactivity. By contrast, PSMA positively reacted with 72.2% of benign regions in a control cohort of 37 untreated cases, resulting in 27.8% specificity for tumor. PSMA further identified highly dedifferentiated prostate carcinomas including tumors with evidence of neuroendocrine differentiation. We propose that anti-PSMA immunostaining be a standardized marker for identifying residual cancer in the setting of neoadjuvant intense androgen deprivation therapy.