Immunohistochemical Analysis of Androgen Receptor Expression Predicts the Prognosis of Metastatic Castration-Sensitive Prostate Cancer Patients Receiving Abiraterone Acetate.

BACKGROUND: The efficacy of abiraterone acetate varies among patients with high-risk metastatic castration-sensitive prostate cancer (mCSPC). Both androgen receptor (AR) and cytokeratin 18 (CK18) are markers of the luminal lineage of prostate cancer, and their expression levels have been suggested to affect the response to androgen deprivation therapy (ADT). This study aimed to predict the efficacy of abiraterone acetate in high-risk mCSPC via immunohistochemical staining of biopsy specimens obtained at the time of prostate cancer diagnosis. METHODS: We retrospectively analyzed 44 patients treated with abiraterone acetate in combination with ADT. AR and CK18 expression in prostate biopsy specimens were assessed using immunohistochemical staining. RESULTS: AR and CK18 staining was not significantly associated with overall survival (OS). However, low AR staining was significantly associated with a shorter time to castration-resistant prostate cancer (TTCRPC) compared with high AR staining (log-rank test, p = 0.018). Similarly, low CK18 staining was significantly associated with a shorter TTCRPC compared with high CK18 staining (log-rank test, p = 0.037). CONCLUSIONS: Immunohistochemical analysis of AR or CK18 expression in biopsy specimens may serve as a predictive biomarker of high-risk mCSPC treated with abiraterone acetate. TRIAL REGISTRATION: None.