Predictive effect of androgen receptor splice variant 7 expression on time to castration resistance in patients with metastatic prostate cancer

Abstract

Objective To investigate the predictive effect of androgen receptor splice variant 7 (AR-V7) expression on time to castration resistance in patients with metastatic prostate cancer.Methods The data of 113 cases of advanced metastatic prostate cancer diagnosed by prostate biopsy in our institute from Jan.2002 to Jun.2010 were collected retrospectively.The median age at diagnosis was 70 years,ranged from 43 to 84 years.The median tPSA was 120.0 μg/L,ranged from 3.0 to 6 006.2 μg/L.There were 5 patients in M1a(4.4％),94 patients in M1b(83.2％) and 14 patients in M1c(12.4％).All patients received hormonal therapy.1mmunohistochemical staining and AR-V7 specific antibody were used to detect the expression of AR-V7 in prostate cancer tissues.Cox regression models were used to analyze the predictive role of patient characteristics including patient's age at diagnosis,tPSA level at diagnosis,Gleason score,clinical stage,PSA nadir during hormonal therapy,the time to PSA nadir and PSA half-life.The effect of AR-V7 expression on time to castration resistance was analyzed using Kaplan-Meier curves,and the differences were assessed using the log-rank test.Results The PSA nadir ranged from 0.0 to 143.0 μg/L and the median value was 0.7 μg/L.The time to PSA nadir ranged from 0.9 to 71.0 months and the median value was 8.1 months.The median PSA half life was 1.0 month,which ranged from 0.1 to 41.0 months.Followed up for a median time of 27 months,100 patients progressed to castration-resistant prostate cancer (CRPC) and the median time to castration resistance was 24 months.The expression of AR-V7 was positive in 23 out of 113 patients.Multivariate analysis showed that the expression of AR-V7 in prostate cancer (P=0.004,HR =2.223) and PSA nadir during hormonal therapy (P =0.035,HR =1.011) were independent predictive factors of time to castration resistance.The median time to castration resistance for patients with and without AR-V7 expression were (16.04±3.4) months and (30.04-6.0) months,respectively (P=0.001).Conclusions The expression of AR-V7 in prostate cancer and PSA nadir during hormonal therapy are independent predictive factors of time to castration resistance.The AR-V7 could be a potential therapeutic target for advanced prostate cancer. Key words: Prostatic neoplasms; Hormonal therapy; Time to castration resistance; Androgen receptor splice variant 7; PSA nadir