Peripheral blood reverse transcription PCR assay for prostate stem cell antigen correlates with androgen-independent progression in advanced prostate cancer.

Recent studies show that prostate stem cell antigen (PSCA) mRNA positivity in peripheral blood correlates with disease progression in prostate cancer (PCa). Our study is to evaluate the association between peripheral blood PSCA status and androgen-independent progression (AIP) in a cohort of patients with advanced PCa under androgen deprivation therapy (ADT). PSCA mRNA was measured by reverse transcriptase polymerase chain reaction (RT-PCR) assay in peripheral blood samples from 116 patients with locally advanced or metastatic PCa who were treated with primary ADT and from 40 healthy controls. The Kaplan-Meier and the Cox proportional hazards methods were used to assess potential predictors of AIP. Pretreatment RT-PCR-PSCA was positive in 37 (31.9%) of 116 patients. All healthy volunteers were negative for PSCA mRNA. Although seven (14.9%) of 47 patients with Gleason score ≤7 were PSCA positive, 30 (43.5%) of 69 patients with Gleason score >7 were PSCA positive (p = 0.016). PSCA mRNA was detected in 28 (58.3%) of 48 patients with metastatic PCa, compared to nine (13.2%) of 68 patients with locally advanced disease (p = 0.012). AIP developed in 59 (50.9%) patients during a median follow-up period of 35.4 months (range: 4-78 months). Patients with PSCA negativity experienced significantly longer remissions compared to those with PSCA positivity (log-rank test: p < 0.001). Multivariate Cox regression analysis further demonstrated that PSCA positivity had a significantly increased risk of AIP (HR = 4.303, 95% CI: 3.761-7.482, p < 0.001). Pretreatment RT-PCR PSCA positivity in peripheral blood independently signals the presence of AIP in patients with advanced PCa treated with ADT.