Objectives: Detection of circulating tumor cells may improve the preoperative local staging of prostate cancers. The aim of this study was to perform enhanced reverse transcriptase-polymerase chain reaction (RT-PCR) of prostate-specific antigen (PSA) mRNA to define the predictive value of PSA-positive circulating cells in a large series of patients.
Methods: The study included 46 patients with Stage T1 to T2 prostate cancer, 94 with benign prostatic hyperplasia (BPH), and 51 (including 9 women) with nonprostatic disease. PSA-positive cells from peripheral blood samples were detected by Southern blot analysis of the RT-PCR products. Original oligonucleotide primers were defined to exclusively detect the three PSA mRNA splices.
Results: Circulating PSA-positive cells were observed in 8 (8.5%) of 94 patients with BPH, 10 (22%) of 46 with Stage T1 to T2 prostate cancer, and 9 (17.6%) of 51 with nonprostatic disease. The detection rate of PSA-positive circulating cells was significantly increased in patients with prostate cancer versus patients with BPH (P = 0.03). Among clinically localized prostate cancers with a Gleason score less than 8, a correlation was observed between PSA-positive circulating cells and Stage pT3 cancer (P = 0.038), capsular penetration (P = 0.04), and a positive margin (P = 0.038). The specificity of the assay for Stage pT3 cancer detection was 84.6%, with a positive predictive value of 60%.
Conclusions: Although RT-PCR assay may have a role in preoperative local staging, this study demonstrated the absence of tissue and tumor specificity of PSA-positive circulating cells, accounting for the weak positive predictive value of this technique.