Detection of prostatic cells in peripheral blood: correlation with serum concentrations of prostate-specific antigen

We have studied the expression of prostate-specific antigen (PSA) mRNA by reverse transcriptase-polymerase chain reaction in peripheral blood of 25 patients with cancer of the prostate (CAP), four with benign prostatic hyperplasia (BPH), two with renal stones, three with other types of cancer, and six healthy male and three female controls. Expression of mRNA specific for a certain tissue in peripheral blood is thought to indicate the presence of circulating cancer cells and metastatic spread of a tumor originating from this tissue. We detected PSA mRNA in 9 of 18 CAP patients with metastatic disease but in none of 7 patients without metastases. Negative results in patients with metastatic disease were associated with successful endocrine therapy and low concentrations of serum PSA, and the correlation between serum concentrations of PSA and the presence of PSA mRNA in peripheral blood was statistically significant. PSA mRNA was not found in patients with BPH, other types of cancer, or in healthy controls. Thus the occurrence of PSA mRNA in peripheral blood is associated with metastatic CAP.