MOLECULAR STAGING OF PROSTATE-CANCER WITH THE USE OF AN ENHANCED REVERSE-TRANSCRIPTASE PCR ASSAY

Objective. Because up to 40 percent of surgically treated patients wit h prostate cancer are subsequently found to be clinically understaged, a more sensitive staging modality to identify extraprostatic disease prior to surgery is required. Methods. We describe an enhanced reverse transcriptase (RT) polymerase chain reaction (PCR) assay utilizing ol igonucleotide primers specific for the human prostate-specific antigen (PSA). This assay identifies PSA-synthesizing cells from reverse tran scribed mRNA. This assay was applied to RNAs extracted from the periph eral blood lymphocytes of 65 patients with clinically localized prosta te cancer. In addition, blood from 20 women, 20 young men, 25 age-matc hed control men under treatment for benign prostatic hyperplasia (BPH) , and 18 men with established, untreated metastatic prostate cancer wa s tested. Results. An RT-PCR assay for PSA can recognize one PSA-expre ssing cell diluted into one hundred thousand lymphocytes. The sensitiv ity of this assay can be enhanced by the addition of digoxigenin-modif ied nucleotides to the PCR reaction and this assay was applied to RNAs extracted from the peripheral lymphocyte fraction of 148 prostate can cer patients and controls at this institution. Although no specimen fr om women or men without cancer was positive in this assay, 14 of 18 me tastatic prostate cancer patients were positive (77.8%). Additionally, 25 of 65 (38.5%) patients with clinically localized disease (T1-2b) w ere positive from blood specimens obtained prior to surgery. Final pat hologic results from this group of patients identified a correlation b etween positivity on this assay and the presence of capsular tumor pen etration (sensitivity, 68%; specificity, 84%) as well as a strong corr elation with the finding of carcinoma at the surgical margin (sensitiv ity, 87%; specificity, 76%). Logarithmic regression analysis of the re sults of the RT-PCR assay indicates its remarkable superiority to digi tal rectal examination, computed tomography scan, endorectal coil magn etic resonance imaging, PSA, prostate-specific antigen density, or Gle ason score for predicting the true pathologic stage of prostate cancer in these surgically treated patients. Conclusions. An RT-PCR assay us ing PSA primers to detect prostate cells in the peripheral circulation of surgical-candidate patients is significantly correlated with capsu lar penetration and tumor-positive surgical margins, This molecular as say provides a sensitive and specific means to stage correctly apparen t localized prostate cancer prior to radical prostatectomy.