Faculty Bibliography

Current imaging modalities used to stage prostate cancer clinically fail to detect extracapsular disease in a significant subset of patients. A molecular based peripheral blood assay using the reverse transcriptase polymerase chain reaction has recently been shown to be a highly sensitive staging modality for detecting extraprostatic disease preoperatively. The assay uses primers that are specific for prostate specific antigen (PSA). We compare the application of the reverse transcriptase polymerase chain reaction assay using primers specific for the human prostate specific membrane antigen with results obtained from the same specimens by reverse transcriptase polymerase chain reaction for PSA. Prostate specific membrane antigen, a recently cloned prostatic antigen, is a transmembrane glycoprotein that has been described as prostate specific. These assays were applied to ribonucleic acids extracted from the peripheral blood lymphocyte fraction of 80 patients with clinically localized prostate cancer. In addition, blood specimens from 20 female patients, 20 young male patients, 25 age-matched control men under treatment for benign prostatic hypertrophy and 20 men with established, untreated metastatic prostate cancer were tested. All 3 groups of noncancer patients had negative polymerase chain reactions for PSA as well as prostate specific membrane antigen. Of 20 metastatic prostate cancer patients 16 (80%) had positive polymerase chain reactions for PSA, while only 10 (50%) had positive results for prostate specific membrane antigen. Among the 80 patients with clinically localized disease (stages T1 to T2cN0M0), 27 and 19 had positive polymerase chain reaction for PSA and prostate specific membrane antigen, respectively, from blood specimens obtained preoperatively. Analyzing the final pathology in each patient with the reverse transcriptase polymerase chain reaction assay identified a significantly stronger correlation with tumor invasion using the results of the PSA test rather than the results of the prostate specific membrane antigen reverse transcriptase polymerase chain reaction test (67% versus 34% sensitivity for detecting capsular penetration, 87% versus 46% sensitivity for detecting disease to the surgical margin and 83% versus 16% sensitivity for detecting seminal vesicle invasion). In contrast to the reverse transcriptase polymerase chain reaction assay for PSA, a similar assay done for prostate specific membrane antigen did not correlate with pathological stage of prostate cancer.

BACKGROUND:As up to 50% of all patients with prostate cancer who have undergone radical prostatectomy are found to be understaged subsequent to surgery, a more sensitive early staging modality currently is needed. A molecular assay that detects prostate specific antigen (PSA)-synthesizing cells in the peripheral circulation of patients with prostate cancer is described. METHODS:An enhanced reverse-transcriptase polymerase chain reaction (RT-PCR) assay specific for PSA mRNA was performed on RNA extracted from blood drawn from 94 patients before radical prostatectomy. Surgical specimens were examined to determine the extent of tumor spread. The assay was compared with imaging modalities, digital rectal examination, and serum PSA level as predictors of pathology. Additionally, patients were monitored postoperatively by serum PSA level to determine any potential correlation between patient RT-PCR scores and subsequent tumor recurrence. RESULTS:Postoperative pathology revealed that 36 of the 94 patients had extraprostatic disease at the time of surgery. Enhanced RT-PCR identified 26 of these patients from preoperative blood specimens (72% sensitivity). The test was negative for 51 of the 58 patients with organ-confined disease (88% specificity). An odds ratio analysis showed that no other preoperative staging modality was related more strongly to extraprostatic or organ-confined disease. Follow-up PSA determinations revealed that RT-PCR positive patients were at higher risk for a recurrence. At 6 months after surgery, the rates for an increased PSA were 19 and 2% for RT-PCR-positive and -negative patients, respectively. CONCLUSIONS:The data from this follow-up study continue to support the utility of enhanced RT-PCR as an early staging modality for radical prostatectomy candidates.

OBJECTIVE:Because up to 40 percent of surgically treated patients with 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 oligonucleotide primers specific for the human prostate-specific antigen (PSA). This assay identifies PSA-synthesizing cells from reverse transcribed mRNA. This assay was applied to RNAs extracted from the peripheral blood lymphocytes of 65 patients with clinically localized prostate cancer. In addition, blood from 20 women, 20 young men, 25 age-matched control men under treatment for benign prostatic hyperplasia (BPH), and 18 men with established, untreated metastatic prostate cancer was tested. RESULTS:An RT-PCR assay for PSA can recognize one PSA-expressing cell diluted into one hundred thousand lymphocytes. The sensitivity of this assay can be enhanced by the addition of digoxigenin-modified nucleotides to the PCR reaction and this assay was applied to RNAs extracted from the peripheral lymphocyte fraction of 148 prostate cancer patients and controls at this institution. Although no specimen from women or men without cancer was positive in this assay, 14 of 18 metastatic prostate cancer patients were positive (77.8%). Additionally, 25 of 65 (38.5%) patients with clinically localized disease (T1-2b) were positive from blood specimens obtained prior to surgery. Final pathologic results from this group of patients identified a correlation between positivity on this assay and the presence of capsular tumor penetration (sensitivity, 68%; specificity, 84%) as well as strong correlation with the finding of carcinoma at the surgical margin (sensitivity, 87%; specificity, 76%). Logarithmic regression analysis of the results of the RT-PCR assay indicates its remarkable superiority to digital rectal examination, computed tomography scan, endorectal coil magnetic resonance imaging, PSA, prostate-specific antigen density, or Gleason score for predicting the true pathologic stage of prostate cancer in these surgically treated patients. CONCLUSIONS:An RT-PCR assay using PSA primers to detect prostate cells in the peripheral circulation of surgical-candidate patients is significantly correlated with capsular penetration and tumor-positive surgical margins. This molecular assay provides a sensitive and specific means to stage correctly apparent localized prostate cancer prior to radical prostatectomy.