Blinded evaluation of reverse transcriptase-polymerase chain reaction prostate-specific antigen peripheral blood assay for molecular staging of prostate cancer

Frequent Detection and Immunophenotyping of Prostate-Derived Cell Clusters in the Peripheral Blood of Prostate Cancer Patients

Background

Recent scientific studies have failed to determine parameters for the assessment of prostate cancer aggressiveness. The present study deals with the detection of blood-borne cancer cells based on polymerase chain reaction (PCR) and cell enrichment methods. The contradictory results reported in the literature have called into question the clinical usefulness of this diagnostic method in the preoperative staging of clinically localized prostate cancer.

Methods

We established a combined method of density gradient centrifugation and immunomagnetic separation using epithelium-specific antibodies, i.e. cytokeratins, to isolate prostate-derived circulating cells from the peripheral blood of patients with prostate cancer. Isolated cells were characterized by DNA staining and immunocytochemistry using antibodies for the detection of prostate-specific antigen (PSA), proliferation-associated proteins (MIB-1, H1 and H3) and apoptosis-associated proteins (M30, c-FasR).

Results

We applied these methods to 68 prostate cancer patients and were able to isolate cell clusters in 98%. Immunophenotypic and morphological characterization of PSA-positive prostate-derived cell clusters found in the peripheral blood of prostate cancer patients showed two main populations: 1) in 35% of the investigated prostate cancer patients we detected rounded cell aggregates of probable cancer cells expressing proliferation-associated proteins and lacking apoptosis-associated protein expression; 2) in all cases there was a high frequency of circulating dysmorphic cell clusters positive for apoptosis-associated protein expression.

Conclusion

Our results demonstrate the existence of at least two different types of blood-borne prostate-derived circulating cell clusters. Of these, only the less frequent, round, small cell clusters harbor features that are probably necessary for the cells to survive for metastatic spread.

Circulating prostate tumor cells detected by reverse transcription-PCR in men with localized or castration-refractory prostate cancer: concordance with CellSearch assay and association with bone metastases and with survival

BACKGROUND

Reverse transcription-PCR (RT-PCR) assays have been used for analysis of circulating tumor cells (CTCs), but their clinical value has yet to be established. We assessed men with localized prostate cancer or castration-refractory prostate cancer (CRPC) for CTCs via real-time RT-PCR assays for KLK3 [kallikrein-related peptidase 3; i.e., prostate-specific antigen (PSA)] and KLK2 mRNAs. We also assessed the association of CTCs with disease characteristics and survival.

METHODS

KLK3, KLK2, and PSCA (prostate stem cell antigen) mRNAs were measured by standardized, quantitative real-time RT-PCR assays in blood samples from 180 localized-disease patients, 76 metastatic CRPC patients, and 19 healthy volunteers. CRPC samples were also tested for CTCs by an immunomagnetic separation system (CellSearch; Veridex) approved for clinical use.

RESULTS

All healthy volunteers were negative for KLK mRNAs. Results of tests for KLK3 or KLK2 mRNAs were positive (> or =80 mRNAs/mL blood) in 37 patients (49%) with CRPC but in only 15 patients (8%) with localized cancer. RT-PCR and CellSearch CTC results were strongly concordant (80%-85%) and correlated (Kendall tau, 0.60-0.68). Among CRPC patients, KLK mRNAs and CellSearch CTCs were closely associated with clinical evidence of bone metastases and with survival but were only modestly correlated with serum PSA concentrations. PSCA mRNA was detected in only 7 CRPC patients (10%) and was associated with a positive KLK mRNA status.

CONCLUSIONS

Real-time RT-PCR assays of KLK mRNAs are highly concordant with CellSearch CTC results in patients with CRPC. KLK2/3-expressing CTCs are common in men with CRPC and bone metastases but are rare in patients with metastases diagnosed only in soft tissues and patients with localized cancer.

Detection of circulating tumor cells in prostate cancer patients: methodological pitfalls and clinical relevance

Disseminated malignancy is the major cause of prostate cancer-related mortality. Circulating tumor cells (CTCs) are essential for the establishment of metastasis. Various contemporary and molecular methods using prostate-specific biomarkers have been applied to detect extraprostatic disease that is undetectable by conventional imaging techniques, assessing the risk for disease recurrence after therapy of curative intent. However, the clinical relevance of CTC detection is still controversial. We review current literature regarding molecular methods used for the detection of CTCs in the peripheral blood and bone marrow biopsies of patients with prostate cancer, and we discuss the methodological pitfalls that influence the clinical significance of molecular staging.

Genomic alterations indicate tumor origin and varied metastatic potential of disseminated cells from prostate cancer patients

Disseminated epithelial cells can be isolated from the bone marrow of a far greater fraction of prostate-cancer patients than the fraction of patients who progress to metastatic disease. To provide a better understanding of these cells, we have characterized their genomic alterations. We first present an array comparative genomic hybridization method capable of detecting genomic changes in the small number of disseminated cells (10-20) that can typically be obtained from bone marrow aspirates of prostate-cancer patients. We show multiple regions of copy-number change, including alterations common in prostate cancer, such as 8p loss, 8q gain, and gain encompassing the androgen-receptor gene on Xq, in the disseminated cell pools from 11 metastatic patients. We found fewer and less striking genomic alterations in the 48 pools of disseminated cells from patients with organ-confined disease. However, we identify changes shared by these samples with their corresponding primary tumors and prostate-cancer alterations reported in the literature, evidence that these cells, like those in advanced disease, are disseminated tumor cells (DTC). We also show that DTCs from patients with advanced and localized disease share several abnormalities, including losses containing cell-adhesion genes and alterations reported to associate with progressive disease. These shared alterations might confer the capability to disseminate or establish secondary disease. Overall, the spectrum of genomic deviations is evidence for metastatic capacity in advanced-disease DTCs and for variation in that capacity in DTCs from localized disease. Our analysis lays the foundation for elucidation of the relationship between DTC genomic alterations and progressive prostate cancer.

The Use of Real-Time Reverse Transcription-PCR for Prostate-Specific Antigen mRNA to Discriminate between Blood Samples from Healthy Volunteers and from Patients with Metastatic Prostate Cancer

PURPOSE

A clinical role for nonquantitative reverse transcription-PCR (RT-PCR) using prostate-specific antigen in blood samples from patients with prostate cancer remains undefined. Assay variation and detection of prostate-specific antigen mRNA illegitimate transcription may explain inconsistent results between studies. Defining levels of prostate-specific antigen mRNA expression in blood samples from healthy volunteers and patients with prostate cancer would allow cutoffs to be established to distinguish the two groups.

EXPERIMENTAL DESIGN

Quantitative real-time RT-PCR for prostate-specific antigen mRNA was established and levels of prostate-specific antigen mRNA measured in bloods samples from healthy volunteers (n=21) and patients with localized (n=27) and metastatic (n=40) prostate cancer.

RESULTS

Levels of prostate-specific antigen mRNA were significantly higher in blood samples from patients with metastatic prostate cancer than in blood samples from patients with localized prostate cancer (P <0.001) or in blood samples from healthy volunteers (P <0.01); levels between patients with localized prostate cancer and healthy volunteers were no different. Assay sensitivity to detect patients with metastatic prostate cancer was 68% with specificity of 95%. In patients with newly diagnosed metastatic prostate cancer, monitoring response to hormonal therapy was possible with this assay. No correlation between levels of prostate-specific antigen mRNA and serum prostate-specific antigen protein levels was found, suggesting that prostate-specific antigen mRNA and serum prostate-specific antigen protein levels reflect different features of prostate cancer, i.e., circulating tumor cells and total tumor bulk, respectively.

CONCLUSIONS

Quantitative RT-PCR discriminates patients with metastatic prostate cancer from healthy volunteers and patients with localized prostate cancer but cannot discriminate patients with localized prostate cancer from healthy volunteers. A role for quantitative RT-PCR has been identified in the assessment and monitoring of patients with metastatic prostate cancer.

Quantitative real-time rt-PCR for detection of circulating prostate-specific antigen mRNA using sequence-specific oligonucleotide hybridization probes in prostate cancer patients

OBJECTIVE

A great number of studies have failed thus far to demonstrate that the presence of PSA-expressing tumor cells in the blood of prostate cancer (PC) patients is a highly sensitive prognostic marker, particularly after radical prostatectomy (RPX). These studies have only relied on qualitative or semiquantitative detection techniques, however. We report our initial experience in testing real-time RT-PCR for the detection of PSA mRNA using a quantitative online PCR system, the LightCycler(TM), and sequence-specific oligonucleotide hybridization probes.

METHODS

Blood samples were obtained before and after surgery from 129 patients undergoing RPX for localized PC and from 19 patients undergoing transurethral resection of the prostate for benign prostatic hyperplasia (BPH). Quantitative RT-PCR for the detection PSA mRNA was performed using the LightCycler system with RNA Amplification Kit Hybridization Probes and sequence-specific oligonucleotide hybridization probes.

RESULTS

PSA mRNA was detected by the LightCycler in 28 patients (39%) with pT2 tumors, in 22 patients (38%) with >pT2 tumors, but in only 3 patients (16%) with BPH. The mean values of the LNCaP cell equivalents were higher in >pT2 patients than in pT2 patients (37 x 10(3) and 104 x 10(3)) or BPH patients (7.1 x 10(3) and 4.8 x 10(3)) both preoperatively (333 x 10(3)/ml blood) and postoperatively (545 x 10(3)).

CONCLUSION

Real-time RT-PCR with the LightCycler appears to be a promising method for the preoperative detection of circulating LNCaP tumor cells in PC as reflected by PSA mRNA. Considering the low detection rates in BPH patients, the method may also be suitable for patient monitoring after RPX and could thus play an important role in deciding on early radiotherapy or even hormone ablation therapy. Additional long-term follow-up will have to show whether patients with high expression of PSA mRNA actually have an increased risk or recurrence and whether the method is suitable as well to detect progression.

Quantitative PSA RT-PCR for preoperative staging of prostate cancer

BACKGROUND

The clinical value of detecting prostate specific antigen (PSA) mRNA in the peripheral blood mononuclear cell fraction of patients (pts) by standard RT-PCR assays with localized prostate cancer remains controversial. We used a quantitative RT-PCR assay to measure the PSA mRNA copy number in addition to the qualitative PSA RT-PCR and correlated the results with clinical parameters.

METHODS

Total RNA was extracted from the peripheral blood mononuclear cell fraction of 115 prostate cancer pts prior to radical retropubic prostatectomy (RP) who received 3 months of neoadjuvant androgen deprivation. For quantitative RT-PCR, a PSA-like internal standard (IS) was added to each sample prior to reverse transcription and the PCR products for PSA and IS were selectively detected with fluorescent europium chelates after hybridization. Corresponding qualitative PSA-RT-PCR was performed for all samples.

RESULTS

The median PSA copy number was 126 (range: 0-37988). There were no significant correlations established between qualitative or quantitative RT-PCR results and given clinical parameters. Corresponding quantitative and qualitative RT-PCR results were significantly associated (P = 0.01).

CONCLUSIONS

We were unable to show any additional value of quantitative as well as qualitative PSA RT-PCR for preoperative staging of prostate cancer so far. Nevertheless, the long-term follow up of the patients has to be awaited.

Determination of prostate specific antigen mRNA in peripheral blood by reverse transcriptase polymerase chain reaction and a simple chemiluminometric hybridization assay in a high-throughput format

In recent years, the mRNA for prostate-specific antigen (PSA) has been investigated as a potential marker for molecular staging of prostate cancer. We report a simple, rapid, and sensitive assay protocol for the quantification of PSA mRNA in peripheral blood by using reverse transcriptase polymerase chain reaction (RT-PCR) and a chemiluminometric hybridization assay. A recombinant RNA internal standard (IS) that has the same size and primer binding sites as the PSA mRNA is included in the RT-PCR mixture. Total RNA from the sample is coextracted with a constant amount of IS RNA and subjected to RT-PCR. Amplified sequences are labeled with biotin during PCR by using a biotinylated upstream primer. The products are heat-denatured and hybridized with oligonucleotide-specific probes (for PSA and IS) that are immobilized in microtiter wells. Immobilization of oligonucleotide probes is achieved by adsorption of their conjugates with bovine serum albumin. The hybrids are measured using alkaline phosphatase-labeled streptavidin and a dioxetane chemiluminogenic substrate. The ratio of the luminescence values obtained for the PSA mRNA and the RNA IS is a linear function of the initial amount of PSA mRNA present in the sample prior to RT-PCR amplification. The linear range extended from 50 to 500,000 PSA mRNA copies, and the overall reproducibility of the assay, including RT-PCR and hybridization, ranged from 11.5 to 14.2%. Samples containing total RNA from PSA-expressing LNCaP cells give luminescence ratios that are linearly related to the number of cells in the range of 0.04-400 cells. The method was applied to PSA mRNA determination in peripheral blood of healthy individuals, patients with benign prostate hyperplasia, patients with prostate cancer, and patients with other types of localized cancer.

Can the reverse transcriptase-polymerase chain reaction for prostate specific antigen and prostate specific membrane antigen improve staging and predict biochemical recurrence?

OBJECTIVE

To evaluate the perioperative gene-specific primed nested reverse transcription-polymerase chain reaction (RT-PCR) for prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) for staging patients undergoing radical prostatectomy and predicting biochemical recurrence.

PATIENTS AND METHODS

In 80 consecutive patients undergoing radical prostatectomy for prostate cancer, blood samples were drawn before, during and 1 and 7 days after removing the prostate. After buffy coat and mRNA extraction, gene-specific primed nested RT-PCR was performed for PSA, PSMA and glyceraldehyde-3-phosphate dehydrogenase mRNA, and Southern blot analysis of the PCR reaction.

RESULTS

The sensitivity of gene-specific RT-PCR to detect tumour cells was comparable with random primed RT-PCR. In the 80 patients the stage distribution was pT1 in two (2.5%), pT2 in 30 (37.5%) and > or = pT3 in 48 (60%); the nodal status was pN0 in 57 (71%), pN1 in 11 (14%) and pN2 in 12 (15%). The gene-specific RT-PCR reaction for PSA and PSMA was positive in no patients with pT1, 11 (37%) with pT2 and 23 (48%) with stage > or = pT3 disease. The result for PSA was positive in 12 (52%) and for PSMA in 11 (48%) of those with positive nodal status. Neither gene-specific RT-PCR for PSA or PSMA was able to predict organ-confined disease (P > 0.5). After a median (range) follow-up of 37 (11-67) months a biochemical recurrence was predicted in 65% of patients by preoperative RT-PCR for both PSA and PSMA, with a sensitivity, specificity, positive and negative predictive value of 58%, 80%, 87% and 47%, respectively; the assay after surgery predicted a recurrence in 73%, with respective values of 68%, 84%, 84% and 57%.

CONCLUSIONS

Gene-specific primed nested RT-PCR for PSA and PSMA is a sensitive and simple assay; it might add substantial information for tumour staging in individual patients. RT-PCR before surgery allows the prediction of recurrence in 65% of cases and after surgery in 73%.

Preoperative combined nested reverse transcriptase polymerase chain reaction for prostate-specific antigen and prostate-specific membrane antigen does not correlate with pathologic stage or biochemical failure in patients with localized prostate cancer undergoing radical prostatectomy

PURPOSE

We report a prospective study examining the ability of preoperative nested reverse transcriptase polymerase chain reaction (RT-PCR) for prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSM) to predict pathologic stage and biochemical recurrence in patients with clinically localized prostate cancer treated with radical prostatectomy.

PATIENTS AND METHODS

One hundred forty-one patients were entered onto the study. Preoperative evaluation included clinical T stage, serum PSA, biopsy Gleason score, and serum RT-PCR for PSA/PSM. Univariate and multivariate logistic regression models, Kaplan-Meier estimates, and Cox proportional hazards modeling were used to identify predictors of pathologic stage and biochemical failure.

RESULTS

Seventy-three patients (51.8%) were RT-PCR positive for PSA, PSM, or both. In the multivariate logistic regression model, only initial PSA was an independent predictor of pathologic stage as defined by organ-confined disease (odds ratio [OR], 1.06; 95% confidence interval [CI], 1.00 to 1.13; P =.026) or organ-/specimen-confined disease (OR, 1.09; 95% CI, 1.02 to 1.16; P =.009). Overall Kaplan-Meier biochemical relapse-free survival (bRFS) was 85% at 59 months. Multivariate analysis of predictors for bRFS with the Cox proportional hazards model indicated that only initial PSA (OR, 1.05; 95% CI, 1.02 to 1.09; P =.004) and biopsy Gleason score (OR, 3.57; 95% CI, 1.37 to 9.58; P =.009) were independent predictors of biochemical failure. RT-PCR status did not predict pathologic stage or biochemical failure. Repeat analysis excluding 27 patients who received preoperative androgen-deprivation therapy did not change the results.

CONCLUSION

Combined nested RT-PCR for PSA and PSM is not an independent predictor of pathologic stage or biochemical failure in patients with localized prostate cancer undergoing radical prostatectomy. This assay has no clinical utility in this patient population.

Presence of circulating prostate cancer cells in African American males adversely affects survival

African-Americans (AAM) with prostate cancer are more likely to relapse than Caucasian-Americans (CAM) despite controlling for known prognostic factors. One explanation may be that micrometastatic disease in AAM behaves more aggressively than in CAM. We tested this hypothesis by comparing the reverse transcriptase polymerase chain reaction amplification of the Prostatic Specific Antigen-mRNA (RTPCR PSA-mRNA) results from peripheral blood samples of AAM and CAM with respect to disease outcome. We evaluated the peripheral blood of 246 consecutive patients at the time of radical prostatectomy. The RTPCR PSA-mRNA test for determination of circulating prostate cancer cells was performed. The results were stratified by races and correlated with standard clinico-pathological variables and disease free survival. 27% and 23% of AAM and CAM patients were RTPCR PSA-mRNA positive, respectively. The RTPCR PSA-mRNA status correlated with the pathologic stage in CAM but not in AAM, (p = 0.05). There was no association with Gleason score, PSA level, or clinical stage with the RTPCR PSA-mRNA status in either group. AAM with organ-confined prostate cancer were marginally more likely to have circulating prostate cells than similarly staged CAM (24% vs. 17%). In AAM but not CAM who had prostate cancer, the RTPCR PSA-mRNA status correlated with and was an independent predictor of disease-free survival. Our data suggests that, though the likelihood of having circulating prostate cells is the same in AAM and CAM, the presence of circulating prostate cells in AAM is predictive of a worse outcome. This may partially explain the worse prognosis in AAM vs. CAM with clinically localized prostate cancer.

Detection of prostate-specific antigen RNA before and after radical retropubic prostatectomy and transurethral resection of the prostate using "Light-Cycler"-based quantitative real-time polymerase chain reaction

OBJECTIVES

To report our initial experience gained in establishing real-time reverse transcriptase-polymerase chain reaction (RT-PCR) detection of prostate-specific antigen (PSA) mRNA using the quantitative online PCR system LightCycler. Many studies have thus far failed to provide the desired proof that the detection of circulating PSA-expressing tumor cells with RT-PCR in the blood samples of patients with prostate cancer (PCa) is a highly sensitive prognostic and course marker. One of the possible reasons is the lack of reliable quantification methods.

METHODS

Blood samples before and after surgery were obtained from 87 patients who underwent radical prostatectomy for locally confined PCa and 27 patients who underwent transurethral resection of the prostate for benign prostatic hyperplasia. Eight days postoperatively, additional blood samples were obtained from the patients with PCa. Quantitative no-nested RT-PCR for PSA mRNA (291 bp) was performed using the LightCycler system applying the SYBR Green protocol. The number of circulating LNCaP tumor cell-equivalents per sample was estimated from the mean amplification value measured in a given number of LNCaP cells.

RESULTS

PSA mRNA was detected preoperatively in 19 patients with Stage pT2 tumor (40%) and in 28 patients with tumor greater than Stage pT2 (72%), but in only 2 patients with benign prostatic hyperplasia (8%; analysis of variance, P <0.001). Significant quantitative differences were observed among Stage pT2 disease (1034 LNCaP tumor cell-equivalents/mL), greater than Stage pT2 disease (7830 cells/mL), and benign prostatic hyperplasia (58 cells/mL; analysis of variance for all groups, P <0.001). The correlation between the detection of PSA expression by RT-PCR and the Gleason score and serum PSA value was statistically significant.

CONCLUSIONS

Our results show that the initial experience with the LightCycler system for PSA-assisted detection of circulating PSA mRNA in PCa by RT-PCR may be a promising preoperative prognostic marker for organ-confined or locally advanced PCa. Long-term follow-up of these patients with PCa must demonstrate the clinical value of molecular diagnostics with quantitative RT-PCR systems.

Molecular prediction of progression in patients with conservatively managed prostate cancer

OBJECTIVES

To report our results with the use of reverse transcriptase-polymerase chain reaction (RT-PCR) as a potential predictor of prostate cancer (CaP) progression in patients managed with watchful waiting. There has been much recent debate about the safety of treating older patients with localized CaP with watchful waiting. The RT-PCR is an assay that can detect small numbers of prostate cells in circulating blood.

METHODS

Blood samples were taken from male and female control patients and from patients with advanced, hormone-treated and untreated localized (watchful-waiting) CaP. Sensitive nested RT-PCR assays were carried out on these samples using primers for both prostate-specific antigen (PSA) and prostate-specific membrane antigen mRNA.

RESULTS

Fifty-one blood samples were taken from patients managed with watchful waiting. Fourteen of these had positive RT-PCR results. These patients had a significantly higher PSA velocity than did the patients with negative RT-PCR results. Circulating prostate cells were detected in 18 of 24 patients with advanced CaP, 2 of 34 patients with stable, hormone-treated CaP, and in none of the negative controls. The assay was able to detect 20 LNCaP cells reliably when added to a 5-mL volunteer blood sample.

CONCLUSIONS

A significant minority (27%) of patients with untreated localized CaP had detectable circulating prostate cells, and these patients tended to have a progressively rising serum PSA level. Despite low-grade disease and sometimes low serum PSA values, these patients may be at risk of early metastatic progression. RT-PCR, in conjunction with existing prognostic tests, may be of use in predicting which "watchful-waiting" patients are at risk of early progression.

The role of imaging studies and molecular markers for selecting candidates for radical prostatectomy

For the typical patient who has newly diagnosed prostate cancer, clinically organ-confined disease of moderate grade, and a PSA less than 10 ng/mL, the current role of imaging studies and molecular biomarkers is limited. Bone scans are not necessary for newly diagnosed men with a PSA less than 10 ng/mL in the absence of bone pain. Similarly, abdominal and pelvic CT scanning rarely provides any useful diagnostic or staging information when the PSA is less the 20 ng/mL and is indicated rarely. Endorectal coil MR imaging adds staging information for patients with a PSA between 10 and 20 ng/mL, a Gleason score of 7 or less, and 50% or more positive biopsies on a sextant sampling. Indium 111 capromab pendetide scanning (ProstaScint) is FDA-approved to evaluate newly diagnosed patients at high risk for metastases. These patients have a Gleason score of 7 or greater and a PSA greater than 20 ng/mL, a Gleason score of 8 to 10 regardless of the PSA value, or clinical stage T3 disease and a Gleason score of 6 or greater. RT-PCR testing of blood or bone marrow for prostate-specific or prostate cancer-specific gene expression, or "molecular staging," is a promising technique whose current use is still investigational. Much useful information may be gained by careful study of prostate needle biopsy material. Aside from current Gleason grading and the number or percentage of cores involved with cancer, no molecular biomarker is approved for clinical use. p27, p53, bcl-2, Ki-67 (MIB-1), and the assessment of neovascularity hold promise, but prospective multicenter studies are needed. In the long-term, multiple gene expression profiling of biopsy material using gene chips may revolutionize the care of patients with prostate cancer and those who elect radical prostatectomy.

Molecular detection and characterization of circulating tumor cells and micrometastases in prostatic, urothelial, and renal cell carcinomas

The detection and molecular characterization of circulating tumor cells (CTCs) and micrometastases in urinary tract and prostatic tumors may have important prognostic and therapeutic implications. In the last decade, numerous groups have attempted the detection of occult tumor cells in renal, prostatic, and urothelial carcinomas using the highly sensitive reverse-transcriptase polymerase chain reaction (RT-PCR). In prostatic carcinoma (PC), tissue-specific transcripts were detected with high specificity in the blood of patients with localized and advanced disease. PCR assays for PC detection were shown to be strong predictors of poorer outcome in some reports, while a lack of prognostic significance was found in other studies. There was a vast difference in the PCR positivity rates between various groups studying PC. This discrepancy could be due to variations in PCR methodology. In urothelial and renal cell carcinoma, the amount of research on the subject is still too limited. Currently, these assays for occult tumor cells are promising but are not yet ready to use in PC and urinary tract tumors. Because of the many limitations of PCR (e.g., false positives), many groups are developing new approaches for the detection of occult tumor cells. The most attractive technique involves immunomagnetic isolation of intact CTC and micrometastases prior to downstream analysis. The tumor-rich magnetic fraction can be subjected to RT-PCR, immunocytochemistry, and in situ hybridization. This will lead to better quantification and molecular characterization of these tumor cells.

Impact of different variables on the outcome of patients with clinically confined prostate carcinoma: prediction of pathologic stage and biochemical failure using an artificial neural network

BACKGROUND

The advent of advanced computing techniques has provided the opportunity to analyze clinical data using artificial intelligence techniques. This study was designed to determine whether a neural network could be developed using preoperative prognostic indicators to predict the pathologic stage and time of biochemical failure for patients who undergo radical prostatectomy.

METHODS

The preoperative information included TNM stage, prostate size, prostate specific antigen (PSA) level, biopsy results (Gleason score and percentage of positive biopsy), as well as patient age. All 309 patients underwent radical prostatectomy at the University of Colorado Health Sciences Center. The data from all patients were used to train a multilayer perceptron artificial neural network. The failure rate was defined as a rise in the PSA level > 0.2 ng/mL. The biochemical failure rate in the data base used was 14.2%. Univariate and multivariate analyses were performed to validate the results.

RESULTS

The neural network statistics for the validation set showed a sensitivity and specificity of 79% and 81%, respectively, for the prediction of pathologic stage with an overall accuracy of 80% compared with an overall accuracy of 67% using the multivariate regression analysis. The sensitivity and specificity for the prediction of failure were 67% and 85%, respectively, demonstrating a high confidence in predicting failure. The overall accuracy rates for the artificial neural network and the multivariate analysis were similar.

CONCLUSIONS

Neural networks can offer a convenient vehicle for clinicians to assess the preoperative risk of disease progression for patients who are about to undergo radical prostatectomy. Continued investigation of this approach with larger data sets seems warranted.

Value of reverse transcription polymerase chain reaction assay in pathological stage T3N0 prostate cancer

BACKGROUND

We tested the ability of the nested reverse transcription polymerase chain reaction (RT-PCR) assay to detect signs of biochemical recurrence of prostate cancer in the lymph nodes and peripheral blood of patients with pT3N0 prostate cancer.

METHODS

Using lymph nodes and pre- and postoperative peripheral blood dissected from 30 patients with pT3N0 prostate cancer treated by radical prostatectomy, we used RT-PCR for prostate-specific membrane antigen (PSM) and serum prostate-specific antigen (PSA) to determine the presence of prostate cancer. Results of the nested RT-PCR assay were compared with pathological stages and biochemical recurrence.

RESULTS

Two of 13 patients with capsular penetration (15%), 6 of 10 patients with invasion of seminal vesicles (60%), and 3 of 7 patients with a positive surgical margin (43%) were RT-PCR-positive for PSM and/or PSA in the lymph nodes. Results of preoperative RT-PCRs of peripheral blood for PSM and for PSA significantly differed between positive and negative results of RT-PCR in lymph nodes (P < 0.001 and P < 0.001, respectively). Results of postoperative RT-PCRs of peripheral blood for PSM and for PSA also significantly different between positive and negative results of RT-PCR in lymph nodes (P = 0.011 and P = 0.001, respectively). Nine of 11 patients with positive nested RT-PCR for PSM and/or PSA in the lymph nodes (82%) experienced biochemical recurrence. Significant difference in Kaplan-Meier recurrence-free actuarial curves was noted between patients who nested positive and negative on RT-PCR in the lymph nodes, pre- and postoperative peripheral blood, biopsy and prostatectomy Gleason score, and preoperative PSA values. In multivariate analysis, biopsy and prostatectomy Gleason score (P = 0.026, P = 0.020, respectively), pre- and postoperative RT-PCR for PSM in peripheral blood (P = 0.030 and P = 0.040, respectively), and RT-PCR for PSM in lymph nodes (P = 0.035) were independent prognostic factors.

CONCLUSIONS

Nested RT-PCR assay of the lymph nodes or peripheral blood significantly predicted biochemical recurrence after surgery. It may help identify patients at risk for recurrence and progression of prostate cancer.

Molecular detection and characterisation of circulating tumour cells and micrometastases in solid tumours

The detection and molecular characterisation of circulating tumour cells (CTC) and micrometastases may have important prognostic and therapeutic implications. Because their numbers are very small, these tumour cells are not easily detected using conventional methods. In the last decade, numerous groups have attempted to detect occult tumour cells in solid malignancies using the highly sensitive reverse transcriptase polymerase chain reaction (RT-PCR). These assays were in the vast majority directed against tissue-specific markers. PCR was shown to be superior to conventional techniques in detecting occult tumour cells allowing the identification of one malignant cell mixed with 1-10 million normal cells. In some tumours like melanoma and prostatic carcinoma, tissue-specific transcripts were detected with high specificity in the blood of patients with localised and advanced disease. In some reports, PCR was shown to be a strong predictor of poorer outcome. However, due to the many limitations of PCR (e.g false-positives), many groups are developing new approaches for the detection of occult tumour cells. The most attractive technique involves immunomagnetic isolation of CTC and micrometastases prior to downstream analysis. The tumour-rich magnetic fraction can be subjected to RT-PCR, immunocytochemistry and in situ hybridisation. This will lead to better quantification and molecular characterisation of these tumour cells. In conclusion, the molecular detection and characterisation of occult tumour cells offer a great opportunity for better stratifying patients with solid tumours and for developing new prognostic markers and targeted therapies.

Review: polymerase chain reaction detection of micrometastases and circulating tumor cells: application to melanoma, prostate, and thyroid carcinomas

The main strategy used for the detection of circulating tumor cells (CTC) and micrometastases in solid tumors is the polymerase chain reaction (PCR) amplification of tissue specific messenger RNA present in the tumor cells. PCR was more sensitive than conventional techniques, allowing the identification of one tumor cell diluted into 1 mL of blood. PCR was shown to be specific in most studies related to the detection of CTC and marrow micrometastases in melanoma and prostate carcinoma (PC). PCR positivity for thyroid markers was reported in the blood of control subjects. Large variations in the PCR positivity rates and the prognostic value of these assays have been encountered in PC and melanoma. There was a correlation between PCR and stage in some but not all the studies. Despite these discrepancies, many investigators have shown PCR to be predictive of outcome in PC and especially in melanoma. PCR in blood and bone marrow was an independent predictor of overall and disease-free survival in melanoma patients rendered surgically free of disease. These tests may help better stratify patients for radical surgeries and adjuvant therapy. Large prospective and interlaboratory studies are needed to confirm the accuracy and prognostic value of these assays.