Reverse transcriptase-polymerase chain reaction assays for prostate cancer

Isolation and characterization of circulating tumor cells in prostate cancer

Circulating tumor cells (CTCs) are tumor cells found in the peripheral blood that putatively originate from established sites of malignancy and likely have metastatic potential. Analysis of CTCs has demonstrated promise as a prognostic marker as well as a source of identifying potential targets for novel therapeutics. Isolation and characterization of these cells for study, however, remain challenging owing to their rarity in comparison with other cellular components of the peripheral blood. Several techniques that exploit the unique biochemical properties of CTCs have been developed to facilitate their isolation. Positive selection of CTCs has been achieved using microfluidic surfaces coated with antibodies against epithelial cell markers or tumor-specific antigens such as EpCAM or prostate-specific membrane antigen (PSMA). Following isolation, characterization of CTCs may help guide clinical decision making. For instance, molecular and genetic characterization may shed light on the development of chemotherapy resistance and mechanisms of metastasis without the need for a tissue biopsy. This paper will review novel isolation techniques to capture CTCs from patients with advanced prostate cancer, as well as efforts to characterize the CTCs. We will also review how these analyzes can assist in clinical decision making.

CONCLUSION

The study of CTCs provides insight into the molecular biology of tumors of prostate origin that will eventually guide the development of tailored therapeutics. These advances are predicated on high yield and accurate isolation techniques that exploit the unique biochemical features of these cells.

Prostate specific membrane antigen mRNA in blood as a potential predictor of biochemical recurrence after radical prostatectomy

We investigated whether the detection of prostate specific membrane antigen (PSMA) in blood preoperatively has predictive value for biochemical recurrence (BCR) after radical prostatectomy in patients with prostate cancer. All 134 patients scheduled to receive radical prostatectomy for prostate cancer were prospectively enrolled. The authors used nested reverse transcriptase-polymerase chain reaction (RT-PCR) assay to detect PSMA mRNA-bearing cells in peripheral blood, and analyzed the ability of PSMA mRNA positivity to predict BCR after surgery. PSMA-mRNA was detected in 24 (17.9%) patients by RT-PCR. Over a median follow-up of 20 months (range, 3 to 46 months), BCR developed in 15 patients (11.2%) and median time to BCR was 7 months (range, 3 to 25 months). Kaplan-Meier analysis revealed a significant difference between those positive or negative for PSMA in terms of recurrence-free actuarial probability (log rank P=0.0039). Multivariate analysis showed that positivity for PSMA mRNA (HR: 3.697, 95% CI 1.285-10.634, P=0.015) and a biopsy Gleason score of >or=7 (HR: 4.500, 95% CI 1.419-14.274, P=0.011) were independent preoperative predictors of BCR. The presence of PSMA mRNA in peripheral blood can be used to predict BCR after radical prostatectomy.

Detection of prostate specific transcripts in the peripheral blood during brachytherapy predicts postoperative PSA kinetics

BACKGROUND

We evaluated whether detection of prostate-specific antigen (PSA) and human kallikrein 2 (hK2) transcripts in the peripheral blood during brachytherapy could predict biochemical outcome.

METHODS

Eighty-one patients who underwent (125)Iodine-based brachytherapy for localized prostate cancer (Gleason score <8, PSA <20 ng/ml, stage <T3), participated in the study. Brachytherapy was given to 35 patients as monotherapy, to 36 in combination with androgen deprivation therapy (ADT), and to 10 in combination with external beam radiation and ADT. Blood samples from 80 patients were available for analysis. Nested RT-PCR means was used to detect mRNA expression of PSA and hK2 in the peripheral blood. Their expression was analyzed before, during and 1 month after brachytherapy. Patients' biochemical outcome (blood PSA levels) during 3 years of follow-up was correlated with the PCR results.

RESULTS

The incidence of PSA and hK2 mRNA expression in the peripheral blood was significantly higher during than before or after the procedure. Patients with concurrent positive PSA and hK2 PCR results during brachytherapy had higher postoperative blood PSA values and a slower decline rate of PSA compared with patients with negative PSA and hK2 PCR results. No correlations were found between pre- and postbrachytherapy PCR results and biochemical outcome. ADT was the only significant factor that affected PSA and hK2 mRNA expression during brachytherapy.

CONCLUSIONS

Our short-term results suggest that detection of PSA and hK2 transcripts in the peripheral blood of prostate cancer patients during brachytherapy could serve as a predictor of biochemical outcome.

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.

Reverse transcriptase-polymerase chain reaction and immunohistochemical studies for detection of prostate stem cell antigen expression in prostate cancer: potential value in molecular staging of prostate cancer

OBJECTIVES

To determine whether detection of prostate stem cell antigen (PSCA) expression has potential for molecular staging in prostate cancer (PCa), we examined the relationship between established prognostic factors, biochemical recurrence (BCR) and PSCA expression.

METHODS

This study was comprised of 66 patients who underwent radical prostatectomy for the treatment of PCa. We employed reverse transcriptase-polymerase chain reaction (RT-PCR) to detect PSCA mRNA-bearing cells in peripheral blood, and used immunohistochemical (IHC) techniques to identify PSCA protein expression in microarrayed tissue.

RESULTS

PSCA-mRNA was detected in the peripheral blood of nine (13.6%) patients by RT-PCR. Whereas 3.2% of patients with low-grade disease were PSCA positive, 22.9% of patients with high-grade disease were PSCA positive (P = 0.030). There was also a significant relationship of RT-PCR PSCA positivity to whether or not the tumor was confined to the prostate. Whereas only 6.8% of patients with prostate-confined disease were RT-PCR PSCA positive, 27.3% of extraprostatic diseases were RT-PCR PSCA positive (P = 0.022). IHC studies of tumor tissue microarrays demonstrated that PSCA expression intensity was related to both extraprostatic extension (P = 0.014) and positive surgical margin (P = 0.053). Whereas 23.8% of prostate-confined diseases were high intensity, 54.5% of extraprostatic diseases were high intensity. BCR developed in seven patients (10.6%) during the follow-up period (median, 16.2 months; range, 9-25 months). Prognostic factors increasing the risk of BCR included: seminal vesicle invasion (P = 0.004), extraprostatic disease (P = 0.019), lymphovascular emboli (P = 0.036) and RT-PCR PSCA positivity (P = 0.004) in univariate analysis.

CONCLUSIONS

We were able to detect PSCA mRNA-bearing cells in peripheral blood by RT-PCR, and also identify PSCA protein expression in tumors by IHC analysis of tissue microarrays. RT-PCR PSCA positivity in peripheral blood may be a potential modality for molecular staging of PCa.

Correlation between CD8+ T cells specific for prostate-specific antigen and level of disease in patients with prostate cancer

Modest work has been performed to improve the sensitivity of residual disease detection or investigate the contribution that the immune system makes in controlling metastatic tumor growth, in particular, the frequency and biological actions of peptide-specific CD8+ T lymphocytes in limiting metastatic disease and/or maintaining remission. Fifty-three peripheral blood samples from 32 prostate cancer (PC) patients were investigated for the presence of circulating prostate-specific antigen (PSA)-expressing cells (CPECs) using a highly sensitive and specific assay combining immunomagnetic epithelial cell enrichment with nested RT-PCR of PSA mRNA. Using HLA-A2 tetramer complexes, frequency of CD8+ T cells specific for PSA-derived peptides was determined. Additionally, serum concentrations of PSA and testosterone were measured. CPECs were detected in 26% of peripheral blood samples from PC patients. CD8+ T cells specific for PSA-derived peptides were detected at low frequency in HLA-A2-positive PC patients. The correlation between these PSA-specific CD8+ T cells and residual prostate tumor cells and clinical measures was investigated. Our data suggest that frequency of PSA-specific CD8+ T cells is correlated to CPECs, but not to serum PSA level.

Prognostic Value of Combined “Triple”-Reverse Transcription-PCR Analysis for Prostate-Specific Antigen, Human Kallikrein 2, and Prostate-Specific Membrane Antigen mRNA in Peripheral Blood and Lymph Nodes of Prostate Cancer Patients

PURPOSE

We present the largest study of both peripheral blood and lymph node samples examining the utility of reverse transcription-polymerase chain reaction (RT-PCR) for established molecular markers as a diagnostic tool in the molecular staging of prostate cancer patients undergoing radical prostatectomy.

EXPERIMENTAL DESIGN

Peripheral blood from 358 patients was obtained before radical prostatectomy. Corresponding obturatory lymph node samples were collected from 153 of these patients. Nested RT-PCR for prostate-specific antigen (PSA), human kallikrein 2 (hK2), and prostate-specific membrane antigen (PSMA) were performed on cDNA from peripheral blood. The lymph node cDNA was analyzed for PSA und hK2 expression.

RESULTS

RT-PCR in peripheral blood was positive in 124 (34.6%) of 358 samples for PSA, 215 (60.1%) of 358 for PSMA, and 97 (27.1%) of 358 for hK2. Comparison of positive RT-PCR rates of pT(2) and pT(3) tumors in corresponding peripheral blood for PSA, PSMA, and hK2 were 31.9 and 40.0%, 58.8 and 62.5%, and 26.9 and 27.5%, respectively. Histopathologically, cancer-free lymph node samples were positive in RT-PCR for PSA and hK2 in 70 (49.6%) of 141 and 89 (63.2%) of 141 of cases. All histologically positive lymph node samples (n = 12, pN+) were positive for PSA RT-PCR. PSA RT-PCR alone, as well as combined PSA/PSMA RT-PCR evaluation, in peripheral blood showed a significant association with grading. PSA RT-PCR lymph node-negative samples were significantly less likely positive in their corresponding peripheral blood RT-PCR sample.

CONCLUSIONS

Although the preoperative PSA RT-PCR in peripheral blood correlated with the grading of prostate cancer, no combination of RT-PCR results using "triple" markers (PSA, hK2, PSMA) in peripheral blood and/or lymph nodes yielded additional preoperative staging information.

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.

Renal mRNA levels as prognostic tools in kidney diseases

Molecular biologic techniques are currently considered as new diagnostic and prognostic parameters with a sensitivity and specificity exceeding those of histologic and functional data currently used in clinical practice. The results in various clinical settings have been of limited value up to now. This study is an investigation of the use of tissue levels of RNA determined in routine clinical kidney biopsies as prognostic tools. The focus was on RNA encoding for molecules known to be involved in the pathogenesis of renal disorders. Fresh kidney biopsy tissue was obtained from 52 patients with various renal diseases. The GFR was followed for 12 mo. The extent of glomerulosclerosis and interstitial fibrosis in the biopsies was determined with quantitative digital image analysis. Glomerular and tubulointerstitial compartments from each biopsy specimen were separated, and mRNA levels of TGF-beta, collagen I, collagen IV, and fibronectin were quantitated by real-time PCR. Correlations, along with 95% confidence intervals (CI), between all variables tested at time biopsy were determined. To assess their prognostic value, these variables were correlated with the slope of GFR within several time intervals after biopsy. In addition, to evaluate the predictive value of the variables for outcome in individual patients, differences for each variable were tested between patients showing progressive decline in renal function (slope GFR < 0) and patients showing stable or improving renal function over time (slope GFR >or= 0). In chronic renal diseases, the extent of histologic damage correlated with the GFR at the time of biopsy (r = -0.44; CI -0.68 to -0.11), but it did not correlate with the slope expressing a change in GFR after the biopsy. Tubulointerstitial TGF-beta mRNA levels correlated with the rate of change in GFR between time of biopsy and 1 mo later (r = 0.41; CI, 0.07 to 0.67). The GFR at the time of biopsy correlated with the slope of change in GFR between time of biopsy and 12 mo later (r = -0.50; CI, -0.73 to -0.18). In chronic renal diseases, glomerular fibronectin mRNA levels, in comparison with the GFR at time of biopsy, correlated relatively strongly with the slope of change in GFR between 3 and 12 mo (r = 0.50; CI, 0.16 to 0.74). Patients with favorable renal outcome after 12 mo showed significantly higher TGF-beta mRNA levels and lower proteinuria levels at time of biopsy (P < 0.05) than patients with a progressive decline in renal function. This study shows that mRNA levels measured in kidney biopsies can function as prognostic tools in human renal diseases. In particular, relatively high levels of tubulointerstitial TGF-beta mRNA and glomerular fibronectin mRNA are associated with less deterioration in renal function.

Proliferation of prostate cancer cells in the bone marrow predicts recurrence in patients with localized prostate cancer

BACKGROUND

Reverse-transcription polymerase chain reaction (RT-PCR) amplification of prostate specific antigen (PSA) mRNA has been used to detect the presence of prostate cancer cells in the peripheral blood and bone marrow of patients with clinically localized disease. Some studies have demonstrated a correlation between detection of PSA-mRNA and disease recurrence. However, many RT-PCR-positive patients remain disease-free. We propose that phenotypic characterization of individual micrometastatic cells may provide more prognostic information than mere detection of such cells.

METHODS

We studied 58 patients undergoing radical prostatectomy for clinically localized disease whose bone marrow had been found to contain PSA-mRNA by RT-PCR. Immunohistochemical detection and phenotypic characterization of micrometastatic cells was performed using a two-color technique: cytokeratin antibody for detection and the MIB-1 antibody for proliferation. The clinical endpoint was disease recurrence.

RESULTS

One or more micrometastatic cells were proliferating in 36.2% of the patients; the disease-free survival rate was 76.2% in this group. In contrast, in the patients with non-proliferating cells, 97.3% remained disease-free (P = 0.025). Multivariate analysis demonstrated that the presence of proliferating cells was the only preoperative variable that correlated with disease-free survival (P = 0.05).

CONCLUSIONS

Determination of the phenotype of individual micrometastatic cells can contribute prognostic information above and beyond the mere determination of their presence or absence. Phenotypic characterization of individual micrometastatic cells may ultimately be used to select patients for systemic therapy given either alone or in combination with local therapy.

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.

Reverse transcriptase polymerase chain reaction (RT-PCR) detection of melanoma-related transcripts in the peripheral blood and bone marrow of patients with malignant melanoma. What have we learned?

The detection of circulating tumor cells (CTC) and bone marrow micrometastases (BMM) by reverse transcriptase polymerase chain reaction (RT-PCR) may help predict recurrence and survival in malignant melanoma (MM). Since the appearance of the original article by Smith et al. in 1991 (Lancet 338:1227), several groups have attempted the detection of CTC and BMM in MM using RT-PCR for melanocytic specific markers, mainly tyrosinase mRNA. Most studies show that tyrosinase is not present in the PB and BM of control individuals without MM. The PCR positivity rates in MM are extremely variable, ranging from 0% to 100%. There was a correlation between RT-PCR and stage in some but not all of the studies. These disparate findings could in part be explained by differences in RNA extraction and blood separation techniques, to unrecognized contamination leading to false positive results, or differences in patient selection. Despite these discrepancies, we and others have shown that RT-PCR for tyrosinase mRNA in PB is able to predict overall survival (OS) and disease-free survival (DFS) in a statistically significant manner. In AJCC stage II-IV patients rendered surgically free of disease, we found that blood tyrosinase positivity was an independent predictor of OS and DFS. We also found that BM tyrosinase positivity is an independent predictor of DFS in the same group of patients. RT-PCR may help identify subgroups of patients at high risk for early relapse for more aggressive adjuvant therapy. Large prospective studies and interlaboratory quality assurance initiatives are necessary to confirm the accuracy and prognostic value of these RT-PCR assays.

Comparison of telomerase activity and GSTP1 promoter methylation in ejaculate as potential screening tests for prostate cancer

New diagnostic tools are needed for the early detection of prostatic cancer. The molecular detection of prostate cancer cells in ejaculates was evaluated using complementary PCR-based methods. LNCaP cells, a cell line derived from prostatic carcinoma, were spiked into normal seminal ejaculates and the prostatic epithelial component of the specimens was isolated by immunomagnetic bead sorting, using a monoclonal antibody to prostate-specific membrane antigen (PSMA). Ejaculates from nine patients with a recent diagnosis of prostate cancer were processed in a similar fashion, using LNCaP-spiked aliquots as an internal positive control. Telomerase expression was evaluated by the telomeric repeat amplification protocol (TRAP) and glutathione S-transferase gene promoter (GSTP1) hypermethylation was evaluated by methylation-sensitive restriction endonuclease digestion and PCR amplification. Telomerase activity was detected in LNCaP cells recovered from normal seminal ejaculates but was not found in all nine samples from patients with prostate cancer. The sensitivity of GSTP1 analysis was similar to telomerase analysis for the detection of LNCaP cells from normal ejaculate samples but was positive in ejaculates from four out of nine patients with prostate cancer. GSTP1 DNA methylation status is more sensitive than telomerase analysis for the detection of malignant cells in seminal ejaculates from patients with 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.

Detection of prostatic specific membrane antigen messenger RNA using immunobead reverse transcriptase polymerase chain reaction

The present study was performed to detect circulating prostatic carcinoma (PC) cells using a novel three-step immunobead reverse transcriptase (RT) polymerase chain reaction (PCR) assay for prostatic specific membrane antigen (PSMA) messenger RNA (mRNA). The sensitivity and specificity of this technique was assessed and the incidence of immunobead RT-PCR positivity correlated with progressive metastatic disease and serum prostatic specific antigen (PSA) levels. Fifty peripheral blood (PB) samples from 46 patients with PC were incubated with magnetic beads coated with Ber-EP4 antibody directed against the human epithelial antigen a membrane antigen widely expressed by epithelial cells. The epithelial cell-enriched magnetic fraction was then subjected to mRNA isolation using oligo-deoxythymidine (dT) magnetic beads. Nested RT-PCR for PSMA was performed on the mRNA oligo-dT complex and the identity of the RT-PCR products was confirmed by Southern blotting. Twenty-one PB samples from 8 control subjects without PC were also evaluated. Three-step immunobead PSMA RT-PCR was able to detect one PC cell per 1 mL of PB. The positivity rate of the RT-PCR assay was significantly higher (11 of 25; 44%) in patients with metastatic tumor than in patients with non-metastatic disease (1 of 21; 5%) (P = 0.003). In patients with metastatic PC, RT-PCR positivity was much higher in patients with progressive disease (10 of 13; 77%) than in patients with responding or stable disease (1 of 12; 8%) (P = 0.001). There was a statistically significant correlation between immunobead PSMA PCR positivity and high levels of serum PSA (P = 0.005). All control subjects without PC tested negative for PSMA PCR. The three-step immunobead RT-PCR for PSMA can detect circulating PC cells with high specificity and sensitivity. Preliminary data show a strong correlation between immunobead PCR positivity, the presence of progressive metastatic disease, and high levels of serum PSA.

Circulating Prostate Cancer Cells Detected by Reverse Transcription-Polymerase Chain Reaction (RT-PCR): What Do They Mean?

BACKGROUND: Molecular techniques have been developed recently to assess for circulating tumor cells. This "molecular staging" of prostate cancer uses the reverse transcription-polymerase chain reaction (RT-PCR) to detect cells that contain PSA or PSMA in the bloodstream. Currently, the clinical application of this concept is controversial. METHODS: The authors discuss the current status of molecular biologic methods to detect circulating prostate cancer cells. They report on the limitations of the technology and the advances that will allow the quantification of these circulating cells. RESULTS: Studies generally indicate an increasing level of PSA RT-PCR positivity as disease advances. However, reports have been significantly diverse, and there is no clear explanation for this disparity. CONCLUSIONS: The determination of the "circulating prostate cancer cell load" by RT-PCR or other techniques may prove to be useful in the management of patients with prostate cancer, but questions remain to be answered before we can develop and assess new therapeutic strategies that will advance the treatment of prostate cancer before metastasis becomes evident. A better understanding of the biology of tumor cells present in the circulatory system is also needed.

Clinical implications of prostate‐specific antigen (PSA)

Prostate-specific antigen(PSA) is currently the tumour marker of choice for prostatic carcinoma. This article examines the current literature on the application of PSA for cancer detection (concentrating on values of PSA in the normal and 'grey' areas of 2.5-10 ng/ml), in staging of the disease and prediction of treatment response. These areas in particular have been refined by the use of PSA indices (PSA density, velocity, age ranges) and the article focuses on the recent studies analysing their standing in clinical practice.

Prostate-specific antigen and new related markers for prostate cancer

Although prostate-specific antigen (PSA), or human kallikrein 3, is the most valuable tool available for the diagnosis and management of prostate cancer, as currently used it is insufficiently sensitive and specific for early detection or staging of the malignancy. Many new concepts have been introduced in order to optimize the clinical use of PSA measurements, but each one has its own drawbacks. The molecular forms of PSA, especially the free PSA, seem to be useful for the detection of prostate cancer in men with PSA concentrations falling in the 4-10 microg/l range. New molecular techniques, such as reverse transcriptase polymerase chain reaction for the detection of minimal amounts of PSA messenger RNA and prostate-specific membrane antigen, offer new promise for the prognosis and possibly staging of prostate cancer. On the other hand, human kallikrein 2, a serine protease closely related to PSA that is also expressed predominantly in the prostate, may be a new adjuvant marker for prostate cancer. As for its biological functions, PSA can no longer be regarded as a specific prostate molecule associated mainly with semen liquefaction when it has a possible role as a prognostic indicator in female breast cancer. The biological role of PSA in normal tissues and tumors may be much more complex than previously thought and requires further investigation.

Stage T1c prostate cancer: defining the appropriate staging evaluation and the role for pelvic lymphadenectomy

A good staging system should be able to accurately reflect the natural history of a malignant disease, to express the extent of the disease at the time of diagnosis, and stratify patients in prognostically distinctive groups. The staging system for prostate cancer, as it is today, fails to fulfill these requirements. Approximately one third of the patients who undergo surgery for complete excision of prostate cancer in fact do not have a localize disease. The incidence of tumor at the inked margin may reach 30% for T1 stage and up to 60% for clinical T2b prostate cancer according to comparison with pathologic examination of resected specimen. Several concepts have been recently proposed as a means of improving the accuracy of the available staging system. In this paper, we review current aspects of clinical and pathological staging of prostate cancer, and the importance of these new concepts on the early stages of prostate cancer.