Stability of free and total prostate specific antigen in serum from patients with prostate carcinoma and benign hyperplasia

Biomarkers for prostate cancer: prostate-specific antigen and beyond

In recent years, several new biomarkers supplementing the role of prostate-specific antigen (PSA) have become available for men with prostate cancer. Although widely used in an ad hoc manner, the role of PSA in screening asymptomatic men for prostate cancer is controversial. Several expert panels, however, have recently recommended limited PSA screening following informed consent in average-risk men, aged 55-69 years. As a screening test for prostate cancer however, PSA has limited specificity and leads to overdiagnosis which in turn results in overtreatment. To increase specificity and reduce the number of unnecessary biopsies, biomarkers such as percent free PSA, prostate health index (PHI) or the 4K score may be used, while Progensa PCA3 may be measured to reduce the number of repeat biopsies in men with a previously negative biopsy. In addition to its role in screening, PSA is also widely used in the management of patients with diagnosed prostate cancer such as in surveillance following diagnosis, monitoring response to therapy and in combination with both clinical and histological criteria in risk stratification for recurrence. For determining aggressiveness and predicting outcome, especially in low- or intermediate-risk men, tissue-based multigene tests such as Decipher, Oncotype DX (Prostate), Prolaris and ProMark, may be used. Emerging therapy predictive biomarkers include AR-V7 for predicting lack of response to specific anti-androgens (enzalutamide, abiraterone), BRAC1/2 mutations for predicting benefit from PARP inhibitor and PORTOS for predicting benefit from radiotherapy. With the increased availability of multiple biomarkers, personalised treatment for men with prostate cancer is finally on the horizon.

Multicenter Evaluation of the Performance and Clinical Utility in Longitudinal Monitoring of the Bayer Immuno 1™ Complexed PSA Assay

We conducted a multicenter evaluation of the analytical and clinical performance of the automated Bayer Immuno 1™ complexed PSA (cPSA) assay, and compared assay performance to the Bayer Immuno 1™ PSA assay. We sought to determine whether measurements of cPSA could be of clinical utility in the management of patients with prostate cancer. Results of the 10–day imprecision across three evaluation sites produced total CV < 2.50% and an analytical sensitivity of 0.02μg/L. There was an increased trend in clinical sensitivity for prostate cancer with increasing stage of disease (71–86%). Clinical specificity for patients with benign urogenital disease was 74.8%, and for other nonprostate diseases ranged from 91.1–100%. Retrospective serial monitoring of 155 patients with prostate cancer demonstrated concordance of cPSA measurements to clinical status for 97% of the patients analyzed. Results from the clinical studies using the Bayer Immuno 1 cPSA assay were comparable to results obtained with the Bayer Immuno 1 PSA assay. The Bayer Immuno 1 cPSA assay demonstrates analytical performance and clinical effectiveness in the management of prostate cancer patients during the course of disease and therapy.

Five-Year Stability Study of Free and Total Prostate-Specific Antigen Concentrations in Serum Specimens Collected and Stored at – 70°C or Less

The stability of total (t) and free (f) prostate-specific antigen (PSA) in male serum specimens stored at –70°C or lower temperature for 4.7 to 4.9 years was studied. Until now, the stability of these analytes in serum has not been evaluated systematically beyond 2 years of storage at –70°C. Aliquots of frozen serum were thawed in 2001 and 2006 and assayed for tPSA and fPSA using a Dade Behring Dimension(r) RxL analyzer and reagents. tPSA values ranged from 0.07 to 69.94 and 0.00 to 69.83 ng/mL in 2001 and 2006, respectively, whereas fPSA values for the tested specimens ranged from 0.02 to 5.72 and 0.00 to 5.92, respectively. Deming regression analyses showed agreement in assay values over time as tPSA values yielded a slope of 1.0112 and a y-intercept of 0.0195; fPSA values produced a slope 1.0538 and a y-intercept of –0.0442; f/tPSA values yielded a slope of 0.9631 and a y-intercept of 0.1195. A Bland-Altman analysis of the data demonstrated analyte and ratio stability over this time period. We conclude that serum, when collected properly and stored at –70°C or lower temperature, may be used for tPSA and fPSA clinical studies for at least 5 years after collection.

Fifteen-year mortality after radical prostatectomy: which factors are available for patient counselling?

OBJECTIVE

The aims of this study were to establish 15-year postprostatectomy prostate cancer-specific mortality (PCSM), explore the time to prostate-specific antigen (PSA) relapse and identify clinically available prognostic factors.

MATERIAL AND METHODS

From 1987 to 2004, 309 men (median age 62 years, range 40-74 years) were prostatectomized for localized prostate cancer at a tertiary referral cancer centre. Slightly modified D'Amico risk groups were identified. PSA relapse was defined as PSA ≥ 4 μg/l before 2000, and thereafter as PSA > 0.2 μg/l. Radical prostatectomy (RP) 3-12 months after diagnosis represented "deferred" RP. PCSM was assessed with competing risk modelling. The level of significance was set at p < 0.05.

RESULTS

After a median of 12 years, 41 men were dead from prostate cancer and 68 due to other causes [15-year PCSM 15%, 95% confidence interval (CI) 10-19%], with no significant difference in PCSM between the low- and intermediate-risk groups, and the "conventional" high-risk group having 24% PCSM (95% CI 16-32%). PCSM was 33% (95% CI 20-46%) for men with two high-risk factors. The median time to PSA relapse (n = 152) was 5 (range 0-17) years, with a median of 7 (range 0-17) years' survival thereafter. Deferral of RP for up to 1 year had no impact on PCSM for all patients combined.

CONCLUSIONS

Approximately one in seven men with localized prostate cancer, prostatectomized before the PSA era, will die from the disease within the 15 years post-RP. Men with two high-risk criteria have a particularly poor prognosis. After PSA relapse the median survival is 7 years. The data on deferral of RP need confirmation, taking into account risk group allocation.

Early Detection of Cancer: Immunoassays for Plasma Tumor Markers

BACKGROUND: Plasma tumor biomarkers are widely used clinically for monitoring response to therapy and detecting cancer recurrence. However, only a limited number of them have been effectively used for the early detection of cancer. OBJECTIVE: To review plasma tumor markers used clinically for the early detection of cancer and to provide expert opinion about future directions. METHODS: Literature review, as well as our expert opinion, of plasma tumor markers that have been widely accepted for the early detection of cancer. RESULTS: In the United States, only prostate specific antigen (PSA), cancer antigen 125 (CA125), and alpha-fetoprotein (AFP) have been clinically used for the early detection of prostate, ovarian, and liver cancers, respectively. Both analytical and clinical issues related to the use of these three markers were discussed. CONCLUSION: Few plasma tumor markers have been used effectively for the early detection of cancer, mainly due to their limited sensitivity and/or specificity. Multiple approaches have been developed to improve the clinical performance of tumor markers for the early detection of cancer. Metrological traceability and antibody specificity are important issues to ensure comparability of immunoassays for the measurement of plasma tumor markers.

Disseminated tumor cells in bone marrow following definitive radiotherapy for intermediate or high-risk prostate cancer

BACKGROUND

The purpose of this study was to explore the prevalence of disseminated tumor cells (DTCs) in bone marrow (BM) of clinically progression-free prostate cancer (PC) patients at least 2 years after curatively intended radiotherapy (RT) with or without adjuvant hormone treatment.

METHODS

All patients were T(1-3)N(0)M(0) with intermediate or high risk of progression. Median time from RT to BM sampling was 5 years (2-8). A standardized immunocytochemical method applying the anticytokeratin antibodies AE1/AE3 was used for DTCs detection in 130 patients. Morphological characterization of immunostained cells was performed to exclude false positive cells. The post-treatment BM was explored in relation to pre-treatment risk factors, treatment strategy and serum levels of Testosterone and PSA at the time of BM sampling. Longitudinal changes in BM status were studied in a sub-group of 109 patients who also had donated BM prior to treatment.

RESULTS

Post-treatment BM-aspirates were positive for DTCs in 17% of cases without correlation to any of the tested variables. Out of 14 patients who had DTCs in BM prior to treatment, all but one had become post-treatment negative. Out of 95 patients with pre-treatment negative BM status, 18 (19%) had become post-treatment positive.

CONCLUSIONS

DTCs in BM were found in 17% of clinically progression-free PC patients following RT. The detection of these cells may provide PSA-independent prognostic information remaining to be explored by prolonged follow-up.

The value of (−7, −5)pro-prostate-specific antigen and human kallikrein-2 as serum markers for grading prostate cancer

OBJECTIVE

To assess the value of the precursor form (-7,5pro) of prostate-specific antigen (PSA) and human kallikrein-2 (hK2) for detecting and grading prostate cancer, as better serum markers with improved specificity are needed in men with lower ranges of total (t)PSA.

PATIENTS AND METHODS

tPSA, free PSA (fPSA), the precursor (-7,5)proPSA and hK2 were measured in a subset of participants of the European Randomised Study of Screening of Prostate Cancer. In a pilot study, sera from 143 men biopsied but with no prostate cancer, 142 with BPH, and 146 with prostate cancer were analysed to determine the relative value of serum markers for differentiating between the groups. Then, in 141 men with prostate cancer who had a radical prostatectomy, these serum markers were related to the pathological grading to analyse their value as prognostic variables.

RESULTS

Levels of (-7,5)proPSA, hK2 and fPSA could be used to distinguish between BPH and cancer, but proPSA and hK2, alone or combined, did not improve the specificity of fPSA for discriminating BPH and cancer. There was also no correlation between these serum markers and pathological tumour grade.

CONCLUSION

The clinical effect of using (-7,5)proPSA or hK2 for detecting and grading prostate cancer remains limited.

Neuroendocrine serum tumour markers in hormone-resistant prostate cancer

OBJECTIVE

The primary aim of the study was to assess the prevalence of elevated serum levels of neuron-specific enolase (NSE) and chromogranin A (CgA) in hormone-resistant prostate cancer (HRPC), and to evaluate these markers' prognostic significance. Secondarily we wanted to assess any change in serum levels of NSE or CgA after palliative radiotherapy.

METHODS

Serum samples from patients with painful bone metastases or symptomatic pelvic tumours due to HRPC were analyzed for prostate specific antigen (PSA), NSE and CgA before and after palliative radiotherapy.

RESULTS

Forty-six of 138 patients (33%) had elevated NSE before radiotherapy, while 80 (58%) had elevated CgA, without correlation between the two markers or with PSA. After radiotherapy the median NSE level was significantly reduced (p=0.004), whereas CgA (p=0.009) and PSA (p=0.019) increased. In the multivariate survival analysis, a reduced performance status, >20 bone metastases on bone scan, low hemoglobin, and pre-radiotherapy elevated NSE levels indicated a short survival.

CONCLUSION

Together with known clinical parameters, NSE predicts survival in patients with HRPC. NSE could become a valuable prognostic marker in patients with this condition.

Evaluation of the clinical performance of equimolar- and skewed-response total prostate-specific antigen assays versus complexed and free PSA assays and their ratios in discriminating between benign prostatic hyperplasia and prostate cancer

BACKGROUND

Prostate-specific antigen (PSA) exists in human serum in two principal forms, free PSA (fPSA) and protein-complexed PSA, predominantly PSA-ACT (alpha(1)-antichymotrypsin). Equimolar response (EMR) total PSA (tPSA) immunoassays measure each of these forms equally while skewed-response (SKR) assays overestimate or underestimate the tPSA concentration. The advantages of EMR over SKR tPSA assays are controversial.

METHODS

We used five nonhuman serum-based samples each containing a different proportion of fSPA:PSA-ACT (0:100 to 100:0, %:%) and patients' serum samples from men with histologically confirmed benign prostatic hyperplasia (BPH) (n=94) or PCA (n=30) and a wide range of fPSA concentrations to investigate the molar response status of six tPSA assays. Receiver-operator characteristic (ROC) curve analysis was used to compare the discriminatory power of these assays in distinguishing men with BPH from those with PCA.

RESULTS

The Bayer Immuno-1 tPSA (BtPSA) assay demonstrated EMR characteristics and diagnostic accuracy similar to the Hybritech Tandem-E and Tandem-R tPSA assays. At 90% sensitivity, EMR tPSA assays had higher specificity than SKR tPSA assays.

CONCLUSIONS

The BtPSA assay is an EMR tPSA assay and EMR assays provide improved diagnostic specificity over SKR tPSA assays.

Short-term stability of the molecular forms of prostate-specific antigen and effect on percent complexed prostate-specific antigen and percent free prostate-specific antigen

Differences in stability of the free and complexed molecular forms of prostate-specific antigen (PSA) may influence the clinical utility of assays for these forms, as well as the calculated ratios to total PSA (tPSA), such as percent free PSA (fPSA) and percent complexed PSA (cPSA). The objective of this study was to directly compare the short-term stability of fPSA and cPSA under different storage conditions. Specimens (3 with prostate cancer, 3 biopsy-negative without cancer, 2 normal) from 8 men were analyzed at baseline within 2 hours of collection, and at 4 hours, 8 hours, 24 hours, 48 hours, and 1 week after storage at room temperature, 4 degrees C, or -20 degrees C. Serum specimens were analyzed in duplicate on the Bayer Immuno 1 analyzer (tPSA, cPSA) and on the Beckman Coulter Access analyzer (tPSA, fPSA Tandem assays). Baseline tPSA values ranged from 0.7 to 62.0 ng/mL, with a median of 7.9 ng/mL (Immuno 1). Overall, all forms of PSA were stable up to 24 hours at the 3 temperatures, with the exception of fPSA and percent fPSA, which decreased when stored at 4 degrees C. After 1 week, tPSA levels decreased when stored at room temperature and at 4 degrees C, as did cPSA stored at room temperature. Over the 7 days, percent cPSA was stable at room temperature, but increased at 4 degrees C. There were no significant changes in any PSA form or calculated ratio with storage at -20 degrees C for up to 1 week. In summary, in the short term (<1 week), fPSA is less stable with storage than tPSA or cPSA in a time- and temperature-dependent fashion. Thus, specimen handling should be considered when interpreting PSA results. It is recommended that specimens not analyzed the same day (within 8 hours of collection) be stored frozen at -20 degrees C.

No association of serum gonadal or pituitary hormones with prognostic parameters in stages T1 to T3 PN0M0 prostate cancer

PURPOSE

Recent reports suggest a possible association of the clinical aggressiveness of prostate cancer with low serum testosterone, and high serum levels of lutenizing hormone (LH) and/or follicle-stimulating hormone (FSH). This hypothesis was tested in the current study.

MATERIALS AND METHODS

Serum levels of testosterone, LH, FSH, estradiol and sex hormone-binding globulin were determined as well as the calculated ratio of testosterone-to-sex hormonebinding globulin in 370 patients with newly diagnosed, stages T1 to T3 pN0M0 prostate cancer. The results were related to T category, Gleason score and serum prostate specific antigen (PSA).

RESULTS

No statistically significant association was found for the serum levels of testosterone, LH, FSH, estradiol, sex hormone-binding globulin or the testosterone-to-sex hormone-binding globulin ratio with T category, Gleason score or PSA. In contrast to expectations, serum testosterone values within the lowest quartile were not associated with elevated LH. Of the 370 patients 17 (5%) had serum testosterone below the normal range (8 nmol./l. or less) and only 3 of these 17 showed elevated LH levels.

CONCLUSIONS

Serum levels reflecting the pituitary-gonadal axis at diagnosis are not associated with clinically used measures of tumor aggressiveness (T category, Gleason score or PSA) in patients with newly diagnosed T1 to T3 pN0M0 prostate cancer.

Amperometric biosensors for detection of the prostate cancer marker (PSA)

Prostate specific antigen (PSA) has been identified as the most reliable clinical tool for diagnosing and monitoring prostate cancer (CAP). Since, there is no curative therapy available for prostate cancer, detecting the disease at the early stage is the best hope of increasing mortality rate. There are some procedures available for the detection of prostate cancer e.g. Tandem-R PSA, Hybritech Inc. (USA), IMx-PSA Abbott Laboratories (USA). However, these are time consuming and costly. We have developed a very simple and cost effective technique for identification and monitoring of prostate cancer using amperometric immunosensor. PSA is a glycoprotein with 93% peptide and 7% sugar content and isoelectric pH of 6.9. It may exist in the human serum as free (f-PSA) and complex (PSA-ACT) forms. Normally if the total PSA (t-PSA) level is more than 10 ng/ml, CAP is suspected. This paper presents an amperometric detection procedure for t-PSA using three electrode system in which working electrode (WE) is made of hydroxyethyl cellulose (HEC) and rhodinised carbon. The method used is rapid, very easy to use and involves low cost compared with other procedures. The electrochemical response was directly observed due to enzymatic reaction via a sandwich immunoassay on the WE. Monoclonal capture antibody (Mab) to PSA was immobilised on the WE and the other Mab labelled by the enzyme marker, horseradish peroxidase (HRP), was used as a tracer antibody.

Independent prognostic significance of HER-2 oncoprotein expression in pN0 prostate cancer undergoing curative radiotherapy

Existing prognostic algorithms for localized prostate cancer (PC) are hampered by poor validation for endpoints other than biochemical relapse such as clinical disease progression or survival. Therefore, the prognostic relevance of Her-2 (Her-2/neu, c-erbB2) protein expression in patients undergoing curative radiotherapy (RT) was compared to widely accepted prognostic factors such as pretreatment prostate-specific antigen (PSA) levels, biopsy Gleason score and T category of the primary tumor. Biopsies from 112 homogeneously treated patients with T1-4pN0M0 PC were examined by immunohistochemistry and 37% of cases showed membrane-bound Her-2 expression in more than 10% of cancer cells. No definite membrane staining was seen in normal prostate epithelium. With 25 patients dead of PC and a median follow-up of surviving patients of 71 months (range 48-144), the prognostic relevance of Her-2 expression was univariately associated with adverse outcome in terms of biochemical or clinical progression-free survival (B/C-PFS; p = 0.04), clinical progression-free survival (C-PFS; p = 0.02) and disease-specific survival (DSS; p = 0.02). In multivariate analysis, Her-2 expression, T category and Gleason score were independently associated with C-PFS, whereas only Her-2 expression and Gleason score were associated with DSS. Her-2 expression and Gleason score together discriminated 2 groups of patients with 5-year DSS of 95% and 79%, respectively (p < 0.001). Pretreatment PSA levels were associated only with B/C-PFS but not with C-PFS or DSS. Together the data show for the first time that expression of Her-2 is of prognostic relevance in localized PC undergoing RT and suggest that analysis for Her-2 may improve prognostic algorithms for clinically relevant endpoints other than biochemical relapse.

Prognostic value of neuroendocrine serum markers and PSA in irradiated patients with pN0 localized prostate cancer

BACKGROUND

The prognosis of patients with localized prostate cancer depends on clinical stage, histological grade, and pretreatment prostate-specific antigen (PSA). We evaluated the additional prognostic impact of serum levels of neuron-specific enolase (NSE) and chromograninA (CgA) after curative radiotherapy and the importance of serum PSA, analyzed 3 months after irradiation.

METHODS

From 1988 to 1995, 161 patients with localized T1-4, pN0M0, prostate adenocarcinoma were treated with external radiation (66Gy, 2Gy/5 fractions per week). Frozen serum samples were assessed for CgA, NSE, and PSA before and 3 months after radiotherapy. CgA was analyzed in only 100 patients. NSE and CgA were determined by a immunometric assay. Total PSA was measured by a time-resolved fluoro-immunometric assay.

RESULTS

Prior to radiotherapy CgA was elevated in 16 of 100 patients, and NSE was elevated in 33 of the 161 patients. There was no association between grade, T category or pretreatment PSA and the levels of neuroendocrine markers. Pretreatment-elevated serum NSE, but not initial CgA, identified patients with an unfavorable prognosis. A < 50% reduction of PSA 3 months after radiotherapy was associated with decreased failure-free 10 years urvival. Multivariate analysis demonstrated an increased risk of failure for patients with elevated pretreatment NSE and PSA values, T3 category, and decline of PSA less than 50% 3 months after radiotherapy. The presence of none or several risk factors (1-4) defined clearly separable groups.

CONCLUSIONS

Together with T category and pretreatment serum PSA values, serum NSE values before radiotherapy and decrease of serum PSA 3 months after radiotherapy represent easily assessable prognostic parameters in patients undergoing curative radiation treatment for prostate cancer.

Different stability of free and complexed prostate-specific antigen in serum in relation to specimen handling and storage conditions

The effect of sample collection, storage conditions (time and temperature), and freeze-thaw cycles on the stability of free prostate-specific antigen (fPSA), PSA complexed with alpha1-antichymotrypsin (ACT-PSA), and total PSA (tPSA) in serum was studied. The analytes were quantified using immunoassays for tPSA and fPSA on the Elecsys system 2010 and a research assay for ACT-PSA on the ES system (Roche Diagnostics). The stability of the analytes was calculated as percentages of the values measured in samples 1 h after blood collection. When the samples were stored at 37 degrees C, at room temperature or at 4 degrees C, the stability of ACT-PSA was less impaired than that of fPSA. To avoid erroneous results in the determination of PSA isoforms and their corresponding ratios, serum samples should be preserved at 4 degrees C when the analysis is performed within 8 h after blood collection, or they should be stored at -80 degrees C if the analysis is not feasible during that period.

The immunohistochemical assessment of occult regional lymph node metastases in patients with T3pN0M0 prostate cancer before definitive radiotherapy

OBJECTIVE

To detect occult regional lymph node metastases in patients with T3pN0M0 prostate cancer not recognized by routine haematoxylin and eosin staining, and to evaluate the clinical relevance of this finding.

PATIENTS AND METHODS

Formalin-fixed and paraffin-embedded pelvic lymph nodes (1118) from 92 patients were evaluated by immunohistochemistry using antibodies for prostate specific antigen (PSA) and pancytokeratin (AE1/AE3). Of the tumours, 14% were well, 69% moderately and 17% poorly differentiated. The extent of tumour was categorized as T3pN0M0 in all patients, who were referred for definitive radiotherapy after pelvic staging lymphadenectomy. The median (range) serum PSA value before treatment was 18.5 (0.4-342) microg/L. After radiotherapy, the patients were followed by assessing biochemical progression, pelvic recurrence and/or development of distant metastases. The median (range) observation time for all patients was 61 (16-136) months.

RESULTS

Occult lymph node metastases were detected in four (4.4%) of the 92 patients. Patients with or without occult metastases had similar serum PSA levels and histological grades. None of the four patients with occult metastases progressed, compared with 37 of the 88 (42%) with no such metastases.

CONCLUSION

Using immunohistochemistry the detection rate of occult lymph node metastases in patients with T3pN0M0 prostate cancer is low. The occurrence of such metastases is probably unrelated to the serum PSA value before treatment. The short-term outcome of patients subsequently treated with definitive radiotherapy does not seem to be associated with the finding of occult lymph node metastases, but long-term follow-up is needed. So far, the results do not justify the search for occult lymph node metastases as a routine procedure in these patients

Prostate specific antigen and benign prostatic hyperplasia

Benign prostatic hyperplasia is a common condition in males over 50 years, but prostate cancer can develop in the same population. Prostate specific antigen, the best marker for prostate cancer, is also produced by benign epithelial cells, and there is an overlapping phenomenon between both conditions. The better we understand the relationships between benign prostatic hyperplasia and prostate specific antigen, the higher will be the discrimination power of prostate specific antigen measurement as a marker for prostate cancer. Our scope includes a review of the latest published material to date on this subject.