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Molecular Form Differences Between Prostate-Specific Antigen (PSA) Standards Create Quantitative Discordances in PSA ELISA Measurements.

ABSTRACT: The prostate-specific antigen (PSA) assays currently employed for the detection of prostate cancer (PCa) lack the specificity needed to differentiate PCa from benign prostatic hyperplasia and have high false positive rates. The PSA calibrants used to create calibration curves in these assays are typically purified from seminal plasma and contain many molecular forms (intact PSA and cleaved subforms). The purpose of this study was to determine if the composition of the PSA molecular forms found in these PSA standards contribute to the lack of PSA test reliability. To this end, seminal plasma purified PSA standards from different commercial sources were investigated by western blot (WB) and in multiple research grade PSA ELISAs. The WB results revealed that all of the PSA standards contained different mass concentrations of intact and cleaved molecular forms. Increased mass concentrations of intact PSA yielded higher immunoassay absorbance values, even between lots from the same manufacturer. Standardization of seminal plasma derived PSA calibrant molecular form mass concentrations and purification methods will assist in closing the gaps in PCa testing measurements that require the use of PSA values, such as the % free PSA and Prostate Health Index by increasing the accuracy of the calibration curves.

SUBMITTER: McJimpsey EL

PROVIDER: S-EPMC4766849 | biostudies-other | 2016 Feb

REPOSITORIES: biostudies-other

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Project description:ObjectiveTo investigate the efficacy and safety of prostate-specific antigen (PSA) testing to screen for prostate cancer.DesignSystematic review and meta-analysis.Data sourcesElectronic search of Cochrane Central Register of Controlled Trials, Web of Science, Embase, Scopus, OpenGrey, LILACS, and Medline, and search of scientific meeting abstracts and trial registers to April 2018.Eligibility criteria for selecting studiesRandomised controlled trials comparing PSA screening with usual care in men without a diagnosis of prostate cancer.Data extractionAt least two reviewers screened studies, extracted data, and assessed the quality of eligible studies. A parallel guideline committee (BMJ Rapid Recommendation) provided input on the design and interpretation of the systematic review, including selection of outcomes important to patients. We used a random effects model to obtain pooled incidence rate ratios (IRR) and, when feasible, conducted subgroup analyses (defined a priori) based on age, frequency of screening, family history, ethnicity, and socioeconomic level, as well as a sensitivity analysis based on the risk of bias. The quality of the evidence was assessed with the GRADE approach.ResultsFive randomised controlled trials, enrolling 721?718 men, were included. Studies varied with respect to screening frequency and intervals, PSA thresholds for biopsy, and risk of bias. When considering the whole body of evidence, screening probably has no effect on all-cause mortality (IRR 0.99, 95% CI 0.98 to 1.01; moderate certainty) and may have no effect on prostate-specific mortality (IRR 0.96, 0.85 to 1.08; low certainty). Sensitivity analysis of studies at lower risk of bias (n=1) also demonstrates that screening seems to have no effect on all-cause mortality (IRR 1.0, 0.98 to 1.02; moderate certainty) but may have a small effect on prostate-specific mortality (IRR 0.79, 0.69 to 0.91; moderate certainty). This corresponds to one less death from prostate cancer per 1000 men screened over 10 years. Direct comparative data on biopsy and treatment related complications from the included trials were limited. Using modelling, we estimated that for every 1000 men screened, approximately 1, 3, and 25 more men would be hospitalised for sepsis, require pads for urinary incontinence, and report erectile dysfunction, respectively.ConclusionsAt best, screening for prostate cancer leads to a small reduction in disease-specific mortality over 10 years but has does not affect overall mortality. Clinicians and patients considering PSA based screening need to weigh these benefits against the potential short and long term harms of screening, including complications from biopsies and subsequent treatment, as well as the risk of overdiagnosis and overtreatment.Systematic review registrationPROSPERO registration number CRD42016042347.

Project description:PURPOSE:To evaluate the difference in prostate-specific antigen (PSA) recurrence-free, distant metastasis-free, overall, and cancer-specific survival between PSA bounce (PSA-B) and non-bounce patients treated with dose-escalated external beam radiation therapy (DE-EBRT). METHODS AND MATERIALS:During 1990-2010, 1898 prostate adenocarcinoma patients were treated with DE-EBRT to ≥75 Gy with ≥5 years follow-up. Patients receiving neoadjuvant/concurrent androgen-deprivation therapy (n=1035) or with fewer than 4 PSA values obtained 6 months or more after post-EBRT completion (n=87) were excluded. The evaluable 776 patients were treated (median, 81.0 Gy). Prostate-specific antigen bounce was defined as a ≥0.2-ng/mL increase above the interval PSA nadir, followed by a decrease to nadir or below. Prostate-specific antigen relapse was defined as post-radiation therapy PSA nadir + 2 ng/mL. Median follow-up was 9.2 years (interquartile range, 6.9-11.3 years). RESULTS:One hundred twenty-three patients (15.9%) experienced PSA-B after DE-EBRT at a median of 24.6 months (interquartile range, 16.1-38.5 months). On multivariate analysis, younger age (P=.001), lower Gleason score (P=.0003), and higher radiation therapy dose (P=.0002) independently predicted PSA-B. Prostate-specific antigen bounce was independently associated with decreased risk for PSA relapse (hazard ratio [HR] 0.53; 95% confidence interval [CI] 0.33-0.85; P=.008), distant metastatic disease (HR 0.34; 95% CI 0.12-0.94; P=.04), and all-cause mortality (HR 0.53; 95% CI 0.29-0.96; P=.04) on multivariate Cox analysis. Because all 50 prostate cancer-specific deaths in patients without PSA-B were in the non-bounce cohort, competing-risks analysis was not applicable. A nonparametric competing-risks test demonstrated that patients with PSA-B had superior cancer-specific survival compared with patients without PSA-B (P=.004). CONCLUSIONS:Patients treated with dose-escalated radiation therapy for prostate adenocarcinoma who experience posttreatment PSA-B have improved PSA recurrence-free survival, distant metastasis-free survival, overall survival, and cancer-specific survival outcomes.

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Molecular Form Differences Between Prostate-Specific Antigen (PSA) Standards Create Quantitative Discordances in PSA ELISA Measurements.

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