To assess the applicability of the Prostate Cancer Prevention Trial High Grade (Gleason grade ≥ 7) Risk Calculator (PCPTHG) in ten international cohorts, representing a range of populations.
25,512 biopsies from 10 cohorts (6 European, 1 UK, and 3 US) were included; 4 implemented 6-core biopsies and the remaining had 10- or higher schemes; 8 were screening cohorts and 2 were clinical. PCPTHG risks were calculated using prostate-specific antigen (PSA), digital rectal examination, age, African origin and history of prior biopsy and evaluated in terms of calibration plots, areas underneath the receiver operating characteristic curve (AUC), and net benefit curves.
The median AUC of the PCPTHG for high grade disease detection in the 10- and higher-core cohorts was 73.5% (range 63.9% to 76.7%) compared to a median of 78.1 (range = 72.0 to 87.6) among the four 6-core cohorts. Only the 10-core Cleveland Clinic cohort showed clear evidence of under-prediction by the PCPTHG, and this was restricted to risk ranges less than 15%. The PCPTHG demonstrated higher clinical net benefit in higher- compared to six-core biopsy cohorts, and among the former, there were no notable differences observed between clinical and screening cohorts, nor between European and US cohorts.
The PCPTHG requires minimal patient information and can be applied across a range of populations. PCPTHG risk thresholds ranging from 5 to 20%, depending on patient risk averseness, are recommended for clinical prostate biopsy decision-making.
Calibration; Discrimination; Net Benefit; High Grade Prostate Cancer; Risk; Prostate Cancer Prevention Trial
Circulating tumor cells (CTC) are shed in peripheral blood at advanced metastatic stages of solid cancers. Surface-marker-based detection of CTC predicts recurrence and survival in colorectal, breast, and prostate cancer. However, scarcity and variation in size, morphology, expression profile, and antigen exposure impairs reliable detection and characterization of CTC. We have developed a non-contact, label-free microfluidic acoustophoresis method to separate prostate cancer cells from white blood cells (WBC) through forces generated by ultrasonic resonances in microfluidic channels. Implementation of cell pre-alignment in a temperature-stabilized (±0.5°C) acoustophoresis microchannel dramatically enhanced the discriminatory capacity and enabled the separation of 5-μm microspheres from 7-μm microspheres with 99% purity. Next, we determined the feasibility of employing label-free microfluidic acoustophoresis to discriminate and divert tumor cells from WBCs using erythrocyte-lysed blood from healthy volunteers spiked with tumor cells from three prostate cancer cell-lines (DU145, PC3, LNCaP). For cells fixed with paraformaldehyde, cancer cell recovery ranged from 93.6% to 97.9% with purity ranging from 97.4% to 98.4%. There was no detectable loss of cell viability or cell proliferation subsequent to the exposure of viable tumor cells to acoustophoresis. For non-fixed, viable cells, tumor cell recovery ranged from 72.5% to 93.9% with purity ranging from 79.6% to 99.7%. These data contribute proof-in-principle that label-free microfluidic acoustophoresis can be used to enrich both viable and fixed cancer cells from WBCs with very high recovery and purity.
Prostate cancer is a heterogenous disease with a variable natural history that is not accurately predicted by currently used prognostic tools.
We genotyped 798 prostate cancer cases of Ashkenazi Jewish ancestry treated for localized prostate cancer between June 1988 and December 2007. Blood samples were prospectively collected and de-identified before being genotyped and matched to clinical data. The survival analysis was adjusted for Gleason score and PSA. We investigated associations between 29 single nucleotide polymorphisms (SNPs) and biochemical recurrence, castration-resistant metastasis, and prostate cancer-specific survival. Subsequently, we performed an independent analysis using a high resolution panel of 13 SNPs.
On univariate analysis, 2 SNPs were associated (p<0.05) with biochemical recurrence; 3 SNPs were associated with clinical metastases; and 1 SNP was associated with prostate cancer-specific mortality. Applying a Bonferroni correction (p<0.0017), one association with biochemical recurrence (p=0.0007) was significant. Three SNPs showed associations on multivariable analysis, although not after correcting for multiple testing. The secondary analysis identified an additional association with prostate cancer-specific mortality in KLK3 (p<0.0005 by both univariate and multivariable analysis).
We identified associations between prostate cancer susceptibility SNPs and clinical endpoints. The rs61752561 in KLK3 and rs2735839 in the KLK2-KLK3 intergenic region associated strongly with prostate cancer-specific survival, and rs10486567 in 7JAZF1 gene associated with biochemical recurrence. A larger study will be required to independently validate these findings and determine the role of these SNPs in prognostic models.
Single nucleotide polymorphisms; Prostate cancer; Prognosis
The kallikrein gene family (KLK1-KLK15) is the largest contiguous group of protease genes within the human genome and is associated with both risk and outcome of cancer and other diseases. We searched for copy number variants in all KLK genes using quantitative PCR analysis and analysis of inheritance patterns of single nucleotide polymorphisms. Two deletions were identified: one 2235-bp deletion in KLK9 present in 1.2% of alleles, and one 3394-bp deletion in KLK15 present in 4.0% of alleles. Each deletion eliminated one complete exon and created out-of-frame coding that eliminated the catalytic triad of the resulting truncated gene product, which therefore likely is a non-functional protein. Deletion breakpoints identified by DNA sequencing located the KLK9 deletion breakpoint to a long interspersed element (LINE) repeated sequence, while the deletion in KLK15 is located in a single copy sequence. To search for an association between each deletion and risk of prostate cancer (PC), we analyzed a cohort of 667 biopsied men (266 PC cases and 401 men with no evidence of PC at biopsy) using short deletion-specific PCR assays. There was no association between evidence of PC in this cohort and the presence of either gene deletion. Haplotyping revealed a single origin of each deletion, with most recent common ancestor estimates of 3000-8000 and 6000-14 000 years for the deletions in KLK9 and KLK15, respectively. The presence of the deletions on the same haplotypes in 1000 Genomes data of both European and African populations indicate an early origin of both deletions. The old age in combination with homozygous presence of loss-of-function variants suggests that some kallikrein-related peptidases have non-essential functions.
There is little consensus on a standard approach to analysing bone scan images. The Bone Scan Index (BSI) is predictive of survival in patients with progressive prostate cancer (PCa), but the popularity of this metric is hampered by the tedium of the manual calculation.
Develop a fully automated method of quantifying the BSI and determining the clinical value of automated BSI measurements beyond conventional clinical and pathologic features.
Design, setting, and participants
We conditioned a computer-assisted diagnosis system identifying metastatic lesions on a bone scan to automatically compute BSI measurements. A training group of 795 bone scans was used in the conditioning process. Independent validation of the method used bone scans obtained ≤3 mo from diagnosis of 384 PCa cases in two large population-based cohorts. An experienced analyser (blinded to case identity, prior BSI, and outcome) scored the BSI measurements twice. We measured prediction of outcome using pretreatment Gleason score, clinical stage, and prostate-specific antigen with models that also incorporated either manual or automated BSI measurements.
The agreement between methods was evaluated using Pearson’s correlation coefficient. Discrimination between prognostic models was assessed using the concordance index (C-index).
Results and limitations
Manual and automated BSI measurements were strongly correlated (ρ = 0.80), correlated more closely (ρ = 0.93) when excluding cases with BSI scores ≥10 (1.8%), and were independently associated with PCa death (p < 0.0001 for each) when added to the prediction model. Predictive accuracy of the base model (C-index: 0.768; 95% confidence interval [CI], 0.702–0.837) increased to 0.794 (95% CI, 0.727–0.860) by adding manual BSI scoring, and increased to 0.825 (95% CI, 0.754–0.881) by adding automated BSI scoring to the base model.
Automated BSI scoring, with its 100% reproducibility, reduces turnaround time, eliminates operator-dependent subjectivity, and provides important clinical information comparable to that of manual BSI scoring.
The use of acoustic forces to manipulate particles or cells at the microfluidic scale (i.e. acoustophoresis), enables non-contact, label-free separation based on intrinsic cell properties such as size, density and compressibility. Acoustophoresis holds great promise as a cell separation technique in several research and clinical areas. However, it has been suggested that the force acting upon cells undergoing acoustophoresis may impact cell viability, proliferation or cell function via subtle phenotypic changes. If this were the case, it would suggest that the acoustophoresis method would be a less useful tool for many cell analysis applications as well as for cell therapy.
We investigate, for the first time, several key aspects of cellular changes following acoustophoretic processing. We used two settings of ultrasonic actuation, one that is used for cell sorting (10 Vpp operating voltage) and one that is close to the maximum of what the system can generate (20 Vpp). We used microglial cells and assessed cell viability and proliferation, as well as the inflammatory response that is indicative of more subtle changes in cellular phenotype. Furthermore, we adapted a similar methodology to monitor the response of human prostate cancer cells to acoustophoretic processing. Lastly, we analyzed the respiratory properties of human leukocytes and thrombocytes to explore if acoustophoretic processing has adverse effects.
BV2 microglia were unaltered after acoustophoretic processing as measured by apoptosis and cell turnover assays as well as inflammatory cytokine response up to 48 h following acoustophoresis. Similarly, we found that acoustophoretic processing neither affected the cell viability of prostate cancer cells nor altered their prostate-specific antigen secretion following androgen receptor activation. Finally, human thrombocytes and leukocytes displayed unaltered mitochondrial respiratory function and integrity after acoustophoretic processing.
We conclude that microchannel acoustophoresis can be used for effective continuous flow-based cell separation without affecting cell viability, proliferation, mitochondrial respiration or inflammatory status.
This study investigated the feasibility of targeting the free, unbound forms of prostate-specific antigen (fPSA) for in vivo imaging of prostate adenocarcinomas (PCa), as PSA is produced and secreted at abundance during every clinical stage and grade of PCa, including castration-resistant disease. We injected 125I-labeled monoclonal antibody PSA30 (specific for an epitope uniquely accessible on fPSA alone) intravenously in male nude mice carrying subcutaneous xenografts of LNCaP tumors (n=36). Mice were sacrificed over a time course from 4 hours to 13 days after injecting 125I-labeled PSA30. Tissue uptake of 125I-PSA30 at 48 and 168 hours after intravenous injection was compared with two clinically used positron emission tomography radiopharmaceuticals, 18F-fluoro-deoxy-glucose (18F-FDG) or 18F-choline, in cryosections using Digital AutoRadiography (DAR) and also compared with immunohistochemical staining of PSA and histopathology. On DAR, the areas with high 125I-PSA30 uptake corresponded mainly to morphologically intact and PSA-producing LNCaP cells, but did not associate with the areas of high uptake of either 18F-FDG or 18F-choline. Biodistribution of 125I-PSA30 measured in dissected organs ex vivo during 4 to 312 hours after intravenous injection demonstrated maximum selective tumor uptake 24–48 hours after antibody injection. Our data showed selective uptake in vivo of a monoclonal antibody highly specific for fPSA in LNCaP cells. Hence, in vivo imaging of fPSA may be feasible with putative usefulness in disseminated PCa.
digital autoradiography; dual isotope imaging; free PSA; prostate cancer; prostate-specific antigen; radioimmunodetection
To evaluate the discrimination, calibration and net benefit performance of the Prostate Cancer Prevention Trial Risk Calculator (PCPTRC) across five European Randomized study of Screening for Prostate Cancer (ERSPC), 1 United Kingdom, 1 Austrian and 3 US biopsy cohorts.
PCPTRC risks were calculated for 25,733 biopsies using prostate-specific antigen (PSA), digital rectal examination, family history and history of prior biopsy, and single imputation for missing covariates. Predictions were evaluated using the areas underneath the receiver operating characteristic curves (AUC), discrimination slopes, chi-square tests of goodness of fit, and net benefit decision curves.
AUCs of the PCPTRC ranged from a low of 56% in the ERSPC Goeteborg Rounds 2-6 cohort to a high of 72% in the ERSPC Goeteborg Round 1 cohort, and were statistically significantly higher than that of PSA in 6 out of the 10 cohorts. The PCPTRC was well-calibrated in the SABOR, Tyrol and Durham cohorts. There was limited to no net benefit to using the PCPTRC for biopsy referral compared to biopsying all or no men in all five ERSPC cohorts and benefit within a limited range of risk thresholds in all other cohorts.
External validation of the PCPTRC across ten cohorts revealed varying degree of success highly dependent on the cohort, most likely due to different criteria for and work-up before biopsy. Future validation studies of new calculators for prostate cancer should acknowledge the potential impact of the specific cohort studied when reporting successful versus failed validation.
receiver operating characteristic curve; risk; prostate cancer; calibration; net benefit
Despite intense efforts to develop radiotracers to detect cancers or monitor treatment response, few are widely used due to challenges with demonstrating clear clinical utility. We reasoned that a radiotracer targeting a validated clinical biomarker could more clearly assess the advantages of imaging cancer. The virtues and shortcomings of measuring secreted prostate specific antigen (PSA), an androgen receptor (AR) target gene, in prostate cancer (PCa) patients are well documented, making it a logical candidate for assessing whether a radiotracer can reveal new (and useful) information beyond that conferred by serum PSA. Therefore, we developed 89Zr-5A10, a novel radiotracer that targets “free” PSA. 89Zr-5A10 localizes in an AR-dependent manner in vivo to models of castration resistant prostate cancer, a disease state where serum PSA may not reflect clinical outcomes. Finally, we demonstrate that 89Zr-5A10 can detect osseous PCa lesions, a context where bone scans fail to discriminate malignant and non-malignant signals.
PET; prostate cancer; prostate specific antigen; androgen receptor; biomarker; PSA; PCa; AR; CRPC; 18F-FDG; fPSA; mAbs; PET; MRI; PSMA; ITLC
Although case-control studies have identified numerous single nucleotide polymorphisms (SNPs) associated with prostate cancer, the clinical role of these SNPs remains unclear.
Evaluate previously identified SNPs for association with prostate cancer and accuracy in predicting prostate cancer in a large prospective population-based cohort of unscreened men.
Design, setting, and participants
This study used a nested case-control design based on the Malmö Diet and Cancer cohort with 943 men diagnosed with prostate cancer and 2829 matched controls. Blood samples were collected between 1991 and 1996, and follow-up lasted through 2005.
We genotyped 50 SNPs, analyzed prostate-specific antigen (PSA) in blood from baseline, and tested for association with prostate cancer using the Cochran-Mantel-Haenszel test. We further developed a predictive model using SNPs nominally significant in univariate analysis and determined its accuracy to predict prostate cancer.
Results and limitations
Eighteen SNPs at 10 independent loci were associated with prostate cancer. Four independent SNPs at four independent loci remained significant after multiple test correction (p < 0.001). Seven SNPs at five independent loci were associated with advanced prostate cancer defined as clinical stage ≥T3 or evidence of metastasis at diagnosis. Four independent SNPs were associated with advanced or aggressive cancer defined as stage ≥T3, metastasis, Gleason score ≥8, or World Health Organization grade 3 at diagnosis. Prostate cancer risk prediction with SNPs alone was less accurate than with PSA at baseline (area under the curve of 0.57 vs 0.79), with no benefit from combining SNPs with PSA. This study is limited by our reliance on clinical diagnosis of prostate cancer; there are likely undiagnosed cases among our control group.
Only a few previously reported SNPs were associated with prostate cancer risk in the large prospective Diet and Cancer cohort in Malmö, Sweden. SNPs were less useful in predicting prostate cancer risk than PSA at baseline.
Prostate cancer; Biomarkers; SNPs; PSA; Sensitivity and specificity
Prostate specific antigen (PSA) is a widely used and clinically valuable marker for prostate disease. In order to enable the development of new PSA assays and progress the understanding of the biology of PSA we have analyzed PSA in seminal plasma.
Design and Methods
PSA in seminal plasma from men attending a fertility clinic and healthy controls was analyzed using SDS-PAGE, Western blotting and mass spectrometry.
Using mass spectrometry, different forms of PSA could be identified in 1–9 bands seen on SDS-PAGE analysis of the respective sample. However, a majority of these molecular forms of PSA were not observed on Western blots. Enzymatic activity of PSA isoforms was demonstrated by sequencing data in zymogram gels. Multivariate analysis of clinical data revealed well-separated patient groups.
We demonstrated that PSA in seminal plasma occurs in several isoforms, yet not all were detectable using an antibody based clinical routine method. The heterogeneity of PSA expression might be of clinical significance, by an improved patient phenotyping.
prostate specific antigen; isoform; seminal plasma; infertility; MALDI LTQ Orbitrap XL; ESI-LTQ FT-ICR
To assess variation of total prostate-specific antigen (tPSA), free PSA (fPSA), percent fPSA, human glandular kallikrein 2 (hK2), and intact PSA measured three times within two weeks. Knowledge of the variation in an individual’s PSA level is important for clinical decision-making.
Patients and Methods
Study participants were 149 patients referred for prostate biopsy, of which 97 had benign disease and 52 had prostate cancer. Three blood samples were drawn with a median of four hours between first and second samples and 12 days between first and third samples. Variability was described by absolute differences, ratios and intra-individual coefficients of variation. Total PSA, fPSA, hK2, and intact PSA were measured in anti-coagulated blood plasma.
At baseline, the median tPSA was 6.8 (IQR 4.5, 9.6) ng/mL. The intra-individual variation was low for all biomarkers, and lowest for tPSA. For 80% of participants, the ratio between first and second time points for tPSA was between 0.91 and 1.09 and the ratio for percent fPSA was between 0.89 and 1.15. Total coefficients of variation between time 1 and 2 for tPSA, fPSA, percent fPSA, hK2 and intact PSA were 4.0%, 6.6%, 6.0%, 9.2%, and 9.5%, respectively. The measurements taken several days apart varied more than those taken on the same day, but the variation between both time points were not large.
The intra-individual variation for all the kallikrein-like markers studied was relatively small, especially for samples drawn the same day. Few cases are reclassified between the time points. This indicates high short-term biological and technical reproducibility of the tests in clinical use.
Free PSA; Prostate cancer; PSA; Screening; Variation
The introduction of total prostate specific antigen (total PSA) testing in blood has revolutionized the detection and management of men with prostate cancer (PCa). The objective of this review was to discuss the challenges of PCa biomarker research, definition of the type of PCa biomarkers, the statistical considerations for biomarker discovery and validation, and to review the literature regarding total PSA velocity and novel blood-based biomarkers.
An English-language literature review of the Medline database (1990 to August 2010) of published data on blood-based biomarkers and PCa was undertaken.
The inherent biological variability of total PSA levels affects the interpretation of any single result. Men who will eventually develop PCa have increased total PSA levels years or decades before the cancer is diagnosed. Total PSA velocity improves predictiveness of total PSA only marginally, limiting its value for PCa screening and prognostication. The combination of PSA molecular forms and other biomarkers improve PCa detection substantially. Several novel blood-based biomarkers such as human glandular kallikrein 2 (hK2), urokinase plasminogen activator (uPA) and its receptor (uPAR), transforming growth factor-beta 1 (TGF-β1); interleukin-6 (IL-6) and its receptor (IL-6R) may help PCa diagnosis, staging, prognostication, and monitoring. Panels of biomarkers that capture the biologic potential of PCa are in the process of being validated for PCa prognostication.
PSA is a strong prognostic marker for long-term risk of clinically relevant cancer. However, there is a need for novel biomarkers that aid clinical decision making about biopsy and initial treatment. There is no doubt that progress will continue based on the integrated collaboration of researchers, clinicians and biomedical firms.
Prostate neoplasms; molecular markers; prostate specific antigen
Percentage of free-to-total prostate-specific antigen (%fPSA) is an independent predictor of risk for prostate cancer among men with modestly elevated level of total PSA (tPSA) in blood. Physiological and pathological factors have been shown to influence the %fPSA value and diagnostic accuracy.
To evaluate genetic determinants of %fPSA, we conducted a genome-wide association study of serum %fPSA by genotyping 642,584 single nucleotide polymorphisms (SNPs) in 3192 men of European ancestry, each with a tPSA level of 2.5 to 10 ng/ml, that were recruited in the REduction by DUtasteride of Prostate Cancer Events study. Single nucleotide polymorphisms (SNPs) with P < 10-5 were further evaluated among the controls of a population-based case-control study in Sweden (2899 prostate cancer cases and 1722 male controls), including 464 controls having tPSA levels of 2.5 to 10 ng/ml.
We identified two loci that were associated with %fPSA at a genome-wide significance level (P <5 x 10-8). The first associated SNP was rs3213764 (P = 6.45 x 10-10), a nonsynonymous variant (K530R) in the ATF7IP gene at 12p13. This variant was also nominally associated with tPSA (P = .015). The second locus was rs1354774 (P = 1.25 x 10-12), near KLK2 at 19q13, which was not associated with tPSA levels, and is separate from the rs17632542 locus at KLK3 that was previously associated with tPSA levels and prostate cancer risk. Neither rs3213764 nor rs1354774 was associated with prostate cancer risk or aggressiveness.
These findings demonstrate that genetic variants at ATF7IP and KLK2 contribute to the variance of %fPSA.
Prostate specific antigen (PSA), as a widely used clinical biomarker in prostate cancer diagnostics, exists in multiple molecular forms. However, all of these forms might not be recognized in a given sample by the standard immunoassays. Therefore, we have investigated PSA isoforms separated by size using mass spectrometric analyses. The objective of these developments was to identify and specify the various forms of PSA. To optimize successful identification of different PSA forms, we have developed a bioinformatic strategy, consisting of high resolution MALDI-MS PMF and sequencing MS/MS data searches. To improve sequence-based identification, the recently introduced Proteios software environment was employed, allowing the combination of multiple database search engines in an automated manner.
We could unambiguously identify PSA in clinical samples by all detectable tryptic peptides, which were found to be common in several isoforms.
prostate specific antigen isoforms; MALDI LTQ Orbitrap XL; ESI-LTQ FT-ICR; Proteios software environment; kallikrein-2
Abiraterone acetate (AA) is an androgen biosynthesis inhibitor shown to prolong life in patients with castration-resistant prostate cancer (CRPC) already treated with chemotherapy. AA treatment results in dramatic declines in prostate-specific antigen (PSA) in some patients and no declines in others, suggesting the presence of molecular determinants of sensitivity in tumors.
To study the role of transmembrane protease, serine 2 (TMPRSS2)–v-ets erythroblastosis virus E26 oncogene homolog (ERG) fusion, an androgen-dependent growth factor, in circulating tumor cells (CTCs) as a biomarker of sensitivity to AA.
Design, setting, and participants
The predictive value of TMPRSS2-ERG status was studied in 41 of 48 men with postchemotherapy-treated CRPC enrolled in sequential phase 2 AA trials.
Patients received AA 1000 mg daily and continuously.
TMPRSS2-ERG status was characterized by a sensitive, analytically valid reverse transcription polymerase chain reaction assay in CTCs enriched from ethylene-diaminetetraacetic acid anticoagulated blood obtained prior to AA treatment. Outcomes were measured by PSA Working Group 1 criteria.
Results and limitations
Standard procedures for specimen acquisition, processing, and testing using the validated TMPRSS2-ERG assay on a multiplex platform gave intra-assay and interassay coefficients of variation <7%. TMPRSS2-ERG fusion was present in 15 of 41 patients (37%), who had a median baseline CTC count of 17 (interquartile range: 7–103 cells per 7.5 ml). A PSA decline ≥50% was observed in 7 of 15 patients (47%) with the fusion and in 10 of 26 patients (38%) without the fusion. Although limited by the low number of patients, a posttherapy CTC count of less than five per 7.5 ml was prognostic for longer survival relative to a CTC count five or more. TMPRSS2-ERG status did not predict a decline in PSA or other clinical outcomes.
Molecular profiles of CTCs with an analytically valid assay identified the presence of the prostate cancer–specific TMPRSS2-ERG fusion but did not predict for response to AA treatment. This finding demonstrates the role of CTCs as surrogate tissue that can be obtained in a routine practice setting.
Abiraterone; Biomarker; Circulating tumor cells; Prostate cancer; Prostate-specific antigen; TMPRSS2-ERG fusion
A sophisticated reading of the randomized trial evidence suggests that, although screening for prostate cancer with prostate-specific antigen (PSA) can reduce cancer-specific mortality, it does so at considerable cost in terms of the number of men who need to be screened, biopsied, and treated to prevent one death. The challenge is to design screening programs that maximize benefits (reducing prostate cancer mortality) and minimize costs (overtreatment). Recent research has suggested that this can be achieved by risk-stratifying screening and biopsy; increasing reliance on active surveillance for low-risk cancer; restricting radical prostatectomy to high-volume surgeons; and using appropriately high-dose radiotherapy. In current U.S. practice, however, many men who are screened are unlikely to benefit, most men found to have low-risk cancers are referred for unnecessary curative treatment, and much treatment is given at low-volume centers.
prostatic neoplasms; prostate-specific antigen (PSA); surgery; radiotherapy
Prostate specific antigen (PSA) velocity has been proposed as a marker to aid detection of prostate cancer. We sought to determine whether PSA velocity could predict the results of repeat biopsy in men with persistently elevated PSA after initial negative biopsy.
Materials and Methods
We identified 1,837 men who participated in the Göteborg or Rotterdam section of the European Randomized Screening study of Prostate Cancer (ERSPC), and who had one or more subsequent prostate biopsies after an initial negative finding. We evaluated whether PSA velocity improved predictive accuracy beyond that of PSA alone.
There were a total of 2579 repeat biopsies, of which 363 (14%) were positive for prostate cancer, and 44 (1.7%) were high grade (Gleason score ≥7). Although PSA velocity was statistically associated with cancer risk (p<0.001), it had very low predictive accuracy (area-under-the-curve [AUC] of 0.55). There was some evidence that PSA velocity improved AUC compared to PSA for high grade cancer. However, the small increase in risk associated with high PSA velocity – from 1.7 % to 2.8% as velocity increased from 0 to 1 ng / ml / year - is of questionable clinical relevance.
Men with a prior negative biopsy have a lower risk for prostate cancer at subsequent biopsies, with high grade disease particularly rare. We found little evidence to support the use of PSA velocity to aid decisions about repeat biopsy for prostate cancer.
We previously reported that a single prostate-specific antigen (PSA) measured at age 44–50 was highly predictive of subsequent prostate cancer diagnosis in an unscreened population. Here we report an additional seven years of follow-up. This provides a replication on an independent data set, and allows estimates of the association between early PSA and subsequent advanced cancer (clinical stage ≥T3 or metastases at diagnosis).
Blood was collected from 21,277 men in a Swedish city (74% participation rate) during 1974–1986 at age 33–50. Through 2006, prostate cancer was diagnosed in 1408 participants; we measured PSA in archived plasma for 1312 (93%) of these cases and for 3728 controls.
At a median follow-up of 23 years, baseline PSA was strongly associated with subsequent prostate cancer (area-under-the-curve 0.72; 95% CI 0.70, 0.74; for advanced cancer 0.75; 95% CI 0.72, 0.78). Associations between PSA and prostate cancer were virtually identical for the initial and replication data sets with 81% (95% CI 77%, 86%) of advanced cases found in men with PSA above the median (0.63 ng/ml at age 44 – 50).
A single PSA at or before age 50 predicts advanced prostate cancer diagnosed up to 30 years later. Use of early PSA to stratify risk would allow a large group of men to be screened less often but increase frequency of testing on a more limited number of high-risk men. This is likely to improve the ratio of benefits to harms for screening.
prostate cancer; prostate-specific antigen; human kallikrein 2; risk factors; case-control study
Evidence of reduced prostate cancer mortality from randomized trials in Europe supports early detection of prostate cancer with prostate-specific antigen (PSA). Yet PSA screening has generated considerable controversy: it is far from clear that the benefits outweigh risks, in terms of overdiagnosis and overtreatment. One way to shift the ratio of benefits to harms is to focus on men at highest risk, who have more to benefit than average. Neither family history nor any of the currently identified genomic markers offer sufficient risk stratification for practical use. However, there is considerable evidence that the levels of PSA in blood are strongly prognostic of the long-term risk of aggressive prostate cancer. Specifically, it is difficult to justify continuing to screen men age 60 or older if they have a PSA less than 1 or 2 ng/ml; for men 45 – 60, intervals between PSA tests can be based on PSA levels, with 2 to 4 year re-testing interval for men with PSA of 1 ng/ml or higher, and tests every 6 to 8 years for men with PSA < 1 ng/ml. Men with the top 10% of PSAs at a young age (PSA ~1.5 ng / ml or higher below 50) are at particularly high risk and should be subject to intensive monitoring.
prostatic neoplasms; early detection of cancer; prostate-specific antigen
Prostate-specific antigen (PSA) dynamics have been proposed to predict outcome in men with prostate cancer. We assessed the value of PSA velocity (PSAV) and doubling time (PSADT) for predicting prostate-cancer–specific mortality (PCSM) in men with clinically localized prostate cancer undergoing conservative management or early hormonal therapy. From 1990 to 1996, 2333 patients were identified, of whom 594 had two or more PSA values before diagnosis. We examined 12 definitions for PSADT and 10 for PSAV. Because each definition required PSA measurements at particular intervals, the number of patients eligible for each definition varied from 40 to 594 and number of events from 10 to 119. Four PSAV definitions, but no PSADT, were significantly associated with PCSM after adjustment for PSA in multivariable Cox proportional hazards regression. All 4 could be calculated only for a proportion of events, and the enhancements in predictive accuracy associated with PSAV had very wide confidence intervals. There was no clear benefit of PSAV in men with low PSA and Gleason grade 6 or less. Although evidence that certain PSAV definitions help predict PCSM in the cohort exist, the value of incorporating PSAV in predictive models to assist in determining eligibility for conservative management is, at best, uncertain.
prostate-specific antigen; prostate-specific antigen velocity; prostate-specific antigen doubling time; watchful waiting; prediction
Prostate specific antigen (PSA) is widely used for prostate cancer screening but its levels are influenced by many non cancer-related factors. The goal of the study is to estimate the effect of genetic variants on PSA levels.
We evaluated the association of SNPs that were reported to be associated with prostate cancer risk in recent genome-wide association studies with plasma PSA levels in a Swedish study population, including 1,722 control subjects without a diagnosis of prostate cancer.
Of the 16 SNPs analyzed in control subjects, significant associations with PSA levels (P≤0.05) were found for six SNPs. These six SNPs had a cumulative effect on PSA levels; the mean PSA levels in men were almost twofold increased across increasing quintile of number of PSA associated alleles, P-trend=3.4×10−14. In this Swedish study population risk allele frequencies were similar among T1c case patients (cancer detected by elevated PSA levels alone) as compared to T2 and above prostate cancer case patients.
Results from this study may have two important clinical implications. The cumulative effect of six SNPs on PSA levels suggests genetic-specific PSA cutoff values may be used to improve the discriminatory performance of this test for prostate cancer; and the dual associations of these SNPs with PSA levels and prostate cancer risk raise a concern that some of reported prostate cancer risk-associated SNPs may be confounded by the prevalent use of PSA screening.
genetic; bias; KLK3
The National Comprehensive Cancer Network and American Urological Association guidelines on early detection of prostate cancer recommend biopsy on the basis of high prostate-specific antigen (PSA) velocity, even in the absence of other indications such as an elevated PSA or a positive digital rectal exam (DRE).
To evaluate the current guideline, we compared the area under the curve of a multivariable model for prostate cancer including age, PSA, DRE, family history, and prior biopsy, with and without PSA velocity, in 5519 men undergoing biopsy, regardless of clinical indication, in the control arm of the Prostate Cancer Prevention Trial. We also evaluated the clinical implications of using PSA velocity cut points to determine biopsy in men with low PSA and negative DRE in terms of additional cancers found and unnecessary biopsies conducted. All statistical tests were two-sided.
Incorporation of PSA velocity led to a very small increase in area under the curve from 0.702 to 0.709. Improvements in predictive accuracy were smaller for the endpoints of high-grade cancer (Gleason score of 7 or greater) and clinically significant cancer (Epstein criteria). Biopsying men with high PSA velocity but no other indication would lead to a large number of additional biopsies, with close to one in seven men being biopsied. PSA cut points with a comparable specificity to PSA velocity cut points had a higher sensitivity (23% vs 19%), particularly for high-grade (41% vs 25%) and clinically significant (32% vs 22%) disease. These findings were robust to the method of calculating PSA velocity.
We found no evidence to support the recommendation that men with high PSA velocity should be biopsied in the absence of other indications; this measure should not be included in practice guidelines.
Prostate-specific antigen (PSA) has modest specificity for prostate cancer. A panel of four kallikrein markers (total, free, and intact PSA and kallikrein-related peptidase 2) is a highly accurate predictor of biopsy outcome. The clinical significance of biopsy-detectable cancers in men classified as low risk by this panel remains unclear.
The Malmö Diet and Cancer study is a population-based cohort of 11,063 Swedish men aged 45–73 providing a blood sample at baseline during 1991–1996. The Swedish Cancer Registry was used to identify 943men diagnosed with prostate cancer by 12/31/2006. PSA-testing was low. We assessed the predictive accuracy of our published statistical model to predict subsequent prostate cancer diagnosis in men with total PSA ≥3.0ng/mlat baseline.
Compared to total PSA and age, the full kallikrein panel enhanced the predictive accuracy for clinically diagnosed prostate cancer (concordance index 0.65 vs 0.75; p<0.001). For every 1000 men with total PSA≥3 ng/ml at baseline, the model would classify as high risk131/152 (86%)of the cancer cases diagnosed clinically within five years; 421men would be classified as low risk by the panel and recommended against biopsy. Of these, only 2would be diagnosed with advanced prostate cancer (clinical T3–T4 or metastases) within five years.
Men with PSA≥3 ng/ml but defined as low risk by the panel of four kallikrein markers are unlikely to develop incurable prostate cancer.
Use of the panel to determine referral to biopsy could substantially reduce the number of unnecessary prostate biopsies.
Prostate cancer; screening; PSA; prediction