Charlotte Becker

Long-Term Prediction of Prostate Cancer Up to 25 Years Before Diagnosis of Prostate Cancer Using Prostate Kallikreins Measured at Age 44 to 50 Years

PURPOSE We examined whether prostate-specific antigen (PSA) forms and human kallikrein 2 (hK2) measured at age 44 to 50 years predict long-term risk of incident prostate cancer. METHODS From 1974 to 1986, 21,277 men age 50 years in Malmö, Sweden, enrolled onto a cardiovascular study (74% participation). The rate of PSA screening in this population is low. According to the Swedish Cancer Registry, 498 were later diagnosed with prostate cancer. We measured hK2, free PSA, and total PSA (tPSA) in archived blood plasma from 462 participants later diagnosed with prostate cancer and from 1,222 matched controls. Conditional logistic regression was used to test for association of prostate cancer with hK2 and PSA forms measured at baseline. RESULTS Median delay between venipuncture and prostate cancer diagnosis was 18 years. hK2 and all PSA forms were strongly associated with prostate cancer (all P < .0005). None of the 90 anthropometric, lifestyle, biochemical, and medical history variables measured at baseline was importantly predictive. A tPSA increase of 1 ng/mL was associated with an increase in odds of cancer of 3.69 (95% CI, 2.99 to 4.56); addition of other PSA forms or hK2 did not add to the predictive value of tPSA. tPSA remained predictive for men diagnosed > or = 20 years after venipuncture, and the predictive value remained unchanged in an analysis restricted to palpable disease. CONCLUSION A single PSA test at age 44 to 50 years predicts subsequent clinically diagnosed prostate cancer. This raises the possibility of risk stratification for prostate cancer screening programs.

Prostate-specific antigen at or before age 50 as a predictor of advanced prostate cancer diagnosed up to 25 years later: A case-control study

BackgroundBased on a large, representative unscreened cohort from Malmö, Sweden, we have recently reported that a single prostate-specific antigen (PSA) measurement at or before age 50 is a strong predictor of prostate cancer occurring up to 25 years subsequently. We aimed to determine whether this association holds for advanced cancers, defined as clinical stage T3 or higher, or skeletal metastasis at the time of the cancer diagnosis.MethodsIn 1974–1986 blood samples were obtained from a cohort of 21,277 men aged up to 50. Through 1999, 498 men were diagnosed with prostate cancer, and of these 161 had locally advanced or metastatic prostate cancers. Three controls, matched for age and date of venipuncture, were selected for each case. Conditional logistic regression was used to test associations between molecular markers and advanced cancer.ResultsMedian time from venipuncture to diagnosis was 17 years. Levels of all PSA forms and hK2 were associated with case status. Total PSA was a strong and statistically significant predictor of subsequent advanced cancer (area under the curve 0.791; p < 0.0005). Two-thirds of the advanced cancer cases occurred in men with the top 20% of PSA levels (0.9 ng/ml or higher).ConclusionA single PSA test taken at or before age 50 is a very strong predictor of advanced prostate cancer diagnosed up to 25 years later. This suggests the possibility of using an early PSA test to risk-stratify patients so that men at highest risk are the focus of the most intensive screening efforts.

DISCRIMINATION OF MEN WITH PROSTATE CANCER FROM THOSE WITH BENIGN DISEASE BY MEASUREMENTS OF HUMAN GLANDULAR KALLIKREIN 2 (HK2) IN SERUM

PURPOSE To investigate the clinical value of measuring human glandular kallikrein 2 (hK2) compared with free and total prostate specific antigen (PSA-F and PSA-T) in serum from patients with prostate disease. MATERIALS AND METHODS Serum from healthy controls, from men with benign prostate hyperplasia (BPH), clinically localized prostate cancer (PCa), and advanced PCa were analyzed for hK2 (using an in-house-research assay with detection limit of 0.05 ng./mL and <0.1% cross-reaction with PSA) and for PSA-F and PSA-T (using the Dual Prostatus assay from EG&G Wallac). RESULTS HK2 concentrations were <0.05 ng./mL in 50/50 healthy volunteers but significantly higher (p <0.0001) and > or =0.05 ng./mL in 28/54 (52%) patients with BPH. In comparison to these men, the hK2 levels were significantly higher (p <0.0001, median 0.085 ng./mL) and > or =0.05 ng./mL in 100/136 (74%) men with clinically localized PCa. Compared with localized PCa, the hK2 levels were significantly higher (p <0.0001, median 0.57 ng./mL) and > or =0.05 ng./mL in 55/57 (96%) patients with advanced PCa. The median hK2 levels ranged from 1.3 to 1.6% of those of PSA-T in all three patient groups, whereas percent hK2/PSA-F and hK2 x PSA-T/PSA-F levels were significantly higher in cancer patients compared with those with BPH. In the discrimination of clinically localized PCa from BPH, hK2 x PSA-T/PSA-F gave the largest area under the receiver operating curve (AUC = 0.81) and significantly (p = 0.025) larger AUC than PSA-T alone (0.70). Further, at 95% sensitivity there was significant gain in specificity, and at specificity levels of 90 to 95% there was significant gain in sensitivity using the measurements of PSA-T+PSA-F+hK2 compared with analysis of PSA-T and/or percent free PSA. CONCLUSIONS Discrimination of patients with benign prostate disease from those with prostate cancer was significantly enhanced using measurements of hK2 in addition to those of PSA-T and PSA-F. Percent hK2/PSA-F was higher in PCa than in BPH, a phenomena not yet understood.

Long-Term Prediction of Prostate Cancer: Prostate-Specific Antigen (PSA) Velocity Is Predictive but Does Not Improve the Predictive Accuracy of a Single PSA Measurement 15 Years or More Before Cancer Diagnosis in a Large, Representative, Unscreened Population

PURPOSE We tested whether total prostate-specific antigen velocity (tPSAv) improves accuracy of a model using PSA level to predict long-term risk of prostate cancer diagnosis. METHODS During 1974 to 1986 in a preventive medicine study in Sweden, 5,722 men aged <or= 50 gave two blood samples about 6 years apart. We measured free (fPSA) and total PSA (tPSA) in archived plasma samples from 4,907 participants. Prostate cancer was subsequently diagnosed in 443 (9%) men. Cox proportional hazards regression was used to evaluate tPSA and tPSAv as predictors of prostate cancer. Predictive accuracy was assessed by the concordance index. RESULTS The median time from second blood draw to cancer diagnosis was 16 years; median follow-up for men without prostate cancer was 21 years. In univariate models, tPSA level at second assessment and tPSAv between first and second assessments were associated with prostate cancer (both P < .001). tPSAv was highly correlated with tPSA level (r = 0.93). Twenty-year probabilities of cancer for men at 50th, 90th, and 95th percentile of tPSA and tPSAv were 10.6%, 17.1%, and 21.2% for tPSA, and 9.1%, 11.8%, and 14.1% for tPSAv, respectively. The concordance index for tPSA level was 0.771. Adding tPSAv, fPSA, %fPSA or velocities of fPSA and %fPSA did not importantly increase accuracy of tPSA to predict prostate cancer. Results were unchanged if the analysis was restricted to patients with advanced cancer at diagnosis. CONCLUSION Although PSA velocity is significantly increased in men with prostate cancer up to two decades before diagnosis, it does not aid long-term prediction of prostate cancer.

Summary Report of the TD-3 Workshop: Characterization of 83 Antibodies against Prostate-Specific Antigen

Twelve research groups participated in the ISOBM TD-3 Workshop in which the reactivity and specificity of 83 antibodies against prostate-specific antigen (PSA) were investigated. Using a variety of techniques including cross-inhibition assays, Western blotting, BIAcore, immunoradiometric assays and immunohistochemistry, the antibodies were categorized into six major groups which formed the basis for mapping onto two- and three-dimensional (2-D and 3-D) models of PSA. The overall findings of the TD-3 Workshop are summarized in this report. In agreement with all participating groups, three main antigenic domains were identified: free PSA-specific epitopes located in or close to amino acids 86–91; discontinuous epitopes specific for PSA without human kallikrein (hK2) cross-reactivity located at or close to amino acids 158–163; and continuous or linear epitopes shared between PSA and hK2 located close to amino acids 3–11. In addition, several minor and partly overlapping domains were also identified. Clearly, the characterization of antibodies from this workshop and the location of their epitopes on the 3-D model of PSA illustrate the importance of selecting appropriate antibody pairs for use in immunoassays. It is hoped that these findings and the epitope nomenclature described in this TD-3 Workshop are used as a standard for future evaluation of anti-PSA antibodies.

HUMAN GLANDULAR KALLIKREIN 2: A POTENTIAL SERUM MARKER FOR PREDICTING THE ORGAN CONFINED VERSUS NONORGAN CONFINED GROWTH OF PROSTATE CANCER

PURPOSE We measured serum levels of human glandular kallikrein 2 (hK2) in patients with prostate cancer treated with radical retropubic prostatectomy for clinically localized prostate cancer to determine whether preoperative hK2 levels discriminate stage pT2a/b from pathological stage T3a or greater cancer. This finding would help to predict preoperatively the organ confined versus non-organ confined growth of prostate cancer. MATERIALS AND METHODS A total of 68 consecutive men underwent radical retropubic prostatectomy for clinically localized prostate cancer. Serum was obtained 1 day preoperatively before prostatic manipulation. hK2, and total and free prostate specific antigen (PSA) were measured using immunofluorometric assays. Mean, median and range of hK2, total and free PSA, and the ratio of free-to-total PSA (percent free PSA) were calculated. Each analyte or combination of analytes was evaluated to determine whether it significantly contributed to enhance the discrimination of organ confined from non-organ confined cancer. We calculated the statistical significance of observed differences using the Mann-Whitney U and Kruskal-Wallis tests. Sensitivity and specificity calculations were performed for hK2, total PSA and the algorithm, (hK2) x (total PSA/free PSA) in addition to receiver operating characteristics curves and the respective areas under the curves. Multivariate logistic regression analysis was done for hK2, and total and free PSA RESULTS: Disease was organ and non-organ (extraprostatic extension) confined in 38 and 30 men, respectively. In organ confined cancer mean hK2 was significantly lower than in non-organ confined cancer (0.09 ng./ml., range less than 0.03 to 0.23 versus 0.30, range 0.04 to 0.94, p <0.0001). In addition, there was significantly higher free and total but not percent free PSA in non-organ than in organ confined cases. There were also statistically significant differences in hK2, free PSA and total PSA at each pathological disease stage (p <0.001, <0.01 and <0.05, respectively). Sensitivity for detecting organ confined disease was 37% at 100% specificity (correct identification of all non-organ confined cancer) using hK2 measurements compared with a sensitivity of 14% for total PSA. At a specificity of 95%, sensitivity was 40% for hK2 versus 23% for total PSA, which was a statistically significant gain in sensitivity (p <0.05). Receiver operating characteristics curves demonstrated that hK2 had the largest area under the curve, followed by the algorithm, (hK2) x (total PSA/free PSA), and total PSA (0.76, 0.75 and 0.72, respectively). However, none of area under the curve differences was statistically significant. CONCLUSIONS Compared with total and free PSA hK2 testing improved the preoperative evaluation of patients who underwent radical retropubic prostatectomy due to the superior discrimination of organ from non-organ confined cancer.

Clinical value of human glandular kallikrein 2 and free and total prostate-specific antigen in serum from a population of men with prostate-specific antigen levels 3.0 ng/mL or greater.

OBJECTIVES To investigate the clinical value of human glandular kallikrein 2 (hK2) compared with free (f) and total (t) prostate-specific antigen (PSA) in the early detection of prostate cancer (PCa). METHODS In PCa screening conducted in 1995 to 1996 in Göteborg, Sweden, 5853 of 9811 randomly selected men (aged 50 to 66 years; median 61) accepted PSA testing; those with tPSA levels of 3. 0 ng/mL or greater were offered digital rectal examination, transrectal ultrasound, and sextant biopsies. Serum from 604 of 611 biopsied men (18% with positive digital rectal examinations, tPSA range 3.0 to 220 ng/mL, 144 men with PCa) was analyzed for hK2 (research assay) and tPSA and fPSA (Prostatus). Sera were stored at -20 degrees C for a maximum of 2 weeks for tPSA and fPSA and 3 years for hK2. RESULTS hK2 levels and hK2 x tPSA/fPSA values were significantly elevated in men with PCa. Receiver operating characteristic data revealed that the area under the curve for hK2 x tPSA/fPSA was significantly greater than that for tPSA and greater, but not significantly greater, than that for percent fPSA. Also, the cancer-detecting sensitivity was significantly improved (P <0.05) using hK2 x tPSA/fPSA compared with tPSA and percent fPSA at specificity levels of 75% to 90%. At 75% specificity, a sensitivity of 74% was obtained compared with 64% or 54% using percent fPSA or tPSA; at 90% specificity, the corresponding sensitivity level was 55%, 41%, and 36%, respectively. CONCLUSIONS Discrimination of men with and without PCa in a randomly selected population was improved by measuring hK2 in addition to tPSA and fPSA.

Would prostate cancer detected by screening with prostate-specific antigen develop into clinical cancer if left undiagnosed? A comparison of two population-based studies in Sweden.

Objective To assess the risk of over‐diagnosing and over‐treating prostate cancer if population‐based screening with serum prostate‐specific antigen (PSA) is instituted.

Risk assessment for biochemical recurrence prior to radical prostatectomy: significant enhancement contributed by human glandular kallikrein 2 (hk2) and free prostate specific antigen (PSA) in men with moderate PSA-elevation in serum

Most models to predict biochemical recurrence (BCR) of prostate cancer use pretreatment serum prostate‐specific antigen (PSA), clinical stage and prostate biopsy Gleason grade. We investigated whether human glandular kallikrein 2 (hK2) and free prostate‐specific antigen (fPSA) measured in pretreatment serum enhance prediction. We retrospectively measured total PSA (tPSA), fPSA and hK2 in preoperative serum samples from 461 men with localized prostate cancer treated with radical prostatectomy between 1999 and 2001. We developed a regression model to predict BCR using preoperative tPSA, clinical stage and biopsy Gleason grade. We then compared the predictive accuracy of this “base” model with a model with fPSA and hK2 as additional predictors. BCR was observed in 90 patients (20%), including 48 patients with a pretreatment tPSA ≤ 14 ng/ml (13%), and 28 patients (10%) with a pretreatment tPSA ≤ 10 ng/ml. Overall, the predictive accuracy of the base model (bootstrap‐corrected concordance index of 0.813) was not improved after the addition of fPSA or hK2 (0.818). However, for men with moderate tPSA‐elevation (tPSA ≤ 10 ng/ml), addition of fPSA and hK2 data increased predictive accuracy (from a base model concordance index of 0.756–0.815, p = 0.005). The improvement in accuracy was not sensitive to the threshold for “moderately elevated” PSA. For patients with a moderate tPSA‐elevation (tPSA ≤ 10 ng/ml), which closely corresponds to concurrent disease demographics, BCR‐prediction was enhanced when fPSA and hK2 were added to the conventional model. Measurements of fPSA and hK2 improve on our ability to counsel patients prior to treatment as to their risk of BCR.

Toward Next Generation Plasma Profiling via Heat-induced Epitope Retrieval and Array-based Assays

There is a need for high throughput methods for screening patient samples in the quest for potential biomarkers for diagnostics and patient care. Here, we used a combination of undirected target selection, antibody suspension bead arrays, and heat-induced epitope retrieval to allow for protein profiling of human plasma in a novel and systematic manner. Several antibodies were found to reveal altered protein profiles upon epitope retrieval at elevated temperatures with limits of detection improving into lower ng/ml ranges. In a study based on prostate cancer patients, several proteins with differential profiles were discovered and subsequently validated in an independent cohort. For one of the potential biomarkers, the human carnosine dipeptidase 1 protein (CNDP1), the differences were determined to be related to the glycosylation status of the targeted protein. The study shows a path of pursuit for large scale screening of biobank repositories in a flexible and proteome-wide fashion by utilizing heat-induced epitope retrieval and using an antibody suspension bead array format.