Longitudinal assessment of urinary PCA3 for predicting prostate cancer grade reclassification in favorable-risk men during active surveillance.

BACKGROUND: To assess the utility of urinary prostate cancer antigen 3 (PCA3) as both a one-time and longitudinal measure in men on active surveillance (AS). METHODS: The Johns Hopkins AS program monitors men with favorable-risk prostate cancer with serial PSA, digital rectal examination (DRE), prostate magnetic resonance imaging and prostate biopsy. Since 2007, post-DRE urinary specimens have also been routinely obtained. Men with multiple PCA3 measures obtained over ⩾3 years of monitoring were included. Utility of first PCA3 score (fPCA3), subsequent PCA3 (sPCA3) and change in PCA3 were assessed for prediction of Gleason grade reclassification (GR, Gleason score >6) during follow-up. RESULTS: In total, 260 men met study criteria. Median time from enrollment to fPCA3 was 2 years (interquartile range (IQR) 1-3) and from fPCA3 to sPCA3 was 5 years (IQR 4-6). During median follow-up of 6 years (IQR 5-8), 28 men (11%) underwent GR. Men with GR had higher median fPCA3 (48.0 vs 24.5, P=0.007) and sPCA3 (63.5 vs 36.0, P=0.002) than those without GR, while longitudinal change in PCA3 did not differ by GR status (log-normalized rate 0.07 vs 0.06, P=0.53). In a multivariable model including age, risk classification and PSA density, fPCA3 remained significantly associated with GR (log(fPCA3) odds ratio=1.77, P=0.04). CONCLUSIONS: PCA3 scores obtained during AS were higher in men who underwent GR, but the rate of change in PCA3 over time did not differ by GR status. PCA3 was a significant predictor of GR in a multivariable model including conventional risk factors, suggesting that PCA3 provides incremental prognostic information in the AS setting.

Use of the Prostate Health Index for detection of prostate cancer: results from a large academic practice.

BACKGROUND: The Prostate Health Index (phi) outperforms PSA and other PSA derivatives for the diagnosis of prostate cancer (PCa). The impact of phi testing in the real-world clinical setting has not been previously assessed. METHODS: In a single, large, academic center, phi was tested in 345 patients presenting for diagnostic evaluation for PCa. Findings on prostate biopsy (including Grade Group (GG), defined as GG1: Gleason score (GS) 6, GG2: GS 3+4=7, GG3: GS 4+3=7, GG4: GS 8 and GG5: GS 9-10), magnetic resonance imaging (MRI) and radical prostatectomy (RP) were prospectively recorded. Biopsy rates and outcomes were compared with a contemporary cohort that did not undergo phi testing (n=1318). RESULTS: Overall, 39% of men with phi testing underwent prostate biopsy. No men with phi<19.6 were diagnosed with PCa, and only three men with phi<27 had cancer of GG⩾2. Phi was superior to PSA for the prediction of any PCa (area under the receiver operating characteristic curve (AUC) 0.72 vs 0.47) and GG⩾2 PCa (AUC 0.77 vs 0.53) on prostate biopsy. Among men undergoing MRI and phi, no men with phi<27 and PI-RADS⩽3 had GG⩾2 cancer. For those men proceeding to RP, increasing phi was associated with higher pathologic GG (P=0.002) and stage (P=0.001). Compared with patients who did not undergo phi testing, the use of phi was associated with a 9% reduction in the rate of prostate biopsy (39% vs 48%; P<0.001). Importantly, the reduction in biopsy among the phi population was secondary to decreased incidence of negative (8%) and GG1 (1%) biopsies, whereas the proportion of biopsies detecting GG⩾2 cancers remained unchanged. CONCLUSIONS: In this large, real-time clinical experience, phi outperformed PSA alone, was associated with high-grade PCa, and provided complementary information to MRI. Incorporation of phi into clinical practice reduced the rate of unnecessary biopsies without changing the frequency of detection of higher-grade cancers.

Prostate involvement during sexually transmitted infections as measured by prostate-specific antigen concentration.

BACKGROUND: We investigated prostate involvement during sexually transmitted infections by measuring serum prostate-specific antigen (PSA) as a marker of prostate infection, inflammation, and/or cell damage in young, male US military members. METHODS: We measured PSA before and during infection for 299 chlamydia, 112 gonorrhoea, and 59 non-chlamydial, non-gonococcal urethritis (NCNGU) cases, and 256 controls. RESULTS: Chlamydia and gonorrhoea, but not NCNGU, cases were more likely to have a large rise (40%) in PSA than controls (33.6%, 19.1%, and 8.2% vs 8.8%, P<0.0001, 0.021, and 0.92, respectively). CONCLUSION: Chlamydia and gonorrhoea may infect the prostate of some infected men.

Plasma selenium level before diagnosis and the risk of prostate cancer development.

PURPOSE: Epidemiological studies and a randomized intervention trial suggest that the risk of prostate cancer may be reduced by selenium intake. We investigated whether plasma selenium level before diagnosis correlated with the risk of later developing prostate cancer. MATERIALS AND METHODS: A case control study was performed on men from the Baltimore Longitudinal Study of Aging registry, including 52 with known prostate cancer and 96 age matched controls with no detectable prostatic disease. Plasma selenium was measured at an average time plus or minus standard deviation of 3.83 +/- 1.85 years before the diagnosis of prostate cancer by graphite furnace atomic absorption spectrophotometry. Adjusted odds ratio and 95% confidence interval were computed with logistic regression. RESULTS: After correcting for years before diagnosis, body mass index, and smoking and alcohol use history, higher selenium was associated with a lower risk of prostate cancer. Compared with the lowest quartile of selenium (range 8.2 to 10.7 microg./dl.), the odds ratios of the second (10.8 to 11.8), third (11.9 to 13.2) and fourth (13.3 to 18.2) quartiles were 0.15 (95% confidence interval 0.05 to 0.50), 0.21 (0.07 to 0.68) and 0.24 (0.08 to 0.77, respectively, p =0.01). Furthermore, plasma selenium decreased significantly with patient age (p <0.001). CONCLUSIONS: Low plasma selenium is associated with a 4 to 5-fold increased risk of prostate cancer. These results support the hypothesis that supplemental selenium may reduce the risk of prostate cancer. Because plasma selenium decreases with patient age, supplementation may be particularly beneficial to older men.

Immunosensors--principles and applications to clinical chemistry.

INTRODUCTION: Immunosensors are affinity ligand-based biosensor solid-state devices in which the immunochemical reaction is coupled to a transducer. The fundamental basis of all immunosensors is the specificity of the molecular recognition of antigens by antibodies to form a stable complex. This is similar to the immunoassay methodology. Immunosensors can be categorized based on the detection principle applied. The main developments are electrochemical, optical, and microgravimetric immunosensors. In contrast to immunoassay, modern transducer technology enables the label-free detection and quantification of the immune complex. METHODS: The analysis of trace substances in environmental science, pharmaceutical and food industries is a challenge since many of these applications demand a continuous monitoring mode. The use of immunosensors in these applications is most appropriate. Similarly, a series of clinical problems may be solved by continuous monitoring of certain analytes. CONCLUSIONS: Clinical chemists should take advantage of immunosensors in clinical diagnostics. There are many recent developments in the immunosensor field which have potential impacts. The future role of this technique in intralaboratory, as well as bedside testing, will become even more important as the clinical laboratory is faced with increasing pressure to contain costs.

Concentration of enzymatically active prostate-specific antigen (PSA) in the extracellular fluid of primary human prostate cancers and human prostate cancer xenograft models.

BACKGROUND: Prostate-specific antigen (PSA) targeted prodrugs are under development in our laboratory. Concentrations of total PSA and enzymatically active PSA produced by various human prostate cancer xenograft models have not been well characterized. METHODS: The concentration of PSA secreted into the extracellular fluid (ECF) in normal human prostate tissue, primary prostate cancers obtained directly from patients, and serially passageable human prostate cancer xenografts (PC-82, LNCaP, LAPC-4) were determined using Tandem assays. Percent enzymatically active PSA in the ECF and in conditioned media was also determined using a previously validated assay employing a monoclonal antibody to the PSA catalytic site. In addition, the concentration and activity of PSA within sera from men with and without prostate cancer, as well as from tumor-bearing animals, was likewise assayed. RESULTS: Normal human prostate tissue and primary human prostate cancers have high concentrations of PSA in the ECF (i.e., 1600-2100 nM). The majority of this PSA is enzymatically active (i.e., 80-90%). Human PC-82 prostate cancer xenografts also have high concentrations of PSA in the ECF (624 +/- 360 nM), and the majority of this PSA is also enzymatically active (i.e., 66 +/- 4%). In contrast, much lower concentrations of PSA are found in the ECF from LNCaP (45 +/- 9 nM) and LAPC-4 (7.3 +/- 0.6 nM). Only a small portion of the total PSA isolated from DHT-containing, serum-free, conditioned media from these cell lines is enzymatically active (i.e., approximately 18%). While PSA was detected in all serum samples regardless of the type of host, no enzymatically active PSA was detected in any of these serum samples. CONCLUSIONS: Prostate cancers obtained directly from patients produce and secrete large amounts of PSA, the majority of which is highly enzymatically active. In contrast, while PSA was detected in the sera, none of this PSA was enzymatically active. This is also the case for the human PC-82 prostate cancer xenografts. In contrast, LNCaP and LAPC-4 human prostate cancer xenograft models secrete approximately 70-300-fold less PSA in the ECF than prostate cancers from patients and the majority of this PSA is enzymatically inactive. Also, the serum from these animals had detectable PSA, but none of this PSA was enzymatically active. Thus, these latter two prostate cancer models define the least and the PC-82, the most, optimized xenograft model for screening PSA targeted prodrugs.

Serum acid phosphatase level and biochemical recurrence following radical prostatectomy for men with clinically localized prostate cancer.

OBJECTIVES: Serum acid phosphatase (ACP) was once used as the marker for advanced prostate cancer. However, with the development of assays for prostate-specific antigen (PSA), a more sensitive and specific tumor marker, the use of ACP has diminished. We investigated the prognostic value of preoperative serum ACP in predicting prognosis for men with localized prostate cancer following radical retropubic prostatectomy (RRP). METHODS: Of 2293 men treated from 1982 to 1998, 1681 men had a preoperative ACP measurement using an enzymatic assay. We analyzed the actuarial freedom from biochemical (PSA) progression following RRP according to ACP levels. We used multivariate logistic regression and proportional hazards models to determine the independent prognostic value of ACP level with respect of pathologic stage and biochemical recurrence. RESULTS: ACP was not an independent predictor of organ confinement or lymph node involvement in the multivariate logistic regression models using preoperative variables. However, in the proportional hazards model, ACP was an independent predictor of tumor recurrence following RRP, and there was a statistically significant improvement in biochemical recurrence-free survival for men with lower levels of ACP (P <0.001). Furthermore, the normalized hazard ratios of ACP and PSA for predicting biochemical recurrence were similar. CONCLUSIONS: Stratification of men according to their preoperative ACP levels was predictive of patient outcome after RRP. Proportional hazards modeling using preoperative variables demonstrated that the serum ACP level is an independent predictor of tumor recurrence following RRP.

Fatty acid synthase (FAS) expression in human breast cancer cell culture supernatants and in breast cancer patients.

Fatty acid synthase (FAS) is selectively expressed in certain human cancers, including carcinoma of the breast, prostate, colon, ovary, and endometrium, compared to normal human tissues and therefore is a putative tumor marker. In this study, we found FAS concentrations were elevated in cell culture supernatants during cell growth in two human breast cancer cell lines but not other cancer cell lines. A quantitative enzyme-linked immunosorbent assay and Western blot analysis were employed in this study. In addition, serum FAS levels were significantly higher in breast cancer patients with different clinical stages (Stage II: 0.59+/-0.09 units/l, Stage III: 0.79+/-0.13 units/l, and Stage IV: 1.39+/-0.35 units/l) compared with healthy subjects (0.27+/-0.02 units/l, P<0.05). Taken together, our data suggest that FAS expression may be a useful tumor marker for breast cancer and play a role in assessing cancer virulence.

Two-site ELISA for the quantitative determination of fatty acid synthase.

Fatty acid synthase (FAS) is an enzyme which plays a central role in the de novo biosynthesis of fatty acids. FAS is selectively expressed in certain human cancers and therefore is a putative tumor marker. We developed an enzyme-linked immunosorbent assay (ELISA) for measuring FAS, and investigated its expression and clinical features. In this two-site sandwich ELISA, a polyclonal antibody was used as a capture on Nunc MaxiSorp ELISA/EIA modules and a monoclonal antibody labeled with biotin was used as a signal antibody. The assay was linear with no cross-reactivity with other tumor markers. The within- and between-run CVs were <10%, and the detection limit was 0.15 arbitrary Units/l. Recoveries were 92.4-105.1%. FAS was stable in buffer at 4 degrees C for more than 10 days and stable at 37 degrees C for 2 days. In human serum, FAS levels were significantly higher in patients with breast (1.01+/-0.71 Units/l, mean+/-S.D.), prostate (0.79+/-0.76 Units/l), colon (0.89+/-0.49 Units/l), and ovarian (0.84+/-0.9 Units/l) cancers compared to normal subjects (0.27+/-0.09 Units/l, P<0.01). This assay is sensitive, accurate, and precise and can distinguish between patients with various types of cancer and normal subjects.

Redesigned proficiency testing materials improve survey outcomes for prostate-specific antigen. A College of American Pathologists Ligand Assay Survey tool.

CONTEXT: Large disparities in prostate-specific antigen (PSA) results from different assays have been observed in the College of American Pathologists (CAP) Ligand Assay Survey, with interassay results varying severalfold. Survey specimens are predominately composed of free PSA and do not reflect the composition of typical patient specimens. OBJECTIVES: To characterize a pilot material developed for CAP in which pooled sera samples were spiked with purified PSA and alpha(1)-antichymotrypsin-bound PSA at targeted concentrations and to compare it to CAP survey and reference materials. DESIGN: CAP survey, reference, and pilot materials were analyzed using 10 total PSA and 7 free PSA assays. These assays included Food and Drug Administration-approved assays and assays for research use only. RESULTS: Variability among the 10 total PSA methods was greatest for the 1997 ligand survey material (CV range, 56%-65%) followed by the pilot material (CV range, 10%-29%) and the reference material (CV range, 6%-13%). In contrast, interassay variability for the 7 free PSA methods was similar for the 3 preparations, with the exception of one specimen close to the limit of detection of the assays. As determined with the Hybritech Tandem-R method, the ligand survey specimens were essentially composed of all free PSA, whereas the reference and pilot materials were composed of approximately 10% and 35% free PSA, respectively. CONCLUSIONS: The newly formulated pilot material prepared using a human base that contained defined concentrations of free PSA and alpha(1)-antichymotrypsin-bound PSA more closely resembled patient specimens and minimized differences among methods compared with the semen-supplemented original survey material.

Intraoperative parathyroid hormone analysis: A study of 200 consecutive cases.

BACKGROUND: Immunoassays for parathyroid hormone (PTH), with short incubation times and results available in <15 min, have allowed intraoperative monitoring of the success of parathyroid surgery. The purpose of this study was to evaluate the analytical performance of a rapid PTH assay and its clinical performance in a series of 200 patients. METHODS: PTH was measured with a modified immunochemiluminometric assay with a 7-min incubation time (QuiCk-IntraOperative(TM) Intact PTH assay). The rapid assay was compared with results in a central laboratory (immunoradiometric assay) in 44 EDTA-plasma specimens. The rapid assay was used intraoperatively in 200 consecutive cases with specimens analyzed before and 5-10 min after resection of the hypersecreting parathyroid gland(s). RESULTS: Intraassay imprecision was 12% at 28 ng/L and 11% at 278 ng/L. Regression analysis of results of the rapid PTH assay and the IRMA PTH assay in 44 parathyroidectomy patients yielded y = 1.26x - 12 ng/L, S:(y|x) = 26.3 ng/L, r = 0.984, and in 40 of 44 patients with values <200 ng/L, y = 1.02x + 1.9, S:(y|x) = 13.9, r = 0.947. In the 195 cases using intraoperative PTH testing with complete results and defined clinical outcomes, the overall accuracy of the assay in predicting surgical success was 88% using the criterion of a 50% decrease at 5-10 min and 97% including the subset of patients with delayed decreases of PTH. CONCLUSIONS: The rapid PTH assay had excellent analytical performance and excellent agreement with the PTH immunoradiometric assay and predicted the success of parathyroid surgery in this large series of consecutive patients.

One hundred consecutive minimally invasive parathyroid explorations.

OBJECTIVE: To review the outcomes of 100 consecutive minimally invasive parathyroid explorations. SUMMARY BACKGROUND DATA: Minimally invasive parathyroidectomy (MIP) has challenged the traditional approach of bilateral neck exploration for patients with primary hyperparathyroidism. Most patients with primary hyperparathyroidism have a single adenoma that when resected results in cure. It therefore appears logical to perform a directed approach to adenoma extirpation. MIP involves high-quality sestamibi images obtained with single photon emission computed tomography to localize enlarged parathyroid glands in three dimensions, limited exploration after surgeon-administered cervical block anesthesia, rapid intraoperative parathyroid hormone assay to confirm the adequacy of resection, and discharge within 1 to 3 hours of surgery. METHODS: MIP was offered to 100 selected consecutive patients during an 18-month period beginning in March 1998. RESULTS: Ninety-two cases were accomplished under cervical block anesthesia and 89 of these on an ambulatory basis. The cure rate was 100%, and there were no long-term complications. The mean hospital charge for MIP was less than 40% of that associated with traditional exploration. CONCLUSIONS: Outpatient MIP appears to be the procedure of choice for most patients with primary hyperparathyroidism.

Multiple site analytical evaluation of a portable blood gas/electrolyte analyzer for point of care testing.

OBJECTIVE: To evaluate the analytical performance of the SenDx 100 portable blood gas and electrolyte analyzer (SenDx Medical, Carlsbad, CA). DESIGN: Accuracy was evaluated by correlation of whole blood patient samples with the Nova Stat Profile 5 (Nova Biomedical, Waltham, MA) and the Ciba Corning 865 (Chiron Diagnostics, Medford, MA). Precision was evaluated using quality control materials (RNA Medical, Acton, MA). SETTING: Critical care laboratories and operating rooms in two institutions. MEASUREMENTS AND MAIN RESULTS: Precision studies performed at three different concentration levels for each analyte demonstrated intra-assay precision of < or =2.5% coefficient of variation and interassay precision of < or =4.0% coefficient of variation in all cases. Analysis of patient specimens in general showed good to excellent correlation to reference analyzers. Regression variables are tabulated. CONCLUSIONS: The SenDx 100 portable blood gas and electrolyte analyzer is a simple and easy to use analyzer demonstrating acceptable performance compared with reference methods.

Probability of prostate cancer detection based on results of a multicenter study using the AxSYM free PSA and total PSA assays.

OBJECTIVES: The determination of the percentage of free prostate-specific antigen (%fPSA) enhances the specificity of prostate cancer (CaP) detection. This study was undertaken to assess the performance of %fPSA in differentiating benign prostate disease from CaP and to determine the CaP probability estimates using the AxSYM Free PSA and AxSYM Total PSA assays. METHODS: In this prospective study, 297 men, 50 years old or older, with a total PSA level between 4 and 10 ng/mL and a nonsuspicious digital rectal examination were enrolled at 10 clinical sites. All subjects underwent at least sextant prostate biopsies to establish the diagnosis. fPSA and total PSA (tPSA) levels were determined using the AxSYM Free PSA and AxSYM Total PSA assays. Percent fPSA values were compared with tPSA values to determine the appropriate cutoffs for prostate biopsy and to calculate the CaP probability estimates. RESULTS: The strongest predictor of CaP in a logistic regression model was %fPSA (odds ratio 2.29), which contributed significantly more than age or tPSA to the predictive model. In this study population, a %fPSA cutoff of 26.4% would have detected 96% of subjects with CaP (sensitivity) and would have eliminated 27.4% of unnecessary biopsies (specificity). CaP probability estimates ranged from 9% to 69% and increased as the %fPSA value decreased. Men with a %fPSA level of 10% or lower had a 69% probability of CaP, and men with a %fPSA level of greater than 26% had a 9% probability of CaP. CONCLUSIONS: Percent fPSA values can help differentiate CaP from benign prostate disease and reduce unnecessary biopsies in 27% of men 50 years old or older whose digital rectal examination was normal and whose tPSA level was between 4 and 10 ng/mL. A %fPSA result can assist the physician and patient in determining the probability of CaP and assessing the need for prostate biopsy.

Rapid parathyroid hormone measurement during venous localization.

The development of a rapid format for intact parathyroid hormone (PTH) immunometric assays has facilitated the use of these assays intraoperatively as a guide to parathyroid surgery. The near real-time characteristics of this rapid PTH assay led us to evaluate its utility in the angiography suite in a patient who underwent venous localization for persistent primary hyperparathyroidism. The assay provided the angiographers with almost immediate feedback and thereby facilitated accurate parathyroid adenoma localization. We conclude that the performance characteristics of the rapid PTH assay extend its diagnostic utility to near real-time analysis of plasma PTH levels in patients undergoing venous catheterization for parathyroid localization.

Complexed prostate specific antigen provides significant enhancement of specificity compared with total prostate specific antigen for detecting prostate cancer.

PURPOSE: Determining serum total prostate specific antigen (PSA) has proved to be a valuable diagnostic aid for detecting prostatic carcinoma, although the lack of specificity has limited its usefulness. Studies indicate that the use of percent free PSA would improve specificity while maintaining sensitivity. Since complexed PSA represents the major proportion of measurable PSA in serum, we determined whether it represents a single test alternative to the use of percent free PSA for the early detection of prostate cancer. MATERIALS AND METHODS: Archival serum was obtained from 385 men with no evidence of malignancy on biopsy and 272 with biopsy confirmed prostate cancer. We determined the concentration and proportion of total, complexed and free PSA. RESULTS: Receiver operating characteristics analysis using total PSA results from all samples (range 0.32 to 117 ng./ml.) indicated that the areas under the curve for complexed PSA alone as well as the free-to-total and complexed-to-total PSA ratios were similar and significantly greater than those for total PSA alone. Within the range of 85% to 95% sensitivity receiver operating characteristics analysis revealed that the specificity of complexed PSA was higher than that of total PSA and equivalent to that of the free-to-total PSA ratio. We noted a similar improvement in specificity in the 4 to 10 ng./ml. total PSA range. Using published cutoff values for complexed, total and percent free PSA when total PSA was in the 4 to 10 ng./ml. range the sensitivity and specificity of complexed and percent free PSA were similar. Within the 4 to 10 ng./ml. total PSA range the population of patients with no evidence of malignancy and complexed PSA below the upper limit was different with respect to total PSA from that with no evidence of malignancy and free PSA greater than 25%. CONCLUSIONS: The measurement of complexed PSA represents an alternative to the use of percent free PSA, although the patient populations identified by the 2 tests are different.