Prostate-specific antigen and prostate gland volume: correlation and clinical application

Prostate-specific antigen screening for prostate cancer: Diagnostic performance, clinical thresholds, and strategies for refinement

Prostate specific antigen (PSA) has transformed the diagnosis and treatment of prostate cancer by enabling early detection at global scale. Due to expression in both benign and malignant cells, PSA-based prostate cancer screening using single cut-points yields imperfect diagnostic performance and has led to the detection and over-treatment of low-grade prostate cancer. Additional challenges in the interpretation of PSA include substantial inter and intrapersonal variation, differences with age and prostate volume, and selection of standardized PSA value cutoffs for clinical application. In response, refinements to PSA including risk and age-based thresholds, age and genetic adjustments, PSA density, percentage free PSA, and PSA velocity have been proposed and extensively studied. In this review, we focus on the clinical role of PSA as a screening biomarker with a particular emphasis on its test characteristics, clinically actionable thresholds, and strategies to refine its clinical interpretation.

PSA change after antibiotic treatment should not affect decisionmaking on performing a prostate biopsy

BACKGROUND

To investigate the effect of antibiotic treatment on PSA when deciding on prostate biopsy.

METHODS

A total of 206 patients with an elevated PSA level (2.5-30) were included. Mp-MRI could be done on 129 patients. Patients were given ciprofloxacin (500 mg, b.i.d. p.o.) for 4 weeks and PSA measurements were repeated. Systematic prostate biopsy was performed regardless of PSA changes on all patients. Additionally, cognitive biopsies were performed from PI-RADs III, IV, and V lesions.

RESULTS

: Prostate cancer was detected in 36.4% of patients. 53.3% had Gleason score of 3+3, 46.7% had Gleason score ≥ 3+4. PSA values decreased in 56.3% and in 43.7% and remained the same or increased but cancer detection rates were not different: 34.5% vs. 38.9%, respectively (p = 0.514). PSA change in whole group was significant (6.38 ng/mL vs. 5.95 ng/mL, respectively (p = 0.01). No significant PSA decrease was observed in cancer patients (7.1 ng/mL vs. 7.05 ng/mL, p = 0.09), whereas PSA decrease was significant in patients with benign pathology (6.1 ng/mL vs. 5.5 ng/mL, p = 0.01). In patients with PI-RADs IV-V lesions, adenocarcinoma was present in 33.9% and 30.4% with or without PSA decrease, respectively (p = 0.209). Clinically significant cancer was higher in patients with after antibiotherapy PSA values >4 ng/mL regardless of PI-RADs grouping (p = 0.08). Addition of any PSA value to PI-RADs grouping did not have any significant effect on the detection of cancer.

DISCUSSION

PSA change after antibiotic treatment has no effect in detecting cancer and should not delay performing a biopsy.

Predictive value of PSA density in the diagnosis of prostate cancer in lebanese men

OBJECTIVE

Being the second most common cancer in men, prostate cancer detection relies on laboratory tests, imaging, and surgical procedures, although biopsy remains the mainstay in diagnosis of prostate cancer. No clear cut-off of prostate specific antigen density (PSAD) for suspecting prostate cancer has been established in the Lebanese population. Our primary objective was to evaluate the diagnostic strength of the PSAD value versus total prostate specific antigen (tPSA) level in the Lebanese men in correlation with biopsy outcome to avoid unnecessary prostate biopsy.

METHODS

A retrospective study of 347 patients with history of prostate biopsy done for cancer suspicion included tPSA, prostate volume, and prostate density values and results of prostate biopsy. Data was collected from Bahman hospital and statistical analysis of the mean values of tPSA, prostate volume and PSAD in different age groups was done. Significance of the results was tested using.

RESULTS

On average, patients with negative biopsies were younger and they had lower tPSA levels, lower PSAD values and larger prostate volume compared to patients with positive biopsies. A PSAD cutoff of 0.185 ng/ml2 revealed the highest predictive strength for prostate cancer (6 times risk) compared with other parameters. These findings were mainly referred to patients with PSA > 10 ng/ml.

CONCLUSIONS

A multifactorial approach must be conducted including all parameters in order to decide upon the need for prostate biopsy. PSAD proved to be a good marker in favor or against a prostate biopsy with a cut-off of 0.185 ng/ml2, especially in patients with tPSA level higher to 10 ng/ml. A multicenter study was recommended for better and more reliable results and more precise cut-offs.

The prostate health index (PHI) density: Are there advantages over PHI or over the prostate-specific antigen density?

BACKGROUND AND AIMS

Overdiagnosis of prostate cancer (PCa) should be minimized. We wanted to evaluate the diagnostic performance of the prostate health index density (PHID) and compare it with that of the prostate health index (PHI) alone and of the prostate-specific antigen density (PSAD).

MATERIALS AND METHODS

232 men scheduled for a prostate biopsy (prostate-specific antigen level: 2-10 µg/L), were enrolled. PHI, PHID and PSAD were evaluated considering PCa and clinically significant PCa (csPCa) as the outcomes.

RESULTS

For PCa, the area under the curve (AUC) was higher for PHID (0.823) than for PHI (0.779) and PSAD (0.776). For csPCa, the AUC was also higher for PHID (0.851) but closer to that of PSAD (0.819) and PHI (0.813). For equal sensitivities (90%) for PCa, PHID and PSAD offered the highest specificities (37%), missing the same number of cancers (n = 11). Considering csPCa, PHI and PHID had similar specificities. PSAD reached the highest specificity (50.0%), sparing 32.8% of biopsies, while missing 9 cases of csPCa.

CONCLUSIONS

PHID has a better diagnostic performance than PHI for overall PCa detection, but very close to the PSAD performance. Considering csPCa, PHI and PHID perform almost equally, but PSAD has a better diagnostic performance.

Relationship between serum prostate-specific antigen and transrectal prostate sonographic findings in asymptomatic Ugandan males

Background

Prostate disorders are among the leading causes of morbidity and mortality in men above the age of 40 years globally. Serum prostate-specific antigen (PSA) levels may be used to screen men at risk of prostate cancer and determine choice of medical treatment in benign prostatic hyperplasia (BPH) and evaluation of patients with prostatitis, while prostate sonography determines prostate volume (PV) and detects nodules. BPH may exhibit distinct hypoechoic, isoechoic, or hyperechoic nodules in the transition zone, whereas hypoechoic nodules in the peripheral zone are diagnostic for prostate cancer in over 50% of cases. In this study, we aimed at determining the relationship between serum PSA levels and transrectal prostate sonographic findings among asymptomatic Ugandan males.

Methods

Ugandan males above 30 years of age or older without lower urinary tract symptoms were cross-sectionally enrolled into the study. Serum PSA determination and transrectal ultrasound were performed. Association between PSA levels and PV was assessed using Spearman’s correlation coefficients (ρ).

Results

A total of 277 men were studied. The median serum PSA level was 1 (95% CI: 1–2). Most (n = 217, 78.3%) participants had serum PSA levels ≤ 4 ng/ml. The median sonographic PV was 26 (95% CI: 26–29) mls. One hundred and fifty-five (56.0%) participants had PV between 25 and 50 mls. Both PSA levels and PV progressively increased with age from 0.9 ng/ml and 22 mls in the 30–39 year age group to 7 ng/ml and 38 mls in the 60–69 year age group, respectively. PSA levels weakly correlated with PV (ρ = 0.27) (p < 0.0001). One hundred and thirty (47%) participants had prostatic nodules. Of these, 100 (77%) had features of benign nodules and 23% had suspicious nodules for prostate cancer. The median (range) serum PSA level in those with nodules was 2.0 (0.1–16.0) ng/ml and for those without nodules was 1.1 (0.1–8.0) ng/ml (p < 0.0001).

Conclusions

Serum PSA has a weak direct correlation with PV and not a reliable marker for the prediction of presence or absence of prostatic nodules in asymptomatic adult males.

[Prostate biopsy. Update for indication, procedure, and future developments]

Transrectal ultrasound-guided prostate biopsy is considered the gold standard in the primary investigation of a suspicious prostate-related finding. The procedure can be carried out with ten probes or more on the lateral side of the prostate, after administering antibiotic prophylaxis and applying local anesthesia. The indication for a biopsy depends on the results of the digitorectal examination, on the serum prostate-specific antigen level, on the individual patient's wish and on his comorbidities. Whether multiparametric imaging should be used before or during the course of a primary or repeated biopsy in order to identify suspicious prostate lesions is the subject of current investigations. Extended biopsy protocols require further clinical investigations before they can become the new standard in the diagnostic work-up. This review delivers an update on the indication for, and technique of, prostate biopsies.

Why I cannot find the prostate? Behind the subjectivity of rectal exam

Background. Most physicians use digital rectal examination (DRE) to help detect prostate cancer and to estimate the prostates' size. The accuracy of DRE is known to be limited. We evaluate the ability of doctors to palpate the whole prostate with DRE. Methods. At time of transrectal ultrasound (TRUS) the distances from the anus to the apex and base of prostates were measured. The TRUS's distances were compared to the mean index finger length of our clinic doctors. Results. The ability of the urologist to reach and examine the apex, half, three quarters and the whole prostate was in 93.7%, 66.3%, 23.2% and 3.2% of cases respectively. Conclusions. In most cases it was impossible to palpate the whole prostate. Anatomical location and volume of the examined prostate, as well as the length of his own index finger limit DRE and allow the examination of only a small portion of the prostate.

Contribuição da densidade do PSA para predizer o câncer da próstata em pacientes com valores de PSA entre 2,6 e 10,0 ng/ml

OBJETIVO: Estudar o perfil dos pacientes submetidos a biópsia prostática, determinando possíveis padrões que, associados aos níveis de PSA entre 2,6 e 10,0 ng/ml, possam levar a uma diminuição de biópsias desnecessárias. MATERIAIS E MÉTODOS: De 2007 a 2009, foi realizado um estudo transversal com 1.282 indivíduos submetidos a biópsia prostática e que apresentavam níveis de PSA entre 2,6 e 10,0 ng/ml. RESULTADOS: A prevalência de câncer foi de 28,6%. Pacientes com câncer eram, em média, mais idosos, com valores de PSA e densidade de PSA mais altos e menor volume da próstata. Na análise da densidade de PSA, os pacientes com câncer tiveram média de 0,31 ng/ml/cc, enquanto nos pacientes com resultado negativo a média foi de 0,10 ng/ml/cc. Utilizando como critério de positividade para câncer o ponto de corte de densidade de PSA de 0,15 ng/ml/cc, obtivemos especificidade de 74% e sensibilidade de 70%. Para aumentar a sensibilidade é preciso reduzir o ponto de corte. Com o valor 0,09 ng/ml/cc, obtivemos sensibilidade de 84% (IC 95%: 80-87%) e especificidade de 75% (IC 95%: 72-78%). CONCLUSÃO: O uso sistemático da densidade de PSA na indicação de prosseguimento da investigação do paciente com biópsia poderia reduzir a quantidade de procedimentos desnecessários.

Prostate kallikrein markers in diagnosis, risk stratification and prognosis

The kallikrein, prostate-specific antigen (PSA), is one of the world's most frequently used disease biomarkers. After almost two decades of research and clinical experience, the diagnostic and monitoring limitations of PSA are beginning to be understood. Most physicians are aware of PSA's low specificity for cancer among older men with benign prostatic conditions; fewer are aware of recent data, which show that a prior negative biopsy or a prior PSA value below the threshold for biopsy might compromise the predictive accuracy of PSA even further. Furthermore, a subtle increase in serum PSA level during early middle age is strongly correlated with clinically important prostate cancer. We review current and past reports on the prostate kallikreins PSA and hK2 in relation to pathology and epidemiology.

National Academy of Clinical Biochemistry Laboratory Medicine Practice Guidelines for Use of Tumor Markers in Testicular, Prostate, Colorectal, Breast, and Ovarian Cancers

Background: Updated National Academy of Clinical Biochemistry (NACB) Laboratory Medicine Practice Guidelines for the use of tumor markers in the clinic have been developed.

Methods: Published reports relevant to use of tumor markers for 5 cancer sites—testicular, prostate, colorectal, breast, and ovarian—were critically reviewed.

Results: For testicular cancer, α-fetoprotein, human chorionic gonadotropin, and lactate dehydrogenase are recommended for diagnosis/case finding, staging, prognosis determination, recurrence detection, and therapy monitoring. α-Fetoprotein is also recommended for differential diagnosis of nonseminomatous and seminomatous germ cell tumors. Prostate-specific antigen (PSA) is not recommended for prostate cancer screening, but may be used for detecting disease recurrence and monitoring therapy. Free PSA measurement data are useful for distinguishing malignant from benign prostatic disease when total PSA is &lt;10 μg/L. In colorectal cancer, carcinoembryonic antigen is recommended (with some caveats) for prognosis determination, postoperative surveillance, and therapy monitoring in advanced disease. Fecal occult blood testing may be used for screening asymptomatic adults 50 years or older. For breast cancer, estrogen and progesterone receptors are mandatory for predicting response to hormone therapy, human epidermal growth factor receptor-2 measurement is mandatory for predicting response to trastuzumab, and urokinase plasminogen activator/plasminogen activator inhibitor 1 may be used for determining prognosis in lymph node–negative patients. CA15-3/BR27–29 or carcinoembryonic antigen may be used for therapy monitoring in advanced disease. CA125 is recommended (with transvaginal ultrasound) for early detection of ovarian cancer in women at high risk for this disease. CA125 is also recommended for differential diagnosis of suspicious pelvic masses in postmenopausal women, as well as for detection of recurrence, monitoring of therapy, and determination of prognosis in women with ovarian cancer.

Conclusions: Implementation of these recommendations should encourage optimal use of tumor markers.

Structure-guided design of peptidic ligand for human prostate specific antigen

Prostate specific antigen (PSA) is a member of kallikrein family having serine protease-like activity and acts as a prognostic marker of prostate carcinoma. Various studies have been performed on inhibition of PSA and such targeting requires the identification of highly selective peptide inhibitors. PSA was purified from human seminal plasma by rapid and efficient methods, and binding studies for various peptides were carried out by fluorescence spectroscopy and SPR. The 'S' of PSA is predominated by hydrophobic residues, and hence many hydrophobic peptides were used to determine their binding affinity to PSA by fluorescence spectroscopy. We observed that LLFW, FFKW, and KFW binds strongly to PSA, among them LLFW showed strong binding. SPR also showed strong binding affinity of PSA toward peptides with hydrophobic and basic residues. Among the peptides used, FWYS showed dramatic increase in binding affinity (10(-10) M). The peptides analyzed for binding studies, suggests that peptide with Trp residue along with basic or hydrophobic amino acids may be useful for designing specific inhibitors for PSA. The strong affinities of designed peptides for PSA can be a valuable tool for designing therapeutic agents for prostate carcinomas.

Marqueurs biologiques du cancer de la prostate

Screening for prostate cancer is currently based on the assessment of blood prostate specific antigen (PSA). Although PSA was shown to be an adequate tool in prostate cancer screening, beginning from 4.0 ng/mL, its specificity is less significant. In men with a PSA between 4.0 and 10 ng/mL its predictive value is low. Therefore, there is a need for new instruments likely to improve the specificity of blood PSA levels between 4.0 and 10 ng/mL and the screening for prostate cancer in subjects with low PSA. Recent data are reviewed.

Population Standards of Prostate Specific Antigen Values in Men over 40: Community Based Study in Turkey

OBJECTIVE

To determine the prostate specific antigen (PSA) population standards of a cluster of Turkish men with no clinical evidence of prostate cancer.

PATIENTS AND METHODS

We evaluated PSA values of the men who were living in a well-defined, rural district of Western Anatolia. Two hundred fifty-seven men agreed to participate in this population-based study. They underwent clinical examination, transrectal ultrasonography and serum PSA measurement. The association between serum PSA and age, prostate volume and age, PSA and prostate volume, and PSA density (PSAD) and age were assessed. Distributions of serum PSA levels, prostate volumes (PV), and PSAD values as a function of age were generated.

RESULTS

The upper limit of normal PSA concentration were 4.51 ng/ml for men aged 40-49 years, 4.36 ng/ml for 50-59 years, 6.17 ng/ml for 60-69 years, and 10.18 ng/ml for over 70 years. The upper limit of normal (95th percentile) for the serum PSA concentration increased with age. Across the entire age range, no correlation was found between the serum PSA concentrations and age while significant correlation was found between serum PSA concentration and prostate volume.

CONCLUSION

In this present study, the PSA values in different age intervals showed higher than those observed in previous studies. The PSA values are mainly affected by prostate volume rather than age.

Usefulness of the (F/T)/PSA Density Ratio to Detect Prostate Cancer

INTRODUCTION

Prostate-specific antigen (PSA) is the most important marker in the detection of prostate cancer, but its reliability is limited by a low specificity. To improve the specificity of PSA, a new parameter, based on the combination of free/total PSA (F/T) with PSA density, is proposed.

MATERIALS AND METHODS

From April 1999 to June 2003, a series of 647 men with high serum PSA levels were submitted to ultrasound-guided multiple prostate biopsies. Total PSA and free PSA were measured by immunoassay (DASIT, Italy). Receiver operating characteristic (ROC) curves of PSA density, F/T and (F/T)/PSA density (F/T divided by PSA/prostate volume) were constructed, and relative specificity and sensitivity were calculated.

RESULTS

Prostate cancer was present in 284 cases (137 of them with PSA values between 4 and 10 ng/ml), 31 patientshad intraepithelial neoplasia and the remaining cases showed benign prostatic hyperplasia. Analysis of ROC curves in all examined patients showed that the area under the curve (AUC) for (F/T)/PSA density (0.849) was significantly higher than the AUC for F/T (0.681) (p = 0.012). Similar results were observed in the cases with PSA levels between 4 and 10 ng/ml, where the AUC for (F/T)/PSA density (0.768) was significantly higher than the AUC for F/T (0.610) (p = 0.041). In our study, the prostate cancer risk became very high when (F/T)/PSA density values decreased to <1.5.

CONCLUSION

The use of the (F/T)/PSA density ratio may be useful in the detection of prostate cancer, reducing unnecessary prostate biopsies. A cutoff of 1.5 for the (F/T)/PSA density value is recommended for patients with PSA levels between 4 and 10 ng/ml.

Update on screening for prostate cancer with prostate-specific antigen

Serum prostate-specific antigen (PSA) determination in conjunction with digital rectal examination (DRE) is recommended by the majority of clinical guidelines for early detection(opportunistic screening) of prostate cancer provided the patient is well informed and has a life-expectancy of at least 10 years. The major disadvantage of PSA is its lack of specificity. Various static and dynamic concepts have been developed to improve the diagnostic performance of PSA of which free/total PSA ratio and PSA doubling time seem to be the most promising. Apart from early detection, population screening(mass screening) is a distinct topic. The effect of the latter one with regard to reduction of prostate cancer specific mortality and quality of life issues is not yet clear. Several national and international prospective trials are currently being conducted to answer these important questions but results will only be available in a few years.

[Value of prostate-specific antigen density and transitional-zone prostate-specific antigen density in the diagnosis of prostate cancer]

INTRODUCTION

With serum prostate specific antigen (PSA) levels of 4.1 to 10 ng/ml a significant number of patients are unnecessary subjected to biopsy. We try to determine if the calculation of prostate specific antigen density (PSAD) and prostate specific antigen density of the transition zone (PSADTZ) improve the capacity to discriminate between non-malignant disease and prostate cancer.

METHODS

A prospective study including 314 males with PSA levels between 4.1 and 10 ng/ml is reported. Transrectal ultrasonography and prostatic biopsy were performed in all of them and total prostate and transition-zone volumes were calculated. PSA density and PSA density of the transition zone were calculated for each patient. Receiver operating characteristics (ROC) curves for PSA, PSAD and PSADTZ were constructed for all the patients and for those patients with digital rectal examination unsuspicous of malignancy, determining the sensitivity and specificity for several cutoff values.

RESULTS

The area under the curve for both, PSAD and PSADTZ, were greater than for PSA (p < 0.05), without any significant differences between PSADTZ and PSAD. The cutoff value of greatest diagnostic efficiency for PSAD was 0.17 ng/ml/cc (71.4% sensitivity and 55.7% specificity), while it was 0.41 ng/ml/cc for DPSATZ (70% sensitivity and 61.5% specificity). For those cases of normal digital rectal examination, no differences were observed between PSA and PSAD but they were between PSA and PSADTZ. In any event, the area under ROC curves was always less than 0.7, and, in order to avoid a large number of biopsies (high specificity), a large number of cancers are left without diagnosis (low sensitivity).

CONCLUSIONS

We conclude that PSAD and PSADTZ are not excessively useful for adequately discriminating between patients with prostate cancer and those with non-malignant disease, particularly when digital rectal examination is normal.

Prostate specific antigen complexed to alpha-1-antichymotrypsin in patients with intermediate prostate specific antigen levels

BACKGROUND

The authors attempted to evaluate prospectively the usefulness of serum prostate specific antigen (PSA) complexed to alpha-1-antichymotrypsin (PSA-ACT) in the early detection of prostate carcinoma and its ability to discriminate between prostate carcinoma and benign prostatic hyperplasia (BPH), especially among patients with intermediate PSA levels.

METHODS

Between December 1999 and August 2000, systematic sextant biopsies were performed on 281 prospective patients with prostate carcinoma who had serum PSA levels between 4.1 ng/mL and 20.0 ng/mL. The serum samples were assayed by using kits that were designed specifically for measuring serum PSA, PSA-ACT, and free PSA levels. The clinical values of PSA, PSA-ACT, the free PSA to total PSA ratio (F/T ratio), the free PSA to PSA-ACT ratio, PSA density (PSAD), and PSA-ACT density (ACTD) were compared by using receiver operating characteristic (ROC) curve analysis.

RESULTS

Biopsy yielded no evidence of malignancy in 198 patients, and prostate carcinoma was confirmed in 83 patients. ROC analysis demonstrated that the area under the curve (AUC) for PSA-ACT was greater than that for total PSA and was equivalent to that for the F/T ratio in both groups of patients (PSA ranges of 4.1-20.0 ng/mL and 4.1-10.0 ng/mL, respectively). The AUC for the ACTD was greater than the AUC for the PSAD and had the highest value of all parameters.

CONCLUSIONS

The measurement of PSA-ACT represents an alternative to the use of total and free PSA. The ACTD value is the most useful for discriminating between BPH and prostate carcinoma.

Prostate specific antigen adjusted for transition zone volume: the most powerful method for detecting prostate carcinoma

BACKGROUND

Several methods for the identification of patients with prostate carcinoma have been proposed to enhance the clinical usefulness of prostate specific antigen (PSA). However, it remains unclear which method is superior in practical use. The authors attempted prospectively to identify the most powerful method with which to detect prostate carcinoma, especially among patients with intermediate PSA levels.

METHODS

Between October 1997 and August 1999, systematic sextant biopsies were performed on 281 patients, including 147 with PSA levels between 4.1 ng/mL and 10.0 ng/mL. The clinical values of PSA, the free PSA to total PSA ratio (free/total PSA ratio), alpha-1-antichymotrypsin-PSA complex (PSA-ACT), the calculated derivatives, PSA density (PSAD), and PSA density of the transition zone (PSATZD) for the detection of prostate carcinoma were compared by using receiver operating characteristic (ROC) curves and logistic regression analyses.

RESULTS

According to ROC curve analysis, PSATZD had the greatest area under the curve in the overall patient population and in patients with intermediate PSA levels. In patients with intermediate PSA levels, at the sensitivity of 90%, PSATZD would have prevented unnecessary biopsies in 68 of 117 patients who were without prostate carcinoma, whereas PSA, free/total PSA ratio, and PSA-ACT would have prevented unnecessary biopsies in 25, 28, and 25 patients, respectively. Stepwise logistic regression analysis showed that PSATZD and findings on digital rectal examination were significant independent predictors.

CONCLUSIONS

PSATZD had the most useful validity in the differentiation between prostate carcinoma and benign prostatic enlargement in the overall patient population and in patients with intermediate PSA levels.

The pattern of serum markers in patients with androgen-independent adenocarcinoma of the prostate

In this exploratory study, our objectives were to correlate the serum and bone marrow concentrations of putative markers of prostate cancer progression in patients with advanced androgen-independent prostate cancer (AIPC), to assess the frequency and quantity of relative expression of these markers, and to correlate the expression of the markers with extent of disease (EOD) and overall survival. In a cohort of 50 patients with AIPC with bone metastases, we obtained serum and bone marrow samples and measured prostate specific antigen (PSA), serum interleukin-6 (sIL-6), bone marrow interleukin-6, serum chromogranin A (sCgA), bone marrow chromogranin A, and prostate specific membrane antigen (PSMA) by immunoassays. EOD was determined by quantifying identifiable bone lesions on radionuclide bone scans. Each variable was categorized into two groups (low and high) based on the median found in this cohort or on the cutoff based on normal limits when available. Analyses were performed in two subsets of patients with EOD either <20 or >/=20. Results showed that: (1) PSA is associated with EOD but not with outcome; (2) sIL-6 and sCgA may be intermediate markers of early progression in AIPC, because they are predictive of outcome only in patients with EOD <20; (3) elevated PSMA is associated with elevated sIL-6 but not with PSA, suggesting that PSMA may be a useful marker in AIPC; and (4) the ratio of PSA to putative markers of progression may reflect the complex clonal progression of prostate cancer. We conclude that patients with advanced AIPC exhibit one of two patterns of serologic marker expression: in some patients the disease status is reflected by PSA, and in others it is reflected by other markers. If these data are prospectively confirmed, this would help group patients with advanced AIPC into clinically relevant categories.

"BPSA," a specific molecular form of free prostate-specific antigen, is found predominantly in the transition zone of patients with nodular benign prostatic hyperplasia

OBJECTIVES

The biologic mechanism for the increased proportion of noncomplexed ("free") prostate-specific antigen (PSA) found in the serum of patients with benign prostate disease is unknown. We recently reported that most of the PSA found in benign, hyperplastic, and cancerous prostatic tissue is in the free form. To determine whether specific molecular forms of free PSA are associated differentially with normal, hyperplastic, or cancerous prostatic tissue, we have further characterized the free PSA in each type of prostatic tissue.

METHODS

PSA was purified by immunoaffinity chromatography from matched prostatic tissue samples of peripheral zone cancer (PZ-C), PZ noncancer (PZ-N), and transition zone (TZ) tissue from 10 large-volume (greater than 50 g) and 8 small-volume (less than 25 g) radical prostatectomy specimens. Eight TZ specimens obtained during transurethral resection of the prostate for benign prostatic hyperplasia (BPH) were also analyzed. The different molecular forms of PSA were further resolved by high-performance hydrophobic interaction chromatography. Clipped forms of PSA were identified by N-terminal amino acid sequencing.

RESULTS

More than 99% of the PSA in prostatic tissues was in the free, noncomplexed form. Specimens from the prostate TZ were found to contain elevated levels of an altered form of PSA, which we designated BPSA. Purified BPSA contained a distinctive cleavage at lysine 182. The median percent BPSA (%BPSA) was 11.4 in the TZ of specimens with nodular BPH compared with a %BPSA of 4.1 in the TZ of specimens without nodular BPH (P <0.0014). The median %BPSA levels of the PZ-N and PZ-C tissues ranged from 3.2 to 4.9 and were not significantly different from one another or from the %BPSA level of TZ tissues without nodular BPH.

CONCLUSIONS

We have identified a specific molecular form of clipped free PSA, called BPSA, that is increased within the prostatic TZ of patients exhibiting nodular BPH. Higher levels of percent free PSA in serum have been found to correlate strongly with prostate volume, which in turn is closely associated with the progressive enlargement of nodular BPH tissue within the TZ of the prostate. Thus, it is possible that a proportion of the serum percent free PSA found in patients with BPH may be composed of BPSA released into the serum.

Prostate-specific antigen

Prostate-specific antigen (PSA) has revolutionized the diagnosis and management of men with prostate cancer. Significant advances have been made since the early development of immunoassays. While PSA is useful for staging and monitoring of established disease, it has shown the greatest utility in the realm of early detection realm. PSA is the most important tumor marker; its importance in evaluating men for the possibility of prostate cancer is irrefutable. Enhancing specificity is a pressing need. In this regard, the recognition of the molecular forms of free PSA and complex PSA have shown the most promise and undoubtedly will result in fewer false-positive PSA test results. The salient literature is reviewed and commentary made on the current status of PSA with particular emphasis on methods to enhance its specificity in early detection and applications.

Estimation of Prostate Cancer Probability by Logistic Regression: Free and Total Prostate-specific Antigen, Digital Rectal Examination, and Heredity Are Significant Variables

Background: Despite low specificity, serum prostate-specific antigen (PSA) is widely used in screening for prostate cancer. Specificity can be improved by measuring free and total PSA and by combining these results with clinical findings. Methods such as neural networks and logistic regression are alternatives to multistep algorithms for clinical use of the combined findings.

Methods: We compared multilayer perceptron (MLP) and logistic regression (LR) analysis for predicting prostate cancer in a screening population of 974 men, ages 55–66 years. The study sample comprised men with PSA values &gt;3 μg/L. Explanatory variables considered were age, free and total PSA and their ratio, digital rectal examination (DRE), transrectal ultrasonography, and a family history of prostate cancer.

Results: When at least 90% sensitivity in the training sets was required, the mean sensitivity and specificity obtained were 87% and 41% with LR and 85% and 26% with MLP, respectively. The cancer specificity of an LR model comprising the proportion of free to total PSA, DRE, and heredity as explanatory variables was significantly better than that of total PSA and the proportion of free to total PSA (P &lt;0.01, McNemar test). The proportion of free to total PSA, DRE, and heredity were used to prepare cancer probability curves.

Conclusion: The probability calculated by logistic regression provides better diagnostic accuracy for prostate cancer than the presently used multistep algorithms for estimation of the need to perform biopsy.

Prostate cancer detection: relationship to prostate size

OBJECTIVES

It has been suggested that the lower detection rate for cancer in large prostates is due to the smaller proportion of tissue sampled. To examine this hypothesis, we evaluated whole-mount radical prostatectomy specimens in which the volume of cancer had been determined. We correlated cancer volume to overall gland volume. In addition, we performed stochastic computer simulations of parasagittal sextant biopsies on the same group of radical prostatectomy specimens. We correlated the likelihood of a positive cancer biopsy simulation with tumor volume and gland size.

METHODS

Six hundred seven tumor foci from 180 serially sectioned whole-mount prostatectomy specimens were mapped and digitized. Tumor volume was calculated by a step-section planimetry algorithm. Before sectioning, each gland was weighed. Systematic parasagittal sextant biopsies were computer simulated for each case. For each prostate, 40 simulations were performed, with random variations in biopsy location programmed for each run. Overall cancer detection by biopsy was considered positive if 90% of the 40 simulation runs were positive for cancer. Chi-square tests were used to evaluate statistical significance.

RESULTS

Small-volume cancers (0.5 cc or less) were twice as frequent in large glands greater than 50 g (P = 0.03). These small-volume tumors comprised 33% (13 of 40) of cancers in prostates greater than 50 g, 16% (5 of 31) in glands less than 30 g, and 14% (15 of 109) in glands 30 to 50 g. The rate of positive sextant biopsy simulation was lower in glands greater than 50 g than in glands 50 g or less (48% versus 67%, P<0.03). Smaller cancers were much less likely to be detected in the simulations. The simulation detection rate for cancers 0.5 cc or less was 18% (6 of 33), compared with a detection rate of 73% (107 of 147) for cancers greater than 0.5 cc (P<0.00001).

CONCLUSIONS

The observed lower cancer detection rate in large glands is a result of the higher proportion of low-volume cancers in these glands. This suggests that large prostates are more likely to be biopsied because of an elevated prostate-specific antigen value resulting from benign elements of the gland and not from a significant cancer. Increasing the number of cores solely to compensate for increased prostate size risks a disproportionate increased detection of small-volume tumors with a low clinical likelihood of progression.

Prostate-specific antigen

Prostate specific antigen (PSA) is serine protease produced at high concentrations by normal and malignant prostatic epithelium. It is mainly secreted into seminal fluid, where it digests the gel forming after ejaculation. Only minor amounts of PSA leak out into circulation from the normal prostate, but the release of PSA is increased in prostatic disease. Thus PSA is a sensitive serum marker for prostate cancer but its specificity is limited by a high frequency of falsely elevated values in men with benign prostatic hyperplasia (BPH). Approximately two-thirds of all elevated values (>4 microg/l) in men over 50 years of age are due to BPH. In serum, most of the PSA immunoreactivity consists of a complex between PSA and alpha1-antichymotrypsin (PSA-ACT) whereas approximately 5-40% are free. The proportion of PSA-ACT is larger and the free fraction is smaller in prostate cancer than in benign prostatic hyperplasia (BPH). Determination of the proportion of free PSA has become widely used to improve the cancer specificity of PSA especially in men with PSA values in the 'grey zone' (4-10 microg/l). PSA also occurs in complexes with other protease inhibitors and determination of these and other markers may further improve the diagnostic accuracy for prostate cancer. Interpretation of the results for many different markers is complicated, but this can be simplified by using statistical methods. The diagnostic accuracy can be further improved by using logistic regression or neural networks to estimate the combined impact of marker results and other findings like digital rectal examination (DRE), transrectal ultrasound (TRUS) and heredity.

Characterization of Monoclonal Antibodies for Prostate-specific Antigen and Development of Highly Sensitive Free Prostate-specific Antigen Assays

Background: The recent elucidation of the importance of serological free prostate-specific antigen (PSA) in the diagnosis of prostate cancer has created a demand for immunoassays specific for free PSA.

Methods: We developed and characterized 11 monoclonal antibodies with high affinities for PSA (Kavalues from 1.1 × 108 to 1.8 × 1010L/mol), only 3 of which cross-react with human glandular kallikrein (hK2). Using these antibodies and PSA antibodies developed by others, in conjunction with time-resolved fluorometry, we developed ultrasensitive sandwich immunoassays specific for the free form of PSA.

Results: The analytical detection limit of these immunoassays is 0.001 μg/L. To our knowledge, this is the most sensitive free PSA assay reported to date. The free PSA immunoassays exhibit &lt;1% cross-reactivity with PSA-α1-antichymotrypsin, show no cross-reactivity with hK2, and correlate well with established free PSA kits. The 11 antibodies developed by our group, in conjunction with 4 commercially available antibodies, were used to generate a putative epitope map of the PSA molecule.

Conclusion: The highly sensitive free PSA immunoassays may be used for measuring PSA subfractions in female serum, an application currently impossible with other reported free PSA immunoassays.

Advantages of replacing the total PSA assay with the assay for PSA-alpha 1-antichymotrypsin complex for the screening and management of prostate cancer

Several advantages become immediately apparent when the prostate specific antigen (PSA, or tPSA) assay is replaced by the assay specific for the serum PSA-alpha 1-antichymotrypsin (PSA-ACT) complex. For instance, random contributions to the tPSA value by various serum minor PSA isoforms can be avoided, making possible the determination of a more accurate relation of the PSA-ACT concentration to the tumor activity. Discrepancies in percent free PSA (% fPSA) values from the same specimens due to the use of different commercial kits also can be eliminated, mainly because the PSA-ACT assay does not have the problems in antibody selection and calibrator preparation usually associated with the tPSA assay. We found that at the present time different cutoffs of % fPSA for the differentiation of BPH from prostate cancer must be established for each individual tPSA assay. Cutoffs established using values from one tPSA assay should not be used for making clinical decisions when their tPSA values are determined by a different kit. Moreover, when we monitored the patients during treatment with serum tPSA, specific fPSA, and specific PSA-ACT complex assays simultaneously, it was clear that any interpretation of the patient's clinical status based on tPSA values alone could be misleading. Because there is less PSA-ACT complex in BPH specimens relative to that found in cancer serum samples, expressing fPSA as "fPSA/PSA-ACT x 100" and measuring PSA-ACT complex concentrations instead of tPSA during screening improve the measurable contrast between BPH and prostate cancer. Although individually modest, collectively these advantages can add up to considerable improvements.

Comparison of prostate-specific antigen corrected for total prostate volume and transition zone volume in a population-based screening study

OBJECTIVES

To compare the discriminatory potential between prostate cancer and benign conditions of the prostate in a population-based screening study, of serum prostate-specific antigen levels (PSA) and PSA corrected for both the total prostate volume (PSA-D) and the transition zone volume (PSA-T).

METHODS

In a randomized population-based screening study (Rotterdam section of the European Randomized Study of Screening for Prostate Cancer), in which 10,865 men have been screened, the biopsy results of 1202 men with PSA levels of 4 ng/mL or more were evaluated. Planimetric and prolate ellipsoid volumes of the total prostate as well as of the transition zone were measured. The measured volumes were compared with the volumes of 57 radical prostatectomy specimens through Spearman's rank correlation coefficient and agreement tests. A receiver operating characteristic (ROC) curve analysis was done of sensitivity and specificity of biopsy indications through PSA and PSA corrected for the volumes measured with transrectal ultrasound.

RESULTS

In the 1202 men studied, 361 cases of prostate cancer were diagnosed. Both PSA-D and PSA-T showed a significantly higher area under the ROC curve (0.77 and 0.79, respectively) than PSA alone (area 0.65). There was no significant difference between PSA-D and PSA-T. The use of a PSA-D threshold value of 0. 10 ng/mL/cc would have avoided 28% of biopsies at the cost of 10% of detectable cancers. A PSA-D threshold of 0.15 ng/mL/cc would have avoided 73.8% of biopsies at the cost of not diagnosing 43.8% of detectable cancers.

CONCLUSIONS

The planimetrically obtained prostate volume showed a more favorable agreement with the radical prostatectomy volume than the prolate ellipsoid volume. The discriminatory potential of the corrected PSA value is better at predicting the results of needle biopsy of the prostate when compared with PSA alone. The use of the transition zone volume for this correction results in a higher discriminatory potential when compared to the use of the total prostate volume; however, the observed difference was not statistically significant.

Relationship among age, prostate-specific antigen, and prostate volume in men with lower urinary tract symptoms (LUTS) and in different groups of men with and without benign and malignant prostate diseases

BACKGROUND

In order to enhance prostate-specific antigen (PSA) as a predictor of prostate cancer, it is necessary to understand the characteristics of this tumor marker in a population of men without evidence of prostate cancer but who are at risk for developing the condition.

METHODS

In an age-stratified population of 328 men with lower urinary tract symptoms (LUTS), we analyzed the distribution of PSA levels as a function of age and prostate volume, and we analyzed the percentage of age-related variance in PSA that can be explained by the age-related variance in prostate volume.

RESULTS

Classifying the 328 cases with LUTS according to four age groups, a correlation was found between PSA and prostate volume, becoming stronger from the younger (correlation coefficient, -0.1265) to the older group (correlation coefficient, 0.6044). Serum PSA variance per milliliter of prostate volume also increased from the younger (not significant, P > 0.1) to the older age decades (7.3% in men age 70 years or over). Moreover, the results of the regression analysis suggest that 10% of the variance in PSA with age can be accounted for by prostate volume in men under age 50 years, reaching 37% in men age 70 years or more.

CONCLUSIONS

These data confirm that the serum PSA concentration increases with advancing age in the absence of clinically evident prostatic malignancy. In younger patients with LUTS, serum PSA variance with age seems to be less dependent upon the age-related variance in prostate volume.

Prostate-specific antigen density

Nearly 20 years have passed since PSA was definitively identified. Throughout this period, its clinical application as a tumor marker has expanded significantly. Today, besides monitoring prostate cancer therapy, PSA is being used extensively in mass screening programs for early detection of adenocarcinoma of the prostate and has become the most important tumor marker in urologic oncology. Although of unquestionable importance, PSA is not the perfect marker because of its lack of efficacy in discriminating BPH from prostate cancer. In order to enhance its sensibility, specificity, and predictive value, a series of variables influencing PSA levels have been studied and new parameters developed to correct discrepancies or confounding factors. Recognition of the relationship between PSA, prostate volume, and their interference with serum PSA levels made possible the development of the PSAD concept. Its wide application in different sets of patients for diagnostic and staging purposes resulted in enough data to demonstrate its usefulness and cost effectiveness as a second-line screening parameter, helping to distinguish BPH from prostate cancer in patients with PSA levels in the intermediate area, and avoiding some unnecessary biopsies. Even though PSAD does not offer a definitive solution for prostate cancer screening or management, its association with all the other diagnostic methods may offer the best way to assess the population at risk and assure their well-being (Fig. 5).

Comparative analysis of prostate specific antigen and its indexes in the detection of prostate cancer

PURPOSE

Prostate specific antigen (PSA) density and age referenced PSA have been proposed in an attempt to improve the power of PSA in the detection of early prostate cancer. Reported results have been controversial and disappointing. Because the association of gland volume with PSA is stronger than that of age we developed a new index, volume referenced PSA, and compared it to PSA density and other indexes.

MATERIALS AND METHODS

Volume referenced PSA was developed from a control group of 408 men without clinical evidence of prostate cancer using a standardized Z score. A retrospective analysis was performed comparing PSA and all its indexes in 580 men who underwent prostate biopsy. In addition to overall analysis, PSA and its indexes were evaluated with receiver operating characteristic curves by age and volume subcategories.

RESULTS

Cancer was identified in 35% of the 580 men. The number of missed cancers using established thresholds significantly favored volume referenced PSA clinically and statistically compared to all other indexes but it was equivalent to PSA alone clinically. Age referenced PSA prevented more biopsies from being done than did volume referenced PSA (39% versus 31%) but resulted in the diagnosis of 48% fewer cancers. Receiver operating characteristic curve analysis demonstrated a significantly better performance for volume referenced PSA and PSA density compared to PSA alone and age referenced PSA.

CONCLUSIONS

Volume based PSA indexes are superior to PSA and age referenced PSA statistically. However, clinically volume referenced PSA is comparable to PSA, and both are superior to age referenced PSA and PSA density in the detection of prostate cancer.

PSA divergence. A new parameter for the accurate longitudinal assessment of prostatic disease

Prostate-specific antigen (PSA) and the various parameters derived utilizing this marker have increased our ability to diagnose early prostatic disease; however, their accuracy in identifying the etiology of the disease remains somewhat limited. We propose a new PSA derivative, termed "PSA divergence" (PSADI), defined as the change in serum PSA over time (years) divided by the change in prostatic volume over time (years), to more accurately distinguish benign, premalignant, and malignant prostatic diseases. In this study, we evaluated 160 subjects with a PSA >4.0 ng/ml who were found by transrectal ultrasound-guided biopsy (TRUS) to have either benign prostatic hyperplasia or prostatic intraepithelial neoplasia. These men were followed at 6 or 12 months with serial PSA, digital rectal exam (DRE), and TRUS with rebiopsy. Data analysis demonstrated a statistically significant (p < 0.05) correlation between PSADI and each final pathologic outcome, suggesting that PSADI is useful in distinguishing among intraepithelial neoplasia and benign and malignant prostatic disease.

A guide to the interpretation of serum prostate specific antigen levels

OBJECTIVE

To review the factors that affect the concentration of prostate specific antigen (PSA) in the serum.

RESULTS

The discussion includes the structure of PSA; its distribution and metabolism; various analytical aspects of PSA measurements; the effects of clinical manipulations on PSA, including digital rectal examination, transrectal ultrasound, cystoscopy, biopsy and transurethral resection of the prostate; factors affecting PSA levels in health, in benign disease, and in prostate cancer; the effect of various treatments on PSA; and the issue of reference ranges.

CONCLUSION

Laboratory staff and physicians must take many factors into consideration when interpreting PSA results.

Serum concentrations of prostate specific antigen and its complex with alpha 1-antichymotrypsin before diagnosis of prostate cancer

Prostate cancer can be detected at an early, potentially curable stage by screening based on digital rectal examination and serum prostate specific antigen (PSA). The value of screening appears doubtful, based on high 10-year survival rates in selected cases of early prostate cancer, but this follow-up time may be insufficient. By linking the information on 21172 men who took part in a screening examination in Finland, 1968-73, with data from the Finnish Cancer Registry, 44 cases of prostate cancer diagnosed up to 1980 were identified. Serum samples from cancer cases and from 74 controls matched for age and time of sampling were assayed for PSA and its complex with alpha 1-antichymotrypsin (PSA-ACT). With a cut-off for PSA of 2.5 micrograms/L giving 92% specificity, 95% of the cancers developing within the first 5 years, and 52% developing in 6-10 years tested positive. As a potential screening test with a 5-year interval for men under 65, the sensitivity would be 92% and specificity 97%. The ratio of PSA-ACT to total PSA was lower in controls than in patients with cancer. Using this ratio, we could eliminate half of the false-positive results in the range 2.5-25 micrograms/L without loss of sensitivity. Cancer was typically diagnosed 5-10 years after PSA exceeded 2.5 micrograms/L, and the median survival after diagnosis was 3.6 years. 10-year survival after drawing the sample was 71% in cancer cases with a PSA concentration less than 4 micrograms/L and 48% in those with higher concentrations. The corresponding figures at 15 years were 53% and 27%, and at 20 years 43% and 18%, respectively. These results suggest it is advisable to confine screening for prostate cancer to men with a life expectancy of clearly more than 10 years--ie, younger men, who have the greatest chance to benefit from early detection.

Influence of benign prostatic hyperplasia, testosterone and age on serum levels of prostate specific antigen

Prostate specific antigen (PSA) and PSA-density (PSAd) were studied in 120 symptomatic patients with benign prostatic hyperplasia at digital rectal examination. PSA and PSAd were measured before and 3 months after transurethral resection. Comparisons were made between patients in whom histologic examination showed benign hyperplasia and those with histologically demonstrated prostatic cancer. The influence of age and of serum testosterone on PSA and PSAd was determined. PSAd in benign prostatic hyperplasia was the same in the transition zone (the adenomas) and the peripheral zone (mean 0.065), indicating no increased synthesis or leakage of PSA. PSAd with cut-off value 0.10 ng x ml-1 x cc-1 showed higher sensitivity and positive predictive value (75% vs 50% and 0.33 vs 0.15, respectively) in nonpalpable prostatic cancer than did PSA with cut-off at 4 ng x ml-1. No statistically significant influence of testosterone and/or age on serum-PSA or PSAd was found.

Prostate specific antigen and prostate specific antigen density. Roles in patient evaluation and management

Prostate specific antigen (PSA) is the most accurate serum marker for prostate cancer. However, sensitivity and specificity are suboptimal, especially at the intermediate levels between 4.1 and 10.0 ng/ml (monoclonal). For intermediate PSA levels, PSA density (PSAD) provides unique information regarding the need for biopsy and the likelihood of prostate cancer. The authors prospectively used PSAD to determine the need for biopsy in 68 patients with PSAD values below 0.150 and normal results from a digital rectal examination. Ten patients have undergone biopsy secondary to a rising serum PSA. Three were found to harbor prostate cancer and have undergone therapy. The remaining 65 patients continue on surveillance. PSAD can predict treatment outcomes for patients with clinically localized prostate cancer treated with radical prostatectomy. PSADs at low values are 90% accurate in predicting operative success. PSADs at high values are 67% accurate in predicting failure. Cancer 1994; 74: 1667-73.