Sensitive Prostate Specific Antigen Measurements Identify Men With Long Disease-Free Intervals and Differentiate Aggressive from Indolent Cancer Recurrences within 2 Years After Radical Prostatectomy

Prostate-Specific Antigen as an Ultrasensitive Biomarker for Patients with Early Recurrent Prostate Cancer: How Low Shall We Go? A Systematic Review

Serum prostate-specific antigen (PSA) needs to be monitored with ultrasensitive PSA assays (uPSAs) for oncologists to be able to start salvage radiotherapy (SRT) while PSA is <0.5 µg/L for patients with prostate cancer (PCa) relapsing after a radical prostatectomy (RP). Our systematic review (SR) aimed to summarize uPSAs for patients with localized PCa. The SR was registered as InPLASY2023110084. We searched for studies on Google Scholar, PUBMED and reference lists of reviews and studies. We only included studies on uPSAs published in English and excluded studies of women, animals, sarcoidosis and reviews. Of the 115 included studies, 39 reported PSA assay methods and 76 reported clinical findings. Of 67,479 patients, 14,965 developed PSA recurrence (PSAR) and 2663 died. Extremely low PSA nadir and early developments of PSA separated PSAR-prone from non-PSAR-prone patients (cumulative p value 3.7 × 1012). RP patients with the lowest post-surgery PSA nadir and patients who had the lowest PSA at SRT had the fewest deaths. In conclusion, PSA for patients with localized PCa in the pre-PSAR phase of PCa is strongly associated with later PSAR and survival. A rising but still exceedingly low PSA at SRT predicts a good 5-year overall survival.

Utility of a Fifth-Generation Ultrasensitive Prostate-Specific Antigen Assay for Monitoring Prostate Cancer Patients after Radical Prostatectomy with 3 Years of Follow-Up

BACKGROUND

We investigated an ultrasensitive prostate-specific antigen (uPSA) immunoassay (MesoScale; lower limit of detection (LLD) of 0.0035 pg/mL) to monitor patients with prostate cancer (PCa) following radical prostatectomy (RP) and to examine whether changes in PSA in the conventionally undetectable range (<1 pg/mL) can predict biochemical relapse (BCR).

METHODS

We measured uPSA in serial serum samples (N = 100) collected from 20 RP cases with a third-generation ELISA (LLD of 1 pg/mL) and the fifth-generation MesoScale assay. We analyzed the PSA nadir changes to classify patients into BCR or non-BCR groups, observed the trends in PSA kinetics, and associated BCR status with clinicohistopathological features.

RESULTS

The ELISA could quantify PSA in only 38% of the RP samples, detecting BCR in 7 of 20 patients with PCa. The MesoScale assay quantified PSA in all samples, showing 8 of 20 patients with BCR. However, there was no significant difference between the median time to BCR detection based on ELISA (1016 days) compared with MesoScale data (949 days). Gleason scores were higher in the BCR groups compared with non-BCR. There was no significant difference for other clinicohistopathological parameters.

CONCLUSIONS

The uPSA MesoScale technology could track miniscule changes in serum PSA in the range of 0.003-1 pg/mL in all RP cases. However, PSA kinetics and nadir at concentrations <2 pg/mL fluctuated, and increases below this range could not reliably suggest signs of BCR. Instead, ultrasensitive fifth-generation PSA assays may hold clinical potential for measuring the low concentrations of PSA in women for various medical contexts.

Nucleic Acid Detection Immunoassay for Prostate-Specific Antigen Based on Immuno-PCR Methodology

BACKGROUND

Serum prostate-specific antigen (PSA) concentrations after radical prostatectomy typically become undetectable with the use of current immunometric assay methods. Despite modern surgical techniques, 15%–30% of prostate cancer patients undergoing radical prostatectomy develop a biochemical recurrence during follow-up. Unfortunately, poor analytical sensitivity of standard PSA assays delays biochemical recurrence detection, and because of day-to-day assay imprecision ultrasensitive PSA assays cannot assess PSA kinetics. We developed an immuno-PCR assay for total PSA that has a limit of quantification &gt;10 times lower than current ultrasensitive assays.

METHODS

The 2-site immunometric assay for total PSA employed 2 monoclonal antibodies, one conjugated to a double-stranded DNA label and the other bound to paramagnetic microparticles. After several washing steps, quantification cycles were determined and values were converted to PSA concentrations. We characterized analytical performance and compared accuracy with a commercially available total PSA assay.

RESULTS

The limit of quantification was 0.65 ng/L and the assay was linear in the range of 0.25–152.0 ng/L. Total imprecision estimates at PSA concentrations of 3.8, 24.1, and 69.1 ng/L were &lt;15.2%, &lt;9.4%, and &lt;10.6%, respectively. Recovery of supplemented PSA ranged from 87.5% to 119.2% (mean 100.3%). Dilution recovery ranged from 96.4% to 115.3% (mean 102.3%). There was no high-dose hook effect up to 50 000 ng/L of PSA. Comparison with the commercial PSA assay showed a regression slope of 1.06 and a correlation coefficient of 0.996.

CONCLUSIONS

The analytical characteristics of the assay support the use of this assay for the accurate and precise measurement of serum PSA, even at sub–nanogram-per-liter concentrations.

Can early implementation of salvage radiotherapy for prostate cancer improve the therapeutic ratio? A systematic review and regression meta-analysis with radiobiological modelling

PURPOSE

For prostate cancer that is thought to be locally recurrent after prostatectomy, the optimal timing, dose and techniques for salvage radiotherapy (SRT) have not been established. Here we perform a systematic review of published reports including regression meta-analysis and radiobiologic modelling to identify predictors of biochemical disease control and late toxicity.

METHODS

We performed a review of published series reporting treatment outcomes following SRT. Studies with at least 30 patients, median PSA before SRT of less than 2.0 ng/mL, and median follow-up of greater than 36 months were identified. Univariate and multivariate analyses were performed to test Gleason Score, SRT dose, SRT timing, pre-SRT PSA, whole pelvic irradiation and androgen deprivation therapy as predictors of 5-year biochemical progression-free survival (bPFS) and severe (grade≥3) late GI and GU toxicity. bPFS and toxicity data were fit to tumour control probability and normal tissue complication probability models, respectively.

RESULTS

Twenty-five articles met the inclusion criteria for this analysis. Five-year bPFS ranged from 25% to 70%. Severe late GI toxicity rates were 0% to 9%, and severe late GU toxicity rates were 1-11%. On multivariate analysis, bPFS increased with SRT dose by 2.5% per Gy and decreased with pre-SRT PSA by 18.3% per ng/mL (p<0.001). Late GI and GU toxicity increased with SRT dose by 1.2% per Gy (p=0.012) and 0.7% per Gy (p=0.010), respectively. Radiobiological models demonstrate the interaction between pre-SRT PSA, SRT dose and bPFS. For example, an increase in pre-SRT PSA from 0.4 to 1.0 ng/mL increases the SRT dose required to achieve a 50% bPFS rate from 60 to 70Gy. This could increase the rate of severe late toxicity by approximately 10%.

CONCLUSION

Biochemical control rates following SRT increase with SRT dose and decrease with pre-SRT PSA. Severe late GI and GU toxicity rates also increase with SRT dose. Radiobiological models suggest that the therapeutic ratio of SRT may be improved by initiating treatment at low PSA levels.

Clinicopathological features of patients with biochemical recurrence after radical prostatectomy without progressive rise in serum prostate-specific antigen

INTRODUCTION

The objective of this study was to characterize clinicopathological features of patients with biochemical recurrence after radical prostatectomy who did not exhibit a progressive rise in serum prostate-specific antigen (PSA) during the follow-up period.

MATERIALS AND METHODS

We analyzed data from 162 consecutive patients who underwent radical prostatectomy for clinically organ-confined prostate cancer without neoadjuvant hormonal therapy and were followed postoperatively for at least 1 year. The serum PSA value was measured using an ultrasensitive PSA assay system (Roche Diagnostics, Mannheim, Germany), and biochemical recurrence was defined as a serum PSA of >or=0.1 ng/ml.

RESULTS

A total of 32 patients (19.8%) were diagnosed as having biochemical recurrence. Among these patients, we identified 10 (31.3%) with a serum PSA>0.1 ng/ml who had not shown PSA or clinical progression during a median follow-up of 34 months after radical prostatectomy. In these 10 patients, the median time to biochemical recurrence was 17 months, the median PSA velocity after biochemical recurrence was 0.034 ng/ml/year, and there was no patient whose serum PSA value became >0.4 ng/ml. There were no clinicopathological parameters except for PSA velocity that were significantly associated with the features of these 10 patients.

CONCLUSION

Because of the presence of a subset of patients with biochemical recurrence after radical prostatectomy who will not show a progressive increase in serum PSA value, the indication for adjuvant therapy for such patients should be cautiously determined considering several factors, such as PSA kinetics.

Usefulness of the nadir value of serum prostate-specific antigen measured by an ultrasensitive assay as a predictor of biochemical recurrence after radical prostatectomy for clinically localized prostate cancer

INTRODUCTION

The objective of this study was to determine whether the nadir value of serum prostate-specific antigen (PSA) measured by an ultrasensitive assay could be a useful predictor of biochemical recurrence after radical prostatectomy for clinically localized prostate cancer.

MATERIALS AND METHODS

This study included 127 patients who underwent radical prostatectomy for clinically localized prostate cancer without neoadjuvant hormonal therapy and were pathologically diagnosed as negative for lymph node metastasis. The serum PSA value was measured using an ultrasensitive PSA assay system (Roche Diagnostics, Mannheim, Germany), and the findings were analyzed with respect to several clinicopathological factors. In this series, biochemical recurrence was defined as PSA persistently >0.2 ng/ml.

RESULTS

Based on the nadir PSA value, we divided 127 patients into three groups as follows: group A (n=99):<or=0.01 ng/ml; group B (n=16): 0.01-0.05 ng/ml, and group C (n=12): >or=0.05 ng/ml. The nadir PSA value was significantly associated with preoperative PSA value, but not other conventional clinicopathological prognostic parameters. During the observation period (median 31 months, range 6-75 months), biochemical recurrence occurred in 16 patients, that is, 1 in group A (6.3%), 4 in group B (25.0%), and 11 in group C (91.7%). Multivariate analysis using the Cox proportional hazards regression model indicated that the nadir PSA value was an independent predictor for biochemical recurrence after radical prostatectomy.

CONCLUSION

These findings suggest that the nadir serum PSA value measured by an ultrasensitive assay could be a useful predictor of biochemical recurrence after radical prostatectomy for clinically localized prostate cancer, and that careful follow-up should be considered in cases demonstrating a nadir PSA value>0.01 ng/ml because of the significantly higher probability of biochemical recurrence in such cases.

Biochemical Recurrence after Localized Treatment

The quoted incidence of biochemical recurrence (BCR) after localized treatment varies significantly and depends on numerous well-known prognostic factors; however, it likely occurs in at least 30%-40% of patients who receive localized treatment. Because the clinical significance of BCR is often unclear, and depends in many cases on unknown factors, it is difficult to select the best treatment and determine when best to institute that therapy. This review examines some of the issues associated with BCR and attempts to shed some light on this common but controversial clinical scenario. Some treatment strategies discussed in this article include salvage radiotherapy after radical prostatectomy, salvage therapy after radiotherapy, and hormonal therapy.

High serum prostate-specific antigen concentrations in hirsute women do not decrease with treatment by the combination of spironolactone and the contraceptive pill

Using an ultrasensitive assay, prostate-specific antigen (PSA) has been detected in female serum and has been proposed as a potential marker of androgen excess in hirsute women. Measurement of PSA levels in serum may play a role in monitoring hirsutism during antiandrogen therapy. We investigated the role of PSA as a marker of androgen activity in hirsute patients taking spironolactone together with oral contraceptive pills containing ethinyl estradiol and gestodene. Twenty-eight hirsute patients were included in the study. Clinical and biochemical variables including serum levels of PSA (using an ultrasensitive chemiluminscent immunoassay), dehydroepiandrosterone sulfate, total testosterone, free testosterone and 17-hydroxyprogesterone concentrations were recorded at baseline and after six cycles of treatment. Fifteen healthy women were included in the study as controls. Serum PSA levels in hirsute women were clearly higher than in the control group (0.023 +/- 0.004 vs. 0.006 +/- 0.003 ng/ml, p < 0.001) and correlated with baseline serum free testosterone concentrations (r = 0.518, p = 0.005). After 6 months, serum PSA concentrations as compared with baseline values did not change significantly in patients who were given spironolactone plus contraceptive pills (p = 0.4) despite a marked decrease in total testosterone, free testosterone, 17-hydroxyprogesterone, dehydroepiandrosterone sulfate and hirsutism score (p < 0.05). Thus, serum PSA levels in hirsute women were higher than in non-hirsute healthy controls. A 6-month course of treatment with spironolactone combined with contraceptive pills containing ethinylestradiol and gestodene did not reduce high serum PSA levels in these subjects. In conclusion, the serum PSA level is not a convenient biochemical marker with the available assays for the management of hirsute women treated with the combination of spironolactone and oral contraceptives.

Regulation of prostate-specific antigen by activin A in prostate cancer LNCaP cells

Activins are multifunctional growth and differentiation factors and stimulate FSH-beta gene expression and FSH secretion by the pituitary gonadotropes. Follistatins bind activin, resulting in the neutralization of activin bioactivity. The activin/follistatin system is present in the prostate tissue. Prostate-specific antigen (PSA) plays an important role in male reproductive physiology as well as being very important as a tumor marker for prostate cancer. Thus the regulation of PSA has important clinical implications. Previous studies showed that PSA is primarily regulated by androgens. In the present study, we evaluated the direct effects of activin A on the proliferation and PSA production of prostate cancer LNCaP cells, which express functional activin receptors and androgen receptor and PSA. LNCaP cells were treated with activin A and 5alpha-dihydrotestosterone (DHT) with or without their antagonists (follistatin or the nonsteroidal anti-androgen bicalutamide). Activin A decreased cell growth of LNCaP cells in a dose-dependent manner, whereas DHT increased it in a biphasic manner. In contrast to their opposing actions on cell growth, both activin A and DHT upregulated PSA gene expression and increased PSA secretion by LNCaP cells. The effects of activin A and DHT to increase PSA production were synergistic or additive. Follistatin or bicalutamide was without effect on cell growth or PSA production. The effects of activin A on LNCaP cells were blocked by follistatin, not by bicalutamide, whereas effects of DHT were prevented by bicalutamide, not by follistatin. Activin A upregulates PSA production, and the effect is through an androgen receptor-independent pathway. The activin/follistatin system can be a physiological modulator of PSA gene transcription and secretion in the prostate tissue, and activins may cooperate with androgen to upregulate PSA in vivo.

How sensitive is a prostate-specific antigen measurement? How sensitive does it need to be?

Assays are now available that can measure very low concentrations of prostate-specific antigen (PSA), but their analytic performance and clinical utility are not well defined. This brief article highlights some of the clinical issues related to the limited prognostic significance of small changes in PSA concentrations in men with prostate cancer who have been treated with prostate ablation therapy. College of American Pathologists proficiency survey data are presented, illustrating the performance of commercial PSA assays with low PSA concentration survey samples tested between 1998 and 2002. The performance of the assays appears to be improving, but many of the currently used assays have intralaboratory coefficients of variation greater than 20% for PSA concentrations less than 0.4 ng/mL. Also, there are major differences in the level of PSA reported by various assays in these low concentration samples. These level differences (if they are also seen in clinical samples) may cause clinical problems when fixed serum PSA thresholds (eg, 0.2 ng/mL) are used to make clinical decisions related to prostate tumor recurrence.

Variables in predicting survival based on treating "PSA-only" relapse

Prostate cancer recurrence (after prior local treatment) that is detectable only by a rise in serum prostate specific antigen (PSA) level is a very common problem facing clinicians. Given that the majority of contemporary era men with PSA-only or biochemical recurrence are relatively young and otherwise healthy, treatment requires approaches that both improve clinical outcomes and preserve quality of life. Treatment is in one of two broad categories, additional local therapies, termed "salvage" local therapy and systemic therapies. For radical prostatectomy patients, salvage external beam radiotherapy to the prostate bed is commonly employed, being reserved for early biochemical recurrence in men with low risk at distant metastases. For primary radiation patients, salvage radical prostatectomy or cryotherapy can similarly be used for those men felt not to harbor distant metastases. Systemic therapy generally involves hormonal therapy. Traditional hormonal therapy (orchiectomy, luteinizing hormone-releasing hormone agonists, or maximum androgen blockade) is the current mainstay of systemic treatment for biochemical recurrence, although nontraditional approaches, such as antiandrogen monotherapy, are increasingly being used. Variables in predicting survival based on treating PSA relapse is problematic. The condition of biochemical failure has only been recognized in the last decade and few "PSA-era" patients with biochemical recurrence have actually died of disease. Hence, the validation of prediction variables in this setting is just emerging. Early work would suggest that timing of recurrence, Gleason grade, and PSA velocity or doubling time during relapse are important prognostic factors. New data on PSA doubling time will be presented.

Biochemical recurrence without PSA progression characterizes a subset of patients after radical prostatectomy. Prostate-specific antigen

OBJECTIVES

To characterize a subset of patients with biochemical recurrence after radical prostatectomy but with little, if any, subsequent rise in serum prostate-specific antigen (PSA) and no clinical progression during long-term follow-up.

METHODS

Of a series of 600 patients, 158 with biochemical recurrence after radical prostatectomy were examined. We identified a subset with measurable serum PSA levels during long-term follow-up, but with very low PSA velocity and no clinical recurrence. Serum PSA was measured with the ultrasensitive TOSOH assay with a PSA recurrence defined as a serum PSA of 0.07 ng/mL or greater.

RESULTS

We identified 14 patients (8.8% of biochemical recurrences) with a detectable serum PSA level after radical prostatectomy yet without clinical or PSA progression at a mean follow-up after radical prostatectomy of 10.3 years. The mean time to PSA recurrence was 5.8 years, and the mean PSA velocity after recurrence was 0.028 ng/mL/yr. No clinical or pathologic features were found that could be used to identify this subset of patients.

CONCLUSIONS

A subset of patients with biochemical recurrence after radical prostatectomy will not exhibit a progressive rise in serum PSA or clinical progression at 10 years follow-up. This suggests that serum PSA kinetics should be observed after biochemical recurrence before adjuvant hormonal therapy or radiotherapy.

Using splines to detect changes in PSA doubling times

BACKGROUND

PSA doubling time (PSADT) can predict the likelihood of clinical progression in patients with biochemical relapse after surgery or radiation for prostate cancer. Changes in PSA doubling time in response to therapy may be of clinical or investigational significance. How does one estimate PSADT before and after the initiation of therapy and determine if any change is statistically significant or simply the result of random variation? These are the type of questions addressed.

METHODS

Our technique uses a best-fitting spline (i.e., a broken-line approximation) to a graph of log PSA on time to estimate PSADTs before and after treatment initiation. A linear regression program is used to produce the fit and to evaluate the statistical significance of any change in PSADT. This method differs from previous methods in that it uses all the data, exploits the continuity of PSA at the time of treatment initiation, and allows one to make statistical significance statements about specific individuals.

RESULTS

Our technique is illustrated with data from a pilot clinical trial using a nutritional supplement in 12 men with prostate cancer. A detailed analysis of the first patient shows how the data are handled, how two lines of computer code are sufficient to fit the spline model, and how the doubling times and statistical significance of a change are read from the computer output. In the study, 9 of 12 patients had a statistically significant increase in doubling time. Because the study is preliminary and used only to illustrate our method, no medical discussion of the study is included. The last section of the study, in part expository, is devoted to explaining the underlying principles for those who may want to know not only what to do, but why it works.

CONCLUSIONS

The method presented here for determining changes in PSADT is both simple and broadly applicable. It allows the evaluation of the size and statistical significance of an observed change or increase in PSADT in response to therapy for prostate cancer. It can be done using essentially any statistical software and widely accepted statistical methods.

Relationship between serum prostate-specific antigen and calculated epithelial volume

OBJECTIVES

To estimate the relationship between serum prostate-specific antigen (PSA) and prostatic epithelial volume, a new simple method for measuring epithelial volume was developed and its efficacy evaluated in patients with benign prostatic hyperplasia.

METHODS

Between March 1998 and June 2001, 122 patients without prostate cancer in the transurethral resected specimen were enrolled in this study. Of the 122 patients, 55 had a serum PSA level of 4.0 ng/mL or greater and negative sextant biopsies before surgery. First, we measured the epithelium/glandular lumen ratio by computer image analysis in 20 specimens. Second, we measured the percentage of glandular lumen in all 122 patients. The prostatic epithelial volume was then calculated as follows: calculated epithelium volume (in cubic centimeters) = epithelium/glandular lumen ratio percentage of glandularlumen x total prostate volume (in cubic centimeters).

RESULTS

The epithelium/glandular lumen ratio was 1.01 in the 20 specimens. In the 122 patients with benign prostatic hyperplasia, the calculated epithelial volume correlated more strongly with the serum PSA level than did the total prostate volume, transition zone volume, or percentage of epithelium (gamma = 0.672, P <0.0001). The mean PSA level per calculated epithelial volume was 1.27 ng/mL/cm(3). The calculated epithelial volumes from the biopsy specimens correlated significantly with those from transurethral resection specimens (gamma = 0.956, P <0.0001).

CONCLUSIONS

Serum PSA levels correlated significantly with prostatic epithelial volumes in patients with benign prostatic hyperplasia. The method of measuring prostatic epithelial volume used in this study is very convenient for clinical practice.

Prostate-specific antigen in prostate cancer: a case study in the development of a tumor marker to monitor recurrence and assess response

The serum marker known as prostate-specific antigen (PSA) has established itself as the most important tool for the early detection of prostate cancer. However, more recent data indicate that (post-treatment) PSA and PSA kinetics can be used to predict the outcome of a variety of therapeutic interventions including radical prostatectomy, radiation therapy, androgen deprivation, and treatment of hormone-refractory prostate cancer. PSA recurrence after radiation therapy is now accepted as a harbinger of developing metastatic disease. The American Society for Therapeutic Radiation Oncology (ASTRO) consensus definition is the most widely accepted definition of failure after radiation therapy. Rather than using a specific PSA cutoff, three consecutive PSA rises was felt to be a more reliable indicator of biochemical failure. The PSA nadir (the lowest PSA level achieved after therapeutic intervention) also appears to correlate with the likelihood of remaining disease-free. Similarly, a rapid doubling time is a significant predictor of developing distant metastases. The most appropriate definition for biochemical (PSA) failure following radical prostatectomy is usually considered to be a non-zero value. As is the case after radiotherapy, there appears to be a relationship between the rate of rise of the PSA and the risk of distant failure following radical prostatectomy. In patients with metastatic disease, multiple studies appear to indicate that a fall in PSA, however measured, appears to be predictive of improved outcome in prostate cancer patients treated with androgen deprivation. Multiple reports of trials in the treatment of hormone-refractory prostate cancer (HRPC) appear to substantiate the observation that patients who have a greater than 50% decline in PSA have an improved survival. Correlation of PSA declines with other markers of clinical benefit, including clinically significant "subjective" end points such as pain control, have strengthened the argument that a PSA decline can serve as an intermediate endpoint in clinical trials involving HRPC patients.

Volume-weighted mean nuclear volume predicts tumor biology of clinically organ-confined prostate cancer

BACKGROUND

Estimates of volume-weighted mean nuclear volume (MNV) are the only means by which unbiased estimates of three-dimensional parameters can be obtained from a single two-dimensional section, with stereological methods. The present study was conducted to elucidate the role of MNV in predicting tumor biology for patients treated with radical prostatectomy.

METHODS

A retrospective prognostic study of 71 patients with T1/T2 disease, treated with radical prostatectomy alone, was performed. MNV was estimated using biopsy specimens based on a stereological method, and was compared with other preoperative clinical variables. For patients with prostate-specific antigen (PSA) failure, we determined the correlation of MNV with PSA doubling time (PSA DT) which was calculated using PSA values obtained with an ultrasensitive assay.

RESULTS

Mean MNVs for pathologically organ-confined and non-organ-confined tumors were 198.9 and 236.3 microm3, respectively; this difference was significant (P = 0.0364). Univariate analysis showed that PSA, MNV, and Gleason score were significant predictors of prognosis (P = 0.0126, 0.0148, and 0.0375, respectively). Multivariate analysis revealed that MNV and preoperative PSA were powerful independent predictors of prognosis (P = 0.0160 and P = 0.0147, respectively), but the Gleason score was not correlated with prognosis (P = 0.4120). For patients with PSA failure, PSA DT was significantly correlated with MNV (r = -0.597, P = 0.0099). When these patients were classified using median PSA DT at 6 months into two groups, MNV was significantly greater in PSA rapid-riser group than in the slow-riser group (P = 0.0008), but no differences were observed between these groups in PSA, the Gleason score, or cancer volume.

CONCLUSIONS

The findings of the present study suggest that MNV is a powerful predictor of PSA failure for patients with clinically organ-confined disease treated with radical prostatectomy. More importantly, they suggest that MNV can be a useful new parameter for prediction of tumor biology for patients with PSA failure after radical prostatectomy.

The new era of automated immunoassay

Use of immunoassays and other ligand-binding assays in clinical diagnosis has increased dramatically during the last several years. Despite impressive technical advances, "mass production" of these assays in a routine laboratory still presents many difficulties. This review of ligand-binding assay technology highlights some recent developments, emphasizing challenges and possible solutions for cost-effective patient care.

Relapse and cure rates of prostate cancer patients after radical prostatectomy and 5 years of follow-up

OBJECTIVES

We have compared the ability of an ultrasensitive prostate specific antigen assay and a regular PSA assay to identify relapse and cure rates of prostate cancer patients after radical prostatectomy, during a 5-year follow-up period.

DESIGN AND METHODS

We measured PSA by an ultrasensitive assay (detection limit 0.001 ng/mL) and a conventional PSA assay (detection limit 0.1 ng/mL) in serial serum samples obtained from 197 patients who have undergone radical prostatectomy.

RESULTS

Based on ultrasensitive PSA analysis, we have identified three groups of patients: 62% of patients did not show any significant changes in serum PSA; 15% of patients demonstrated slow PSA increases over time but none of the measurements exceeded 0.1 ng/mL within 4 years; and 23% of the patients had relatively significant increases of serum PSA and were classified as having 'fast relapse'. The vast majority of these patients were subsequently identified to have relapse by the regular PSA assay. The ultrasensitive PSA assay detected relapse by an average of eighteen months earlier than the conventional PSA method. Fast relapsing patients were associated with other prognostic indicators of the disease including pre-operative PSA, tumor volume, Gleason score, clinical stage, surgical margin positivity, periprostatic tissue involvement, capsular invasion and seminal vesicle invasion. The group with slowly rising PSA had prognosis which was between the patients in remission and fast relapsing patients.

CONCLUSIONS

The use of ultrasensitive PSA analysis for monitoring patients after radical prostatectomy provides earlier detection of relapse (by 18 months) and identifies three distinct groups of patients. Fast relapsing patients should be good candidates for early therapeutic interventions.

Efficacy and limitations of delayed/salvage radiation therapy after radical prostatectomy

OBJECTIVE

To assess the kinetics of prostate specific antigen (PSA) and the degree of PSA suppression, to better understand the efficacy and limitations of delayed/salvage radiation therapy after radical prostatectomy.

PATIENTS AND METHODS

The PSA doubling time was calculated in patients with biochemical failure after radical prostatectomy and in those who underwent delayed/salvage radiation therapy. Patients in whom PSA was undetectable by conventional assay after irradiation were followed using a hypersensitive PSA assay.

RESULTS

Of 125 patients who underwent radical prostatectomy for clinically resectable prostate cancer, 47 developed biochemical failure at a mean of 11.8 months after surgery; 38 of these patients underwent radiotherapy (36 for isolated biochemical failure and two for local progression with elevated PSA levels). The mean (sd) PSA doubling time after surgery was 14.6 (16.2) months (n=44) and after radiation therapy it was 13.3 (23.9) months (n=32). Eleven of 30 evaluable patients (37%) had a sustained PSA suppression lasting at least 12 months after radiotherapy. Only the time to biochemical failure after surgery approached statistical significance for predicting a durable response to radiotherapy (P=0.08). The mean nadir value of PSA in the 11 patients with at least 12 months of sustained PSA suppression was 0.032 ng/mL at 26.9 months.

CONCLUSIONS

The rapidity with which PSA levels double after surgery may provide a clinically significant indication of the nature of these recurrent tumours, which deserve the best possible attempt at cure. Slow-growing tumours with longer PSA doubling times may be better candidates for delayed/salvage radiation therapy. Larger studies involving more patients are needed to determine whether the PSA doubling time can define subgroups for which specific treatment strategies should be developed.

Measurement of prostate-specific antigen in detection of benign or malignant breast disease in women

Using a highly sensitive chemiluminescent enzyme immunoassay, we have evaluated the measurement of serum prostate-specific antigen (PSA) as a potential diagnostic test for differentiation between women with breast cancer and those with benign breast disease. In a controlled study consisting of 284 women with well-documented patient files and matched for age and long-term place of residence, serum samples collected from 90 women with histologically confirmed breast cancer, 94 women with benign breast disease and 100 controls were analysed. Serum total PSA levels in benign breast disease and cancer patients are not statistically different from those of healthy controls. Total PSA levels decrease with age in normal controls and breast cancer patients but not in those with benign breast disease. The total PSA concentration decreases after menopause in healthy women, though not in patients with breast cancer or benign breast disease. Total PSA bore no relation to the histological type or grade of the tumour or the disease stage of the breast cancer patients. In benign breast disease, all mastopathy patients had normal total PSA, whereas elevation of the values was observed in 7% of fibroadenoma patients. Our results show that serum total PSA cannot be used to distinguish between healthy women and/or women with breast cancer or benign breast disease.

Limited suppression of prostate-specific antigen after salvage radiotherapy for its isolated elevation after radical prostatectomy

OBJECTIVES

To investigate the clinical outcome and degree of prostate-specific antigen (PSA) suppression after salvage radiotherapy performed because of isolated PSA elevation after radical prostatectomy.

METHODS

We examined the outcomes of 32 patients who underwent radiotherapy after radical prostatectomy. Hypersensitive, as well as conventional, PSA assays were used to measure PSA levels after irradiation.

RESULTS

Of 125 patients who underwent radical prostatectomy for clinically resectable prostate cancer, 42 (33.6%) developed detectable PSA an average of 13.5 months postoperatively. Thirty-two patients underwent salvage radiotherapy. In 13 patients (40.6%), PSA became undetectable (less than 0.1 ng/mL) at a mean of 1.2 months. Two of these patients later developed detectable PSA within 1 2 months. Of 22 patients who had at least 12 months of follow-up, 8 had a durable PSA response. Of 13 patients who attained an undetectable PSA postoperatively and then showed a delayed progressive increase, 7 exhibited a durable response lasting for more than the 12 months after irradiation. By contrast, only 1 of 9 patients with persistently elevated postoperative PSA showed undetectable levels after irradiation. Frozen sera from the 8 patients with a durable response to irradiation were available to measure levels less than 0.1 ng/mL by hypersensitive assay. The mean value was 0.035 ng/mL at an average of 26.9 months after irradiation. Only 3 patients had levels less than 0.01 ng/mL.

CONCLUSIONS

Although radiotherapy may be beneficial in a small number of patients, many patients continue to have measurable levels of PSA (more than 0.01 ng/mL) after irradiation. Our results suggest that this treatment in its current form is inadequate to eradicate residual carcinoma.

Ultrasensitive assay of prostate-specific antigen for early detection of residual cancer after radical prostatectomy

OBJECTIVES

Perhaps the greatest value of PSA determination in the treatment of prostate cancer is in determining persistent disease after a radical prostatectomy. We investigated the ability of an ultrasensitive PSA assay to detect residual prostate cancer in men at risk for recurrence after a radical prostatectomy.

METHODS

Using the Immulite third-generation PSA assay (detection limit, less than 0.003 ng/mL), and the standard IMx PSA assay, we determined PSA levels in 205 serum samples serially obtained from 34 men after a radical prostatectomy. The average days from surgery to serum sampling was 430 (range, 63 to 1296). Patients were classified as having nonaggressive or aggressive cancers, based on clinicopathologic findings. A biochemical relapse was arbitrarily defined.

RESULTS

All 17 patients with nonaggressive cancers had PSA values of less than 0.02 ng/mL throughout the sampling period. Two of these patients (12%) had 2 or more consecutive PSA increases and were considered as a biochemical relapse. In contrast, 14 (82%) of 17 patients with aggressive cancers fit criteria of a biochemical relapse. All of the relapses were identified within 2 years after surgery. The IMx assay detected only 7 biochemical relapses during the same sampling period.

CONCLUSIONS

Using the Immulite PSA assay, relapse detection times may be shortened allowing for most serological recurrences to be detected within 2 years after a radical prostatectomy. Patients with aggressive cancers may require frequent postoperative PSA determinations with a highly sensitive PSA assay which would allow early intervention when treatments for relapse are effective.

Prostate-specific Antigen: Its Usefulness in Clinical Medicine

Prostate-specific antigen (PSA) was discovered about 20 years ago and over the last decade it has become the premier tumor marker for diagnosis, monitoring and prognosis of prostatic carcinoma. PSA is now considered to be the best tumor marker available in clinical medicine. It is the only tumor marker that has been approved by the Food and Drug Administration of the USA for mass screening: for the purpose of diagnosing early prostatic carcinoma. Among the newest developments in the field are the discovery of the molecular forms of PSA in serum, the development of ultrasensitive assays that allow better monitoring of patients after radical prostatectomy, and the discovery of non-prostatic PSA. Indeed, there are indications that PSA might be useful for the diagnosis and prognosis of breast cancer. The genomic structure of PSA and other human kallikrein genes and the regulation of their expression has recently been elucidated. Currently, the PSA promoter and enhancer are being investigated in connection with gene therapy in prostatic tissue. Efforts are now underway to supplement the clinical value of PSA measurements with additional prostatic markers, including human kallikrein 2 (hK2) and prostate-specific membrane antigen (PSMA).

Clinical implications of prostate‐specific antigen (PSA)

Prostate-specific antigen(PSA) is currently the tumour marker of choice for prostatic carcinoma. This article examines the current literature on the application of PSA for cancer detection (concentrating on values of PSA in the normal and 'grey' areas of 2.5-10 ng/ml), in staging of the disease and prediction of treatment response. These areas in particular have been refined by the use of PSA indices (PSA density, velocity, age ranges) and the article focuses on the recent studies analysing their standing in clinical practice.

Prostate-specific antigen and new related markers for prostate cancer

Although prostate-specific antigen (PSA), or human kallikrein 3, is the most valuable tool available for the diagnosis and management of prostate cancer, as currently used it is insufficiently sensitive and specific for early detection or staging of the malignancy. Many new concepts have been introduced in order to optimize the clinical use of PSA measurements, but each one has its own drawbacks. The molecular forms of PSA, especially the free PSA, seem to be useful for the detection of prostate cancer in men with PSA concentrations falling in the 4-10 microg/l range. New molecular techniques, such as reverse transcriptase polymerase chain reaction for the detection of minimal amounts of PSA messenger RNA and prostate-specific membrane antigen, offer new promise for the prognosis and possibly staging of prostate cancer. On the other hand, human kallikrein 2, a serine protease closely related to PSA that is also expressed predominantly in the prostate, may be a new adjuvant marker for prostate cancer. As for its biological functions, PSA can no longer be regarded as a specific prostate molecule associated mainly with semen liquefaction when it has a possible role as a prognostic indicator in female breast cancer. The biological role of PSA in normal tissues and tumors may be much more complex than previously thought and requires further investigation.

Human Kallikrein 2 (hK2) and prostate-specific antigen (PSA): two closely related, but distinct, kallikreins in the prostate

Recent studies on human kallikrein 2 (hK2) have revealed striking similarities and significant differences with the closely related kallikrein PSA. Both PSA and hK2 are primarily localized to the prostate and share close structural similarities. Although both kallikreins are produced by the same secretory epithelial cells in the prostate, hK2 is associated more with prostate tumors than PSA and is highly expressed in poorly differentiated cancer cells. The potent trypsin-like activity of hK2 contrasts with the weak chymotrypsin-like activity of PSA. The inactive precursor form of PSA, proPSA, is converted rapidly to active PSA by hK2, suggesting an important in vivo regulatory function by hK2 on PSA activity. The high homology between hK2 and PSA results in significant cross-reactivity to hK2 by polyclonal and some monoclonal antibodies to PSA. Future studies on both PSA and hK2 need to take into account this potential for cross-reactivity. Specific monoclonal antibodies to hK2 have now demonstrated that serum levels of hK2, like PSA, are correlated with prostate cancer. The production of hK2 protein in active protease form and specific monoclonal antibodies to the hK2 antigen will allow extensive future studies delineating the physiological and clinical utility of this new prostate antigen.