Prostate-specific antigen, or PSA , is a glycoprotein produced exclusively by the secretory cells lining the prostate gland to maintain semen fluidity so that sperm can swim. While in healthy patients, with normal cellular function, PSA is primarily confined to the gland itself, in patients with PCa, the disorganization of malignant cells enables the PSA to travel outside the lumen and into the bloodstream more easily. Thus, concentration of PSA in the blood can be used as a marker for PCa. The utility of PSA as a marker for PCa was first observed in men already known to have prostate cancer, as a method to monitor the disease [10]. PSA levels were shown to increase with advancing clinical stage, and were found to be useful in detecting biochemical recurrence (BCR) following definitive therapy [11]. PSA is also commonly used in men without a diagnosis of PCa, as an early screening method. An abnormal PSA value may be associated with finding PCa upon biopsy, this chance has been displayed to be as high as 50% in patients with PSA values ≥10 ng/ml [11–13]. When used along with digital rectal exam (DRE) and ultrasounds , PSA can greatly increase the ability for early detection of PCa, while it is still low risk and manageable [7, 12].

The use of PSA as a screening tool was a breakthrough that increased early detection of PCa, lowered the rate at which patients were diagnosed with metastatic carcinoma, and greatly reduced the death rate associated with PCa [4, 6]. However, PSA has been displayed to have variable reliability from patient to patient with respect to diagnosing PCa due a large number of factors that can cause fluctuation, and as a result the clinical utility of PSA is in this setting limited [14]. PSA levels have been found to differ based on race and to increase steadily with age, such that different reference ranges can be considered normal for men of different races and age brackets (Table 17.1) [15, 16]. Additionally, bacterial prostatitis, asymptomatic prostate inflammation, urinary retention, recent surgical procedures to the prostate, and even DREs can artificially increase PSA levels in men without PCa [17–21]. In contrast, obesity and even the use of common medications such as 5-α reductase inhibitors (5-ARs), NSAIDS, thiazides, and statins have been found to lower serum PSA levels [22–29]. This lack of specificity (a given PSA value has to PCa) is cause for concern for urologists when treating patients both with and without diagnosed PCa.

Following a positive biopsy, pretreatment PSA levels are used in conjunction with other tests such as imaging and DRE to stratify risk among pathologic groups. In fact, PSA is a decisive factor in many risk grading systems, such as the National Comprehensive Cancer Network guidelines. These predictions guide physicians and patients in choosing appropriate treatment options upon diagnosis as well in managing care further down the line. Thus, PSA variability , particularly in patients with low and intermediate pathological risk groups, can lead to both under and over treatment. Due to earlier and higher frequency screening, and the subsequent increased detection of low risk, very low risk, and indolent PCa, overtreatment is becoming a larger problem. An elevated PSA value can lead to aggressive treatment with invasive therapy for disease that may have been better managed with Active Surveillance [4]. Following definitive therapy such as radiation therapy and radical prostatectomy, PSA is monitored regularly for evidence of biochemical recurrence . While PSA variability is of less concern post-prostatectomy due to the removal of the gland itself, there is evidence for a “bounce” phenomena that can occur following radiation therapy, in which there is a transient rise, or bounce, in PSA that can last 12–18 months following the initial drop in PSA post radiation therapy [30]. Many efforts have been made by organizations such as American Society for Radiation Oncology (ASTRO) consensus panel to define and establish standards, on how PSA monitoring for biochemical recurrence should be done and how the results should be interpreted [14, 31–33].

In some cases more specific analyses of different PSA Isoforms and derivatives can improve upon the lack of specificity a total serum PSA (tPSA) has in diagnosing PCa, and be used to better stratify patients with similar PSA values into risk groups. One of the more widely used techniques involves comparing the free PSA levels to the total PSA levels in the blood. PSA can exist in the blood in both bound and unbound, free forms. In healthy men with benign conditions, PSA exists in the blood more predominantly in the free form. Therefore, measuring the ratio of free PSA (fPSA) to tPSA can help determine whether an elevated PSA is due to PCa or a benign condition. This is particularly useful in men with intermediate PSA levels between 4 and 10 ng/mL, for which PSA is a poor predictor of biopsy outcome. The use of a 25% cutoff for % fPSA was noted to have a 95% sensitivity and 20% specificity to PCa, providing an advantage over tPSA alone [34]. Other techniques such as PSA velocity or PSA doubling time analyze the rate at which PSA levels are increasing which is a better indicator of the cancer’s aggressiveness and progression [35]. These measures are useful in monitoring men already diagnosed with PCa, however, they have proven to increase the number of unnecessary biopsies when used for screening [36]. While these methods can increase the ability to diagnose and monitor PCa, more comprehensive assays have been developed.

As discussed, serum PSA analysis is a routine screening procedure for patients without an existing diagnosis of PCA. Therefore, the variability of PSA values can lead to both false positives and false negatives regarding PCa diagnosis, which has sparked a debate about under and over diagnosing PCA [7, 8]. Of particular concern is the frequency with which elevated PSA values lead to prostate biopsy in asymptomatic men and exposing them to unnecessary risk [7, 8]. This is particularly common for men with low serum levels (2.5–4.0 ng/ml), as using this as a cutoff results in a false-positive rate of roughly 80% [37]. Even in patients with intermediate serum PSA levels (4.00–10.00 ng/ml), the likelihood of a diagnosis of PCa upon biopsy is as low as 22–27% [11, 12]. Of further concern is that men with false positives are more likely to have subsequent testing and biopsies, exposing them to further risk [38]. Thus, PSA driven management of care in men without a diagnosis of PCa is highly controversial, to the point that the US Preventative Service Task Force recommended against routine PSA screening in men on the grounds that the harm done by overtreatment outweighs the benefit of early detection on the whole [39]. These issues along with the proven utility of PSA screening in decreasing PCa morbidity and mortality, suggest a need for improved biomarkers with both higher specificity and sensitivity.

The Prostate Cancer Prevention Trial Risk Calculator (PCPTRC) from the University of Texas Health Science Center and Department of Urology is a risk stratification tool meant to aid in the decision of whether or not to proceed with a biopsy. It was originally developed using data from the PCa Prevention Trial in 2006, which followed 5519 men with no previous diagnosis of PCa and a PSA of 3.0 ng/mL or below for seven years with an annual DRE and PSA [35]. After 7 years, even if an abnormal DRE or PSA prompted one already, all men were recommended to undergo a prostate biopsy. The findings of the trial were used to generate an online calculator that uses ethnicity, age, PSA level, family history of PCa, DRE, and prior biopsy results to estimate a preliminary risk assessment for PCa prior to a prostate biopsy. The calculator has since been updated to the PCPTRC 2.0 through the incorporation of more patient data and the addition of new predictive capabilities regarding low grade versus high grade disease. The main addition to the PCPTRC 2.0 is incorporation of % free PSA as a risk stratification measure. The addition of % free PSA significantly improved the ability to predictively differentiate the risk of high-grade cancer versus benign disease, but did not improve the ability to differentiate between low-grade and high-grade cancer or low-grade cancer and benign disease [36].

The calculator is recommended for use on patients that meet the criteria of 55 years of age or older, no previous PCa diagnosis, and a DRE and/or PSA from within the past year. Additionally, the calculator is limited by the demographics of patients studied in the PCPT. The majority of patients were Caucasian males thus potentially reducing its accuracy for other ethnicities. Furthermore, approximately 80% of the patients in the PCPT had a biopsy of six cores performed. For patients whose biopsies included more than six cores, the potential for detection of PCa can increase. Lastly, the inclusion of % free PSA in the PCPTRC 2.0 came from serum measurements in a separate cohort of patients and thus the results come from a mathematical merging of the two cohorts [36]. Overall, while the PCPTRC 2.0 provides physicians with a calculated assessment of an individual patient’s risk for PCa, it is not a stand-alone prognostic tool and must be considered in conjunction with other clinically relevant information (Fig. 17.1).

The Prostate Health Index (PHI) from Beckman Coulter, Inc. is a newer blood-based assay recently approved by the FDA for men of age 50 years or older with a PSA between 4 and 10 ng/mL and a negative DRE. It helps to distinguish non-cancerous conditions such as BPH or prostatitis from PCa. PHI utilizes an algorithm which incorporates free PSA, total PSA, and [−2] proPSA, an isoform of free PSA, to generate a PHI score. In addition, [−2]proPSA accounts for drastically higher proportions of the free PSA found in serum of men with PCa than that of men with benign conditions and as such, it has been found to be the most PCa-specific PSA isoform in cancerous tissue samples [40, 41]. Using the PHI score allows physicians to achieve better sensitivity as well as specificity in diagnosing PCa than any of its three components alone [42–44]. Using PHI in clinical practice can help patients with a lower risk of cancer avoid an unnecessary biopsy and respective side effects and complications, while also limiting the number of high grade tumors that are missed. As a result, it is the only multi-faceted blood assay incorporated into the National Comprehensive Cancer Network protocol for early detection of PCa.

The increased PCa specificity of the PHI score relative to standard PSA measurements has potential implications beyond PCa screening as well. In Active Surveillance patients, PHI has been shown to predict progression of disease and up-staging of Gleason score on surveillance biopsies [45]. An additional study has found preliminary evidence for [−2]proPSA to have a predictive value in the rate of metastatic versus non-metastatic progression in men with biochemical recurrence post-radical prostatectomy [46]. However, the actual benefit of PHI in these realms is unclear and there is a need for further evidence before PHI can be considered for use in patients already diagnosed with prostate cancer. Additionally, as with many of the diagnostic tools currently available, the PHI score is not a stand-alone prognosis indicator and must be considered along with patient history amongst other factors.

The PROGENSA^® PCA3 Assay by Hologic, Inc. is a tool utilized by physicians and patients in deciding whether or not to proceed with a prostate biopsy. This assay, analyzes the expression of the DD3/PCa Gene 3 (PCA3) in cells obtained in urine sample provided by a patient following a DRE. The value of the PROGENSA^® PCA3 is that PCA3 expression is not only prostate specific, but is specific to PCa cells [47]. PCA3 is disproportionally expressed in cancerous tissue compared to that of benign tissue, and expression levels are independent of prostate volume, serum prostate specific antigen level and the number of prior biopsies [48, 49]. Hessels et al. reported the upregulation of PCA3 in PCa cells as high as 66-fold in over 95% of PCa cells, allowing for precise differentiation between cancerous and benign cells, and that 67% of men positive for PCA3 upregulation were positive for PCa upon Biopsy [50]. Compared to tPSA, PCA3 analysis has a higher specificity, positive predictive value, and negative predictive value regarding biopsy outcome [51].

In addition to PCa detection, there is preliminary evidence that PCA3 analysis can provide information on the potential progression or aggressiveness of disease. PCA3 scores have been displayed to predict tumor volume and extra-capsular extension in men undergoing radical prostatectomy [52, 53]. Lin et al. 2013 also demonstrated the utility of PCA3 analysis in stratifying risk in men with similar Gleason scores and tumor volume in an active surveillance cohort [54]. High PCA3 scores are also associated with increased Prostate Imaging Reporting and Data System (PI-RADS) grade on multi-parametric MRIs and increased Gleason scores on fusion biopsy [55].

The ability of PCA3 to differentiate benign prostatic conditions from PCa (specificity), makes this test useful for patients considering both initial and repeat biopsy. Use of the test could eliminate unnecessary biopsy in patients with abnormal PSA and/or DRE results and family history of PCa as well as identify PCa early in patients with normal PSAs whom otherwise may not be considered at risk. Additionally, the ability to differentiate between intermediate and high risk as well as indolent and low risk disease makes the test useful in deciding between definitive therapy and active surveillance. Thus, using PCA3 analysis can help to fill in the gaps left by PSA and Gleason score, and help patients and doctors more confidently decide on a course of treatment. A major limitation of the PCA3 analysis is the lack of long-term data. Its effectiveness has not been studied in patients more than 3 months prior to biopsy, or beyond 7 years post-biopsy. Additionally, there is insufficient information regarding the utility and validity of the PCA3 assay in patients undergoing androgen deprivation therapy, or in patients taking known PSA altering medication such as 5-ARIs. Furthermore, similar to many tools such as PSA, Gleason Score, or staging, PCA3 cannot be used on its own to diagnose or guide treatment for PCa. It is meant to complement existing information for a better informed decision on both the physician and patient’s behalf.

The 4Kscore^® Test from OPKO Lab is an algorithm that incorporates a panel of four biomarkers in the kallikrein protein family as well as clinical information including DRE results, family history, and age to predict the risk of aggressive PCa. The four components of the biomarker panel are the free PSA, total PSA, intact PSA (iPSA), and human kallikrein peptide 2 (hK2) . As previously discussed, analysis of both free PSA and intact PSA help to differentiate between benign and malignant prostatic disease, but it is the analysis of hK2 that really sets the 4Kscore apart from other assays, which focus only on PSA and its isoforms. HK2 is similar to PSA (hK3), in that it is prostate-specific and found in many different isoforms. However, this protein differs from PSA in that it has an exponentially higher enzymatic activity, is present at much lower levels in serum, is more highly associated with PCa, and most importantly its expression increases as PCa cells become more poorly differentiated [56, 57]. This makes the 4Kscore extremely effective as a predictor of high grade disease.

The predictive ability of the four kallikrein panel is highly tested in a variety of settings, and as such there is a great deal of information regarding its utility in PCa screening. The assay has been shown to significantly enhance discrimination between benign and malignant disease relative to PSA and other clinical information [58, 59]. There is also evidence that use of the four kallikrein panel in men with a previous negative biopsy and elevated PSA can better predict the outcome of repeat biopsy relative to PSA and DRE alone [60]. It has also been shown to have greater predictive ability for high grade disease in both biopsy and prostatectomy specimens [61, 62]. Additionally, longitudinal studies of the four kallikrein panel have displayed predictive ability for the risk of metastasis [59]. The ability of the 4Kscore to provide accurate predictions of such meaningful outcomes has large implications for its clinical utility.

The assay is generated using a blood sample in conjunction with relevant clinical information to generate a percent risk of aggressive PCa (Gleason score ≥ 7) on a continuous scale from <1% to >95%. A 4Kscore result less than 7.5% indicates low risk, between 7.5% and 19% is intermediate risk, and equal to or greater than 20% is considered high risk. Not only does this percent risk indicate a patient’s likelihood of having an aggressive form of PCa, but also the patient’s risk of distant PCa metastasis up to 20 years after the score is generated [63]. By providing the patient and physician with quantifiable information, use of the 4Kscore in concert with other measures can help tailor decision making to the individual patient with respect to age and quality of life. Estimations based on a United States based prospective clinical trial suggest that using the 4Kscore as a deciding factor on whether to proceed with biopsy could eliminate 36% of unnecessary biopsies while delaying diagnosis of significant tumors in only 1.7% of patients [63].

While the 4Kscore Test^® shows significant improvements in regards to stratification of risk groups to reduce overdiagnosis and overtreatment, there are limitations to its use and application. The 4Kscore Test^® excludes patients taking 5-ARI therapy or undergoing any invasive procedure known to influence PSA (i.e., TURP, prostate biopsy, BPH treatment, etc.) within the previous 6 months. Additionally, the blood sample must be taken four or more days after a DRE. Lastly, this assay cannot be used on patients with a prior diagnosis of PCa. Overall, the 4Kscore^® Test has made the most significant strides in more accurate risk stratification than more established assays such as PCA3, PHI, and PSA.

Confirm MDx (MDxHealth ) is an epigenetic assay available for men with a prior negative biopsy and elevated PSA or abnormal DRE that predicts the likelihood of negative repeat biopsy. The test measures methylation-specific epigenetic signature of the GSTP1, APC, and RASSF1 genes in cancer-negative biopsy core specimens. Methylation of these genes is highly associated with carcinogenesis and tumor analyses have displayed methylated GSTP1, APC, and RASSF1 to be present in a large portion PCa tumor cells [64, 65]. As a result, methylation ratios of these genes can be used as independent epigenetic markers for PCa [66]. Thus the analysis of these three methylation markers allows Confirm MDx to differentiate between false negatives and benign biopsies.

The MATLOCK study , which blindly tested archived biopsy specimens found that Confirm MDx correctly identified 68% of cancer missed on the previous biopsy and correctly identified 64% of patients who did not need a repeat biopsy [67]. Additionally, the negative predictive value (NPV) for Confirm MDx following the first negative biopsy was 90%, which was significantly better than the 65–75% NPV from histopathology alone [67]. The sensitivity, specificity and NPV of Confirm MDx have been shown in additional studies, which have confirmed the test to be the best independent predictor of repeat biopsies [65, 68].

The ability of Confirm MDx to prevent unnecessary repeat biopsies in men considered to be otherwise at risk for PCa has been shown to have a high degree of clinical utility. Roughly 40% of patients with a negative biopsy undergo a repeat biopsy, of which only 15% are positive for carcinoma, resulting in unnecessary costs and risk [13]. Confirm MDx helps reduce patient anxiety, complications and unnecessary health care expenses by ruling out non-cancer patients from undergoing another repeat biopsy or screening procedure. In clinical utility studies utilizing Confirm MDx, this number was reduced to only 4% for Confirm-negative men who were considered at risk based on traditional risk factors, demonstrating a ten-fold decrease in unnecessary procedures. In addition, of those who underwent repeat biopsy despite being Confirm-negative, none were diagnosed with PCa [69].

Proper implementation of increasingly specific biomarkers such as the PCA3 and [−2]proPSA in addition to more comprehensive assays which make use of multiple biomarkers and risk factors such as the PCPTRC, PHI, and 4 K Score, will help physicians and patients gain a more accurate understanding of their disease and the associated risk. In doing so, unnecessary procedures can be avoided without compromising detection and more effective treatment, that will provide improved long term outcomes. However, it is important to note that while these assays show potential through improved specificity in relation to PCa itself, they still lack specificity in relation to the individual patient being treated. Thus, there is room for improvement. Recent advances in the field of genetics and bioinformatics have led to the development of gene based assays , which can provide patient specific analysis of PCa specific risk.

Table 17.2 summarizes the different non-genomic biomarker assays used by physicians and patients to help determine whether or not to proceed with a biopsy.

The purpose of staging PCa is to determine how far the cancer has spread to facilitate decisions made by physicians regarding potential treatment options. TNM staging looks at three different aspects of the cancer- primary tumor (T), pelvic or regional lymph nodes (N), and distant metastasis (M). Some forms of treatment may not be realistic options for patients based on whether or not the cancer has remained confined to the prostate. Clinical TNM staging uses a compilation of information including DREs, biopsies, imaging studies, and lab tests to estimate the extent of disease progression in the absence of more definitive histopathology information. Pathological TNM staging is done following surgery on the prostate where a significant tissue sample is available for analysis. Based on the specimen’s pathology and surgical findings, clinical staging may be adjusted to better reflect the predicted progression of disease. However, staging is based almost completely on the anatomy of the cancer and while it still plays a crucial role as a prognostic tool, it cannot give a complete picture of PCa characteristics. TNM staging is still being developed to incorporate underlying biological information that has become available in more recent years.

A Gleason score (GS) is obtained by examining the differentiation of cells in tissue samples taken from the prostate during a biopsy, or in analysis of the gland as a whole following prostatectomy. When cells divide, the cytosolic fluid and cell contents are usually distributed evenly and certain genes are regulated to determine a cell’s specific function. Cancerous cells grow and divide rapidly without control resulting in uneven cytosolic distribution and inability to properly differentiate into their respective cell types. This often results in errors in cell replication and division, which further propagates the lack of growth control and differentiation. These characteristics can be visualized in the laboratory by sectioning and staining tissue samples for observation under the microscope (Fig. 17.2). Whether the samples are taken during a biopsy or prostatectomy, the degree of cell differentiation can be observed in order to determine the disease progression. The total GS is the sum of both the primary and secondary scores, which correspond to the most and second most common level of cell differentiation. Cells that appear well-differentiated are given a lower GS, which is most frequently associated with less aggressive cancers. The opposite holds true for poorly differentiated cells. These are assigned a higher GS indicating the likelihood of a more aggressive PCa. As displayed in Fig. 17.1, scores range from 1 to 5, however only cancer is only diagnosed when the total GS is ≥6. High risk GS is associated with more rapid disease progression, increased chance of extraprostatic extension following prostatectomy, and an increased risk of metastasis and PCa related death [70, 71]. Thus, GS is an important factor in determining treatment at diagnosis, as well as in patients with advanced disease.

While a GS provides important information regarding a patient’s disease, it only gives a snapshot of current disease progression. Gleason score is not an independent predictor of pathology, stage, or biochemical recurrence surgical following prostatectomy, and thus limited in its ability to direct treatment. The GS obtained at prostate biopsy is limited by sampling error. Unlike a prostatectomy specimen, which allows for exact pathological diagnosis of GS, biopsy specimens only provide a small random sample of tissue that may not be completely representative of the disease state, which can lead to miss-diagnoses. Although the concordance rate between biopsy specimens and prostatectomy specimens has increased over the past 20 years as a result of improved sampling methods, under-grading and over-grading via biopsy has been known to occur in as high as 26% and 5% of cases respectively [72–74]. Thus, while GS is useful in guiding treatment for patients, it should be used in combination with other measures such as PSA levels and clinical staging to give a more accurate picture of a patients disease.

The Partin Table is a risk stratification tool created by physicians treating PCa at the Johns Hopkins Brady Urologic Institute. Data from thousands of patients treated at the Brady Urologic Institute over many years have been accumulated and analyzed to design a table that predicts the likelihood of organ confined disease. This makes the Partin tables extremely valuable in determining the potential for radical prostatectomy to have a curative outcome. The Partin Table utilizes pre-treatment PSA, Gleason score , and clinical stage determined via DRE to predict the percent chance of organ confined disease, extracapsular extension (ECE), seminal vesicle invasion, and lymph node involvement. It has been updated over the years to incorporate the transforming demographic of the patient population following implementation of PSA screening as well as slight modifications in the Gleason scoring system. Some of these updates include evidence that changes the approach to the treatment of Gleason 8 patients who were previously thought not to benefit from radical prostatectomies due to the likelihood that their cancer had spread beyond. That is no longer the case. In fact, there is evidence that Gleason 8 patients are more similar in all postsurgical pathological outcomes to Gleason 4 + 3 (Gleason 7) patients than those with Gleason 9 or above, and thus have positive outcomes for disease management following radical prostatectomy [75]. Another use of the Partin tables is determining whether or not a lymphadenectomy is called for at the time of radical prostatectomy.

The Partin Table is a useful tool for physicians and patients to consult when deciding a treatment plan, especially to choose between surgical intervention versus other forms of treatment such as hormone therapy, chemotherapy, and radiation. However, there are limitations to the Partin Table including the inability to predict side-specific ECE. This could help physicians decide the necessary extent of prostate surgery such as nerve-sparing or unilateral prostatectomies, which may increase the likelihood of normal function following surgery. While there are other tools available that can predict side-specific ECE, the Partin Table does not stand alone in this regard.

Another tool developed by urologists at the Johns Hopkins Brady Urologic Institute is the Han Table. While the Han Table uses the same pre-treatment factors as the Partin Table (PSA level, Gleason score, and clinical stage), the Han Table is designed to predict the likelihood of biochemical recurrence following a radical prostatectomy at 3, 5, 7, and 10 years [75]. Additionally, the Han Table has two different models based on the available information. The preoperative model is used when a patient is considering a radical prostatectomy to determine the probability of biochemical recurrence following surgery if they elect that procedure. This model utilizes the PSA level, Gleason score, and clinical stage determined by DRE. The postoperative model incorporates the pathological stage in place of the clinical stage and surgical Gleason score in place of the Gleason score obtained during a biopsy, both of which can only be determined following surgery and are more representative of the disease state [75]. Thus, the Han Table can be a helpful tool in setting a surveillance plan for PCa management post-surgery, as well as for deciding on an initial treatment option. If the chances of biochemical recurrence following surgery are high, physicians will often recommend against this course of action to avoid side effects of a most likely ineffective treatment. Lastly, the Han Table was designed to be used in conjunction with the Partin Table, such that the predicted spread of a patient’s PCa could be used to determine whether or not surgery is a realistic option.