Histological chronic prostatitis and high-grade prostate intra-epithelial neoplasia do not influence urinary prostate cancer gene 3 score

Authors


Correspondence: Stefano De Luca, Division of Urology, Ospedale Gradenigo, C.so Regina Margherita 8, 10153, Torino, Italy.

e-mail: delucastefano@yahoo.it

Abstract

Study Type – Diagnostic (case series)

Level of Evidence 4

What's known on the subject? and What does the study add?

While the relationship between PCA3 score and clinical or histological prostatitis was quite proven even in small patient groups, conversely the relationship between PCA3 score and HG-PIN is still under debate.

We demonstrated in a large series (432 patients) that histologically documented chronic prostatitis and HG-PIN have similar PCA3 scores to patients with BPH and/or normal parenchyma at biopsy.

Objective

  • To determine whether histological chronic prostatitis and high-grade prostate intra-epithelial neoplasia (HG-PIN) influence the prostate cancer gene 3 (PCA3) score in Italian patients with an elevated prostate-specific antigen (PSA) level and a negative digital rectal examination (DRE) who were undergoing a first or repeat prostate biopsy.

Patients and Methods

  • A urinary PCA3 test was prospectively performed in 432 consecutive patients who were admitted to Gradenigo Hospital (Turin, Italy) between January and December 2011 and scheduled for first or repeat prostate biopsy as a result of an elevated PSA level and negative DRE.
  • A comparison of the PCA3 score and patients with a negative biopsy (normal parenchyma, benign prostatic hyperplasia, chronic prostatitis, HG-PIN) or positive biopsy was performed.

Results

  • PCA3 median (range) scores varied significantly (P < 0.001) in men with a negative vs positive biopsy: 33 (2–212) and 66 (5–324), respectively.
  • By contrast, men with chronic prostatitis and HG-PIN showed no significant difference with respect to PCA3 score compared to other negative biopsy patients.
  • No correlation was found between the number of positive cores for chronic prostatitis, HG-PIN and PCA3 score.
  • Of all patients with a positive biopsy, 23 (20%) of 114 men had a PCA3 score ≤35.
  • In total, 79 (40%) of 197 men with a negative biopsy (normal parenchyma and benign prostatic hyperplasia), 24 (37.5%) of 64 men with chronic prostatitis and 19 (39.6%) of 48 men with HG-PIN had a PCA3 score >35.

Conclusion

  • At this early stage of clinical evaluation, cancer specificity of the urinary PCA3 test appears to be maintained in the face of chronic prostatitis and HG-PIN.

Introduction

Prostate cancer gene 3 (PCA3), first described by Bussemakers et al. [1], is a non-coding, prostate-specific mRNA that is highly overexpressed in 95% of prostate cancer cells, with a median 66-fold up-regulation compared to adjacent non-neoplastic prostatic cells [2]. PCA3 represents the target in a molecular assay of urine for prostate cancer detection [3, 4]. An increased PCA3 score corresponds to an increased probability of a positive biopsy and its diagnostic value has been shown primarily in men with a previous negative biopsy and an elevated PSA level [5].

In the first published study on the measurement of PCA3 in urine obtained from patients with a suspicion of prostate cancer, up to 37% of the tested patients were diagnosed with ‘chronic prostatitis’ according to the final biopsy results [2]. Their median PCA3 score was no different to that in patients with a normal prostate histology and it was concluded that both types of patients could be grouped together as a unique population of non-cancerous patients for use as a comparison group when evaluating patients with cancer. Similar results were shown in other studies [6-9]. Some studies have shown that the PCA3 score rises in high-grade prostate intra-epithelial neoplasia (HG-PIN) [10], with this pathological feature being considered a precancerous condition.

The present study aimed to determine whether histological chronic prostatitis and HG-PIN influence the PCA3 score in Italian patients with an elevated PSA level and a negative DRE who were undergoing a first or repeat prostate biopsy.

Patients and Methods

A urinary PCA3 test was prospectively performed in patients who were admitted to Gradenigo Hospital (Turin, Italy) and scheduled for first or repeat prostate biopsy as a result of an elevated PSA level and a negative DRE.

In total, 432 consecutive patients were included between January and December 2011.

There were 61 (14%) patients who had a history of chronic prostatitis (pelvic and/or perineal pain or discomfort, dysuria, urinary frequency, ejaculatory symptoms).

The institutional review board approved the present study and all patients provided their informed consent to participate.

All PCA3 tests were carried out using the PROGENSA PCA3 assay (Gen Probe Inc., San Diego, CA, USA) in accordance with the manufacturer's instructions. Briefly, PCA3 and PSA mRNAs was extracted from exfoliated prostate cells in urine samples after DRE, and then amplified and finally hybridized using DNA probes tagged with a chemiluminescent substance. The hybridized number of PCA3 mRNA and PSA mRNA copies was counted with a luminometer and the ratio of the two (i.e. PCA3 score) was calculated as PCA3 mRNA/PSA mRNA × 1000.

Urine samples were considered as non-informative for prostate cells if <10 000 PSA mRNA transcripts were detected.

The PCA3 test was considered negative with a PCA3 score <35 (i.e. usual limit) and positive with a PCA3 score ≥35.

Men with atypical small acinar proliferation and/or a positive DRE were excluded.

At least 10–14 standardized peripheral zone biopsy cores were taken at first biopsy and 14–18 peripheral and transition zone biopsy cores were performed at repeat biopsy by experienced urologists. All specimens were evaluated by an experienced pathologist dedicated to uropathology.

Patients characteristics were tested using Fisher's exact test for categorical variables and Mann–Whitney and Kruskal–Wallis tests for continuous variables. P < 0.05 (two-sided) was considered statistically significant. The data were analyzed using SPSS, version 20 (IBM, Armonk, NY, USA).

Results

A total of 423 (97.9%) urine samples had adequate levels of PCA3 mRNA and PSA mRNA to enable calculation of the PCA3 score.

The characteristics of the study population with respect to the biopsy results are summarized in Table 1. The median (range) age was 68 (41–82) years. Median (range) PSA level, percentage free PSA and PCA3 score were 6.6 (2.5–48) ng/mL, 15% (3–37%) and 38 (2–324), respectively.

Table 1. Patient characteristics by biopsy results
CharacteristicValuePositive biopsy (N = 114; 26.9%)Normal parenchyma and BPH (N = 197; 46.6%)Chronic prostatitis (N = 64; 15.2%)HG-PIN (N = 48; 11.3%)Comparison of the three groups with a negative biopsy (P)
Age (years), median (range)68 (41–82)70 (46–82)68 (42–80)67 (41–78)69 (44–81)0.81
Cancer familiarity (positive), n/N (%)22/423 (5.2)18 (4.2)1 (0.02)2 (0.04)1 (0.02)0.27
First biopsy, n/N (%)70/423 (16.5)24/70 (34.3)39/70 (55.7)7/70 (10)10/70 (14.2)
Repeat biopsy, n/N (%)353/423 (83.5)90/353 (25.5)158/353 (44.7)57/353 (16.1)38/353 (10.7)
Serum total PSA level (ng/mL), median (range)6.6 (2.5–48)8.3 (3.6–48)6.4 (2.5–39)7.6 (2.7–44)7.9 (2.6–41)0.05
Percentage free PSA, median (range)15 (3–37)13.4 (3–32)16 (3–37)17.3 (5–29)14.2 (5–30)0.08
PCA3 score, median (range)38 (2–324)66 (5–324)33 (2–212)31 (2–132)29 (3–98)0.94

In the first biopsy group, 24 (34.3%) of 70 patients had cancer. In the repeat biopsy group, 90 (25.5%) of 353 men had a positive biopsy.

In total, 309 (73%) patients had a negative biopsy. Of these, 197 (46.6%) had normal parenchyma and BPH, 64 (15.1%) had a diagnosis of chronic prostatitis and 48 (11.3%) had a diagnosis of HG-PIN (multifocal in five patients).

Patients with either a positive biopsy or chronic prostatitis or HG-PIN had a statistically significantly higher total PSA level compared to men with normal parenchyma and BPH (Table 1).

The diagnostic performance of the PCA3 test in the first biopsy and repeat biopsy groups is shown in Table 2.

Table 2. Diagnostic performance of the prostate cancer gene 3 test in first and repeat biopsy groups
VariableFirst biopsyRepeat biopsy
Sensitivity (%)80.877.3
Specificity (%)28.366.8
Negative predictive value (%)78.187.8
Positive predictive value (%)36.654.2

PCA3 median (range) scores varied significantly (P < 0.001) between men with a negative and positive biopsy: 33 (2–212) and 66 (5–324), respectively.

By contrast, men with chronic prostatitis and HG-PIN had no significant difference with respect to PCA3 score compared to normal parenchyma and BPH patients (31 and 29, respectively, vs 33; P = 0.94). Plots of the PCA3 score in chronic prostatitis, normal parenchyma/BPH and HG-PIN patients are shown in Fig. 1.

Figure 1.

Plots of prostate cancer gene 3 (PCA3) score in chronic prostatitis, normal parenchyma/BPH and high-grade prostate intra-epithelial neoplasia (HG-PIN) patients.

No correlation was found between the number of positive cores for chronic prostatitis, precancerous lesions and the PCA3 score. There were 23 (20%) of 114 patients with a positive biopsy who had a PCA3 score ≤35. In total, 79 (40%) of 197 men with a negative biopsy (normal parenchyma and/or BPH), 24 (37.5%) of 64 men with chronic prostatitis and 19 (39.6%) of 48 men with HG-PIN had a PCA3 score >35 (multifocal in one out of five patients).

In 11% of BPH patients and 13% of chronic prostatitis patients had PCA3 levels >100.

No men with HG-PIN had a PCA3 score >100.

A history of chronic prostatitis (pelvic and/or perineal pain or discomfort, dysuria, urinary frequency, ejaculatory symptoms) had no impact on the final biopsy result (negative vs positive vs phlogosis).

No correlation was found between PCA3 and PSA, PCA3 and percentage free PSA in the three groups of patients.

Discussion

At present, up to two-thirds of patients who undergo a prostate biopsy will have a negative histology because the need to biopsy is based on serum PSA assessment, which comprises a sensitive but mostly unspecific test (i.e. PSA levels increase in clinical situations other than prostate cancer) [11]. Benign changes ranging from atrophy and inflammation to a preneoplastic lesion such as HG-PIN are common findings on prostate needle core biopsies [12, 13].

Mild or moderate inflammation may be sufficient to alter cellular integrity and cause the leakage of PSA into the serum. Along with direct trauma (e.g. biopsy, cystoscopy), chronic prostatitis is the most common cause (≈ 10% of all men suffer from the symptoms of prostatitis syndrome) of a sudden, marked imcrease in serum PSA levels [14, 15].

Inflammation is often histologically apparent in the examination of prostate specimens from older men. The cause of chronic prostatic inflammation, as well as its putative role in carcinogenesis, remains unclear [16]. Previous studies have found both positive [17] and negative [18] associations between inflammation and the incidence of prostate cancer. The positive correlation between inflammation and circulating PSA levels [19] strengthens the biological plausibility of a link between inflammation and cancer, although it also confounds studies aiming to determine whether an association exists between the two [13]. In patients with a negative biopsy performed as a result of an elevated PSA level, either undetected cancer or subclinical prostatitis (if histological evidence of inflammation is present) may serve as plausible explanations for the high PSA level.

The improved characterization of the types of inflammation that indicate a benign process vs an early-stage cancer remains a challenge. HG-PIN is the only accepted precursor of prostatic adenocarcinoma, according to numerous studies conducted in animal models and man [20-22]. It is characterized by progressive abnormalities of phenotype and genotype that are intermediate between a benign prostatic epithelium and cancer. The only method of detection of PIN is biopsy because it does not significantly increase serum PSA levels and cannot be detected by ultrasonography.

The mean (range) incidence of PIN in biopsies is 9% (4–16%) [20]. The clinical importance of HG-PIN is its high predictive value as a marker for adenocarcinoma, and its identification warrants repeat biopsy for concurrent or subsequent carcinoma, especially when multifocal or observed in association with small acinar proliferation [21]. Carcinoma develops in most patients with HG-PIN within 10 years [22].

To reduce unnecessary biopsies and to improve upon PSA specificity, past research has primarily investigated PSA derivates [23, 24], such as percentage free PSA, PSA velocity or density. Most of these derivates are of some diagnostic use, although none are sufficiently effective to definitively solve the problem.

The PCA3 assay test was launched commercially to select candidates for prostate biopsy [1, 25]. At the cellular level, PCA3 specificity for cancer is very good because of the gross overexpression of the gene by cancer cells. PCA3 is overexpressed in up to 95% of all prostate cancers tested and is expressed 60- to 100-fold less in non-cancerous tissues compared to cancerous tissues [1, 25-27]. The PCA3 test requires collection of the first 20–30 mL of voided urine after DRE; without DRE, the test provides valid results in only ≈80% of cases, whereas DRE increases this yield to more than 98%.

We have shown previously that the test performed very differently in patients who had no previous biopsies and those who had one or more previous biopsies [28]. In the latter patients, the PCA3 receiver–operating characteristic curve showed significantly better results; conversely, the PCA3 test performed poorly in the first biopsy group.

In an prospective study aiming to evaluate the effect of chronic prostatitis on PCA3 score, the urinary marker was found to be negative (less than the usual limit of 35) in all negative biopsy patients, suggesting that the PCA3 test can be used as a valuable tool in patients with raised PSA levels and a suspicion of chronic prostatitis or BPH to distinguish those patients who will benefit from prostate biopsy [9]. According to Vlaeminck Guillen et al. [9], the increased PCA3 score in these patients is unlikely to be related to chronic prostatitis or BPH and represents an additional reason for performing prostate biopsy.

On the other hand, a prospective study showed that the PCA3 score was significantly higher in HG-PIN compared to a cancer-negative group [10]. A relevant finding was that men with HG-PIN show PCA3 scores comparable to those in men with cancer. According to Ferro et al. [10], this finding probably reflects early molecular changes in a presumptive premalignant lesion [29, 30]. Such data are in agreement with previous studies showing that the discriminative performance of the PCA3 score is lower between HG-PIN and prostate cancer [5, 31].

By contrast, we have shown that histologically documented chronic prostatitis and HG-PIN (even in the very few multifocal groups) have PCA3 scores similar to those in patients with BPH and/or normal parenchyma at biopsy. Otherwise, we observe a positive PCA3 score >35 in 40% of men with a negative biopsy (normal parenchyma and/or BPH), in 37.5% of men with chronic prostatitis and in 39.6% of men with HG-PIN.

The frequency of PCA3 false positive results in chronic prostatitis and HG-PIN is comparable to a similar frequency in patients with a negative biopsy.

A better specificity would be expected for scores >100, although this was not the case. Notably, PCA3 levels >100 were found in 11% of BPH patients and in 13% of chronic prostatitis patients. In these cases, it remains to be determined whether the increased PCA3 score is not the result of an unidentified associated prostate cancer.

Unexpectedly, no men with HG-PIN had a PCA3 score >100 in the present series.

In a study by Robool et al. [32], the positive predicting value for PCA3 >100 was only 52%, which was unexpected, and, although there are no explanations for this, the results were confirmed in our previous study [28].

At this early stage of clinical evaluation, the cancer specificity of the urinary PCA3 test in Italian patients with an elevated PSA level and a negative DRE who are undergoing a first or repeat prostate biopsy appears to be maintained in the face of the major cause of a non-cancerous elevated PSA level (i.e. chronic prostatitis) and also in the face of HG-PIN, the only accepted precursor of prostatic adenocarcinoma.

Conflict of Interest

The authors declare that there are no conflicts of interest.

Abbreviations
HG-PIN

high-grade prostate intra-epithelial neoplasia

PCA3

prostate cancer gene 3

Ancillary