Pre-Surgical Biomarker Performance in the Detection of Gleason Upgrading in Prostate Cancer

Abstract

Background

Gleason Score (GS) upgrading is generally considered a trigger for exit to definitive treatment during active surveillance (AS). Predicting the potential for GS upgrading would be of value in assessing AS eligibility.

Methods

We assessed the performance of biomarkers in pre-surgical specimens of expressed prostatic secretion (EPS) in this setting.

Results

Although EPS volume, total recovered RNA, and RNA expression biomarkers (TMPRSS2: ERG, PCA3, PSA) have been successful in both biopsy outcome prediction, and in the prediction of upstaging in active surveillance eligible patients, they were unable to predict upgrading in patients eligible for active surveillance under NCCN guidelines.

Conclusions

These biomarkers do not improve the prediction of upgrading over indications from standard clinical parameters.

Impact

Additional biomarkers will be needed in this area.

Introduction

Current practice during AS is to monitor low risk patients by repeating biopsies periodically. Patients with an initial biopsy GS of 6 are offered definitive treatment if a repeat biopsy during surveillance yields a GS ≥ 7. This suggests that the cancer may have progressed during the interval from the previous biopsy. Even so, a sizable proportion of GS 7 patients may have been misclassified GS 6 due to sampling error on low volume tumors (1, 2). For this reason, a non-invasive test that could detect this relatively subtle change in Gleason sum would be of value.

Results with post-DRE urine (3, 4), have consistently mirrored those with (EPS) (5, 6), suggesting that either specimen can be used in the detection and classification of prostate cancer. In previous work, improvements in AUC values of ≥ 0.1 (3-5) have been obtained for the prediction that cancer will be found at biopsy using these specimens. In this study, we sought to assess the performance of biomarkers in predicting Gleason upgrading in cohorts of men who underwent radical prostatectomy (RP). Our sample sizes were chosen for a statistical power of greater than 90% for an AUC improvement over baseline of ≥ 0.1.

Materials and Methods

EPS specimens from were obtained by milking the urethra after an attentive DRE before the patients underwent a Robot-Assisted Radical Prostatectomy (RARP). Out of 646 men who consented under an Institutional Review Board-approved protocol for the collection and evaluation of biomarkers in EPS, 642 had complete clinical data, 224 met the 2012 NCCN criteria and 206 met the 2014 NCCN criteria for active surveillance based on their preoperative characteristics.

EPS specimen processing was as described previously (7). Standard clinico-pathologic data (age, Gleason sum, ethnicity, pre-surgical PSA, T stage, DRE and race,), direct measurements of EPS volume, total recovered RNA, and quantitative reverse transcription polymerase chain reaction values for TMPRSS2:ERG, PCA3, and PSA RNAs were obtained.

Receiver Operator Characteristic (ROC) analysis of biomarker performance was carried out in an attempt to predict upgrading. Statistical power for AUC differences attributable to biomarkers was estimated with PASS software. Minimal models for each cohort emerged from stepwise logistic regression analysis on six clinical and ten laboratory variables (Table 1).

Table 1.

Logistic regression model p-values for prognostic factors for Gleason upgrading. Univariate (UV) p-values are from single variable models. Multivariate (MV) p-values are from the final model selected from a stepwise selection procedure.

	NCCN Cohorts*
	2012 (N=224, Yes=99, No=125)		2014 (N=206, Yes=94, No=112)
Variable	UV	MV	UV	MV
Pretreatment Gleason Score
Ethnicity	.0598	.0460*	.0702	.0395*
Race	.2404		.4513
Age	.1590		.0080*	.0066*
DRE	.1026		.1462
T Stage	.0860		.0934
Prebiopsy Serum PSA	.0001**	<.0001**	.0002**	<.0001**
PCA3 RNA	.6811		.7230
PCA3 RNA/ Input RNA	.6914		.7215
PCA3 RNA/PSA mRNA	.1946		.1906
TMPRSS2:ERG	.5614		.5773
TMPRSS2:ERG/Input RNA	.5888		.5956
TMPRSS2:ERG/PSA mRNA	.5188		.5385
PSA_mRNA	.2326		.2563
PSA mRNA/Input RNA	.2356		.2320
Expressed Volume Prostatic Fluid (μL)	.7702		.5221
Total RNA in specimen (ng)	.5982		.5917

Results

For the 2012 NCCN AS cohort EPS volume, Total RNA and RNA expression biomarkers did not significantly increase the AUC value beyond the 0.6969 AUC achieved by clinical variables for ethnicity and serum PSA in the prediction of upgrading post surgery (Figure 1A). For the 2014 NCCN AS cohort, these same biomarkers failed to significantly enhance the AUC value beyond the 0.7222 value achieved with age, ethnicity and serum PSA (Figure 1B). For the 2012 cohort with complete clinical and laboratory data and sample sizes of (125 not upgraded and 99 upgraded), the power to detect an increase in the AUC of .05 and .10 was approximately 40% and 90%, respectively. For the 2014 cohort with 206 patients with complete clinical and laboratory data, the sample sizes (112 not upgraded and 94 upgraded), the power to detect an increase in the AUC of .05 and .10 is also approximately 40% and 90%, respectively.

Figure 1.

ROC for Multivariate Analysis of Biomarkers in the prediction of upgrading A. NCCN 2012 Cohort of 225 Patients. 2012 NCCN guidelines permit low and very low risk patients with a Gleason sum (GS) ≤ 6, a clinical diagnosis of T1-T2a, and a serum PSA value <10ng/ml to enter active surveillance. Patients who have less than 10 years life expectancy are permitted to enter active surveillance if they exhibit only one of the following risk factors: GS 7, or T2b-T2c or PSA 10-20. Baseline GS, serum PSA and Ethnicity gave an AUC value of 0.6969 with or without EPS volume, total recovered RNA, and quantitative reverse transcription polymerase chain reaction values for RNA expression levels from TMPRSS2:ERG, PCA3 and PSA . Patient demographics: Ethnicity: Hispanic, 6.3%; Non-Hispanic, 92%; Unknown,1.8%. Race: African American, 3.6%; Asian American,6.3% ; Caucasian American, 87.5%; American Indian,0.4%; Other, 2.2%.

B. NCCN 2014 Cohort of 206 Patients. NCCN guidelines issued in 2014 permit only low and very low risk patients with a GS ≤ 6, a clinical diagnosis of T1-T2a, and a serum PSA value <10ng/ml to enter active surveillance. Baseline GS, serum PSA, age and Ethnicity gave an AUC value of 0.7222 with or without EPS volume, total recovered RNA, and quantitative reverse transcription polymerase chain reaction values for RNA expression levels from TMPRSS2:ERG, PCA3 and PSA. Patient demographics: Ethnicity: Hispanic, 6.3%; Non-Hispanic, 91.7%; Unknown,1.9%. Race: African American, 3.9%; Asian American, 5.8%; Caucasian American, 87.8%; American Indian,0.5%; Other,1.9%.

Discussion

For NCCN AS cohorts, the AUC values achieved with standard clinical markers remained unchanged by the inclusion of biomarkers that have been successful in the prediction of biopsy outcome and upstaging. Although an increase in AUC value of 0.05 due to these biomarkers cannot be excluded, it is unlikely that such an increase would warrant the clinical use of these biomarkers in counseling patients in this setting in spite of their success in other areas of treatment. Moreover, the general concordance between results obtained with EPS specimens and those obtained with urine samples obtained after an attentive DRE argues that the results obtained with EPS will mirror those obtained with post DRE urine. We conclude that in this cohort of men, models for predicting upgrading are dominated by the standard clinicopathologic parameters with no significant contribution from current biomarkers of RNA expression or prostate function tested in EPS.