Clinical validation of an epigenetic assay to predict negative histopathological results in repeat prostate biopsies.

PURPOSE: The DOCUMENT multicenter trial in the United States validated the performance of an epigenetic test as an independent predictor of prostate cancer risk to guide decision making for repeat biopsy. Confirming an increased negative predictive value could help avoid unnecessary repeat biopsies. MATERIALS AND METHODS: We evaluated the archived, cancer negative prostate biopsy core tissue samples of 350 subjects from a total of 5 urological centers in the United States. All subjects underwent repeat biopsy within 24 months with a negative (controls) or positive (cases) histopathological result. Centralized blinded pathology evaluation of the 2 biopsy series was performed in all available subjects from each site. Biopsies were epigenetically profiled for GSTP1, APC and RASSF1 relative to the ACTB reference gene using quantitative methylation specific polymerase chain reaction. Predetermined analytical marker cutoffs were used to determine assay performance. Multivariate logistic regression was used to evaluate all risk factors. RESULTS: The epigenetic assay resulted in a negative predictive value of 88% (95% CI 85-91). In multivariate models correcting for age, prostate specific antigen, digital rectal examination, first biopsy histopathological characteristics and race the test proved to be the most significant independent predictor of patient outcome (OR 2.69, 95% CI 1.60-4.51). CONCLUSIONS: The DOCUMENT study validated that the epigenetic assay was a significant, independent predictor of prostate cancer detection in a repeat biopsy collected an average of 13 months after an initial negative result. Due to its 88% negative predictive value adding this epigenetic assay to other known risk factors may help decrease unnecessary repeat prostate biopsies.

The epigenetic promise for prostate cancer diagnosis.

BACKGROUND: Prostate cancer is the most common cancer diagnosis in men and a leading cause of death. Improvements in disease management would have a significant impact and could be facilitated by the development of biomarkers, whether for diagnostic, prognostic, or predictive purposes. The blood-based prostate biomarker PSA has been part of clinical practice for over two decades, although it is surrounded by controversy. While debates of usefulness are ongoing, alternatives should be explored. Particularly with recent recommendations against routine PSA-testing, the time is ripe to explore promising biomarkers to yield a more efficient and accurate screening for detection and management of prostate cancer. Epigenetic changes, more specifically DNA methylation, are amongst the most common alterations in human cancer. These changes are associated with transcriptional silencing of genes, leading to an altered cellular biology. METHODS: One gene in particular, GSTP1, has been widely studied in prostate cancer. Therefore a meta-analysis has been conducted to examine the role of this and other genes and the potential contribution to prostate cancer management and screening refinement. RESULTS: More than 30 independent, peer reviewed studies have reported a consistently high sensitivity and specificity of GSTP1 hypermethylation in prostatectomy or biopsy tissue. The meta-analysis combined and compared these results. CONCLUSIONS: GSTP1 methylation detection can serve an important role in prostate cancer managment. The meta-analysis clearly confirmed a link between tissue DNA hypermethylation of this and other genes and prostate cancer. Detection of DNA methylation in genes, including GSTP1, could serve an important role in clinical practice.

Evaluation of GSTP1 and APC methylation as indicators for repeat biopsy in a high-risk cohort of men with negative initial prostate biopsies.

UNLABELLED: Study Type - Diagnostic (exploratory cohort) Level of Evidence 2b What's known on the subject? and What does the study add? Hypermethylation of genes such as glutathione-S-transferase P1 (GSTP1) and adenomatous polyposis coli (APC) occurs with high frequency in prostate tumour tissue but is much less common in the benign prostate; however, the potential value of gene methylation biomarkers as an adjunct to biopsy histopathology has had little study. When measured in histologically benign prostate biopsy tissue, APC gene hypermethylation was found to have high negative predictive value and high sensitivity. GSTP1 hypermethylation was found to have lower performance than APC. OBJECTIVE: To evaluate the performance of DNA methylation biomarkers in the setting of repeat biopsy in men with an initially negative prostate biopsy but a high index of suspicion for missed prostate cancer. PATIENTS AND METHODS: We prospectively evaluated 86 men with an initial histologically negative prostate biopsy and high-risk features. All men underwent repeat 12-core ultrasonography-guided biopsy. DNA methylation of glutathione-S-transferase P1 (GSTP1) and adenomatous polyposis coli (APC) was determined using tissue from the initially negative biopsy and compared with histology of the repeat biopsy. The primary outcome was the relative negative predictive value (NPV) of APC compared with GSTP1, and its 95% confidence interval (CI). RESULTS: On repeat biopsy, 21/86 (24%) men had prostate cancer. APC and GSTP1 methylation ratios below the threshold (predicting no cancer) produced a NPV of 0.96 and 0.80, respectively. The relative NPV was 1.2 (95% CI: 1.06-1.36), indicating APC has significantly higher NPV. Methylation ratios above the threshold yielded a sensitivity of 0.95 for APC and 0.43 for GSTP1. Combining both methylation markers produced a performance similar to that of APC alone. APC methylation patterns were consistent with a possible field effect or occurrence early in carcinogenesis. CONCLUSIONS: APC methylation provided a very high NPV with a low percentage of false-negatives, in the first prospective study to evaluate performance of DNA methylation markers in a clinical cohort of men undergoing repeat biopsy. The potential of APC methylation to reduce unnecessary repeat biopsies warrants validation in a larger prospective cohort.

Reduced Rate of Repeated Prostate Biopsies Observed in ConfirmMDx Clinical Utility Field Study.

BACKGROUND: The diagnosis of prostate cancer is dependent on histologic confirmation in biopsy core tissues. The biopsy procedure is invasive, puts the patient at risk for complications, and is subject to significant sampling errors. An epigenetic test that uses methylation-specific polymerase chain reaction to determine the epigenetic status of the prostate cancer-associated genes GSTP1, APC, and RASSF1 has been clinically validated and is used in clinical practice to increase the negative predictive value in men with no history of prostate cancer compared with standard histopathology. Such information can help to avoid unnecessary repeat biopsies. The repeat biopsy rate may provide preliminary clinical utility evidence in relation to this assay's potential impact on the number of unnecessary repeat prostate biopsies performed in US urology practices. OBJECTIVE: The purpose of this preliminary study was to quantify the number of repeat prostate biopsy procedures to demonstrate a low repeat biopsy rate for men with a history of negative histopathology who received a negative epigenetic assay result on testing of the residual prostate tissue. METHODS: In this recently completed field observation study, practicing urologists used the epigenetic test called ConfirmMDx for Prostate Cancer (MDxHealth, Inc, Irvine, CA) to evaluate cancer-negative men considered at risk for prostate cancer. This test has been previously validated in 2 blinded multicenter studies that showed the superior negative predictive value of the epigenetic test over standard histopathology for cancer detection in prostate biopsies. A total of 5 clinical urology practices that had ordered a minimum of 40 commercial epigenetic test requisitions for patients with previous, cancer-negative biopsies over the course of the previous 18 months were contacted to assess their interest to participate in the study. Select demographic and prostate-screening parameter information, as well as the incidence of repeat biopsy, specifically for patients with a negative test result, was collected and merged into 1 collective database. All men from each of the 5 sites who had negative assay results were included in the analysis. RESULTS: A total of 138 patients were identified in these urology practices and were included in the analysis. The median age of the men was 63 years, and the current median serum prostate-specific antigen level was 4.7 ng/mL. Repeat biopsies had been performed in 6 of the 138 (4.3%) men with a negative epigenetic assay result, in whom no evidence of cancer was found on histopathology. CONCLUSION: In this study, a low rate of repeat prostatic biopsies was observed in the group of men with previous histopathologically negative biopsies who were considered to be at risk for harboring cancer. The data suggest that patients managed using the ConfirmMDx for Prostate Cancer negative results had a low rate of repeat prostate biopsies. These results warrant a large, controlled, prospective study to further evaluate the clinical utility of the epigenetic test to lower the unnecessary repeat biopsy rate.

Prostate cancer detected by methylated gene markers in histopathologically cancer-negative tissues from men with subsequent positive biopsies.

The goal of this retrospective, multicenter study was to evaluate the ability of a newly developed refinement of a quantitative methylation-specific PCR assay to detect prostate cancer in histopathologically negative biopsy samples collected from men who were later positively diagnosed during a follow-up biopsy procedure. Biomarkers tested in the assay included the much-studied glutathione-S-transferase P1 gene and others reported to be frequently methylated in prostate cancer. Core biopsy tissue from subjects with serial negative biopsies served as a negative control to assess assay specificity. As a positive control, biopsy core tissue from patients histopathologically diagnosed with prostate cancer was used to gauge true marker sensitivity in known cancer-containing specimens. Testing was completed in 971 archived paraffin-embedded tissue blocks from 264 men screened for prostate cancer. More samples were initially tested, but due to the advanced age of the paraffinized tissue, DNA quality for quantitative methylation-specific PCR analysis was insufficient in 34% of the available blocks. The glutathione-S-transferase P1 gene has been confirmed as a powerful indicator of the presence of prostate cancer cells. A sensitivity of 52% was observed in the "potentially false-negative first biopsies," with a corresponding specificity of 85% and the sensitivity in biopsy tissue cores containing histopathologically confirmed prostate cancer was 95%. An even higher sensitivity can be reached with RAR-2beta (84%) and APC (72%), with respective specificities of 48% and 50%. Gene methylation was detected in initial, negative biopsy tissue in men who were later diagnosed with prostate cancer. Testing for methylation in histopathologically negative biopsies could improve the early detection of prostate cancer.